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Mystery vacuum leak?

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Big Bird View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Topic: Mystery vacuum leak?
    Posted: 21-September-2014 at 2:34AM
Glad to hear you found the culprit.
"What we do in full frontal view, is more honest than your cleaned-up mind."
Randy
1979 T-Bird
2005 F-150 STX RCSB 4.6, 3.55 LSD
How the Heck does a REGULAR CAB SHORTBED weigh over 5200 pounds?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 20-September-2014 at 5:07PM
Clap awesome les, glad you got it fixed Big smile
JOHN
74 GRAN TORINO S&H CLONE
74 VETTE CUSTOM
90 S10 BLAZER 4X4 LIFTED
77 CELICA CUSTOM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedway 650 Quote  Post ReplyReply Direct Link To This Post Posted: 20-September-2014 at 3:22PM
Big smile
  I drove the car 55 miles today, and it ran perfectly!
 
   I took the car to a show at a local fairgrounds, running hills and curves through the sticks going and highway returning. In between were three stops of various durations. There was never a beat missed. The thing has never run better in the 15 years that I have owned it.
 
  The culprit was finally isolated to be likely what it eventually proved to be...the Pertronix Ignitor II had failed. Not only did it do so well under the 30 month warranty period, but it was likely bad from the time it was installed. Unfortunately, due to the nature of the malfunction and the fact the issue acted like so may other things, plus the significant amounts of time that passed when I was not seeking to find the problem, any coverage on the part has expired by now. I guess I just assumed an electronic ignion part would just quit, or at least act like a failing ignition part every time when hot. None of this only sometimes, only at idle, usually when in gear, sometimes at shift bit. It looks like the issue that acted like a vacuum leak, the one that acted like lazy timing, and the one that replicated a mixture issue were all various effects of one part that kind of worked, sometimes.
 
  I would like to thank several of you that helped me with advice and links to advice in dealing with these issues! I love this site. Hopefully, someday in a search, somebody will read through this thread and find their answer a lot easier than I did.
 
  -Les in MI.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 15-September-2014 at 4:27PM
it very well could be the electronic pick up in the dist. i had a weak one in my ford courier, ran ok but tiny bit of smoke when idling, performance was down slightly, it would come and go, so i replaced that part and it still runs HARD! it'll smoke any similar equipped ranger!
JOHN
74 GRAN TORINO S&H CLONE
74 VETTE CUSTOM
90 S10 BLAZER 4X4 LIFTED
77 CELICA CUSTOM
75 V8 MONZA SUPERCHARGED
79 COURIER VERT. SLAMMED
75 VEGA V6 5 SPD
70 CHEV C10 P/U
68 MUSTANG FB CONVERSION
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kychevyguy Quote  Post ReplyReply Direct Link To This Post Posted: 15-September-2014 at 11:41AM
...and the dude in Kentucky is still following along. Smile
JT, USAF Ret./Architect
1971 Ford F100 "Lizzy"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedway 650 Quote  Post ReplyReply Direct Link To This Post Posted: 15-September-2014 at 10:46AM
  I just ordered both a new Ignitor II and accompanying coil. At this point, I am 90 percent sure the issue is the part in the distributor. The resistance on the coil was exactly what it was supposed to be, both cold and hot. The power was 13.4 to the coil when the engine was running, and never dropped below 11.7V even as the engine is chugging away at 200-300 rpms misfiring like crazy.
 
  I did check ground resistance  and found it to be very high. The ignition mfgr. recommended no more than .2 ohms from the mounting plate of the module to the battery ground. It was over 2 ohms high, and I ended up running a new ground jumper from the distributor body (vacuum advance screw) to a ground post on the alternator, which had no measurable resistance to the battery negative. Bingo. Perfectly grounded ignition. As unlikely as that small detail seemed, I thought I had nailed the issue down. The 1-2 full power shift was perfectly clean and hard several times, without stumble or cough. Even after 30 minutes of running around a warmed up engine, no issues. Then, just before I was going to back it back in to the garage and go to work, the misfire returns.
 
  It isn't supplied voltage to the coil. It isn't ground issues anymore. It don't seem to be coil, but I am getting another one to change, as well. It has to be the Ignitor, which, it would appear, never has worked right for me. So, I have almost $150 in parts coming to fix the car for (hopefully soon) somebody else. A guy is coming tomorrow to see it from less than 20 miles away, but he is kind of scared of the roof rust and I told him I was still messing with THE ISSUE. I kind of doubt he'll buy it, but there is this dude in Kentucky..........
 
  -Les in MI.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote aquartlow Quote  Post ReplyReply Direct Link To This Post Posted: 14-September-2014 at 9:43AM
Originally posted by Speedway 650 Speedway 650 wrote:

  Chasing potential issues with 40+ year old wiring....it don't get much better than that. I can hardly wait. I was thinking of skipping church to get started sooner. On the other hand, I had better not take any chances. I need all the help I can get, so going to church might be a better start to my Sunday.
 
  The Flamethrower coil is mounted on its side in the stock mounting bracket.
 
  -Les in MI
 
Some coils (by design)have heat related issues when they are side mounted(the internal windings aren't fully immersed in the oil that is inside the coil). Don't know if this could be the answer to your issue or not, try mounting the coil in an upright position and see what happens. Just a thought.
 BTW, for your sake I hope you didn't skip church today to "get a jump" at dealing with this, the man above is the best person to have on your side. Good luck. Todd


Edited by aquartlow - 14-September-2014 at 9:46AM
www.supermotors.net/22468
Yeah, It's a Hybrid...It burns gas and tires.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 14-September-2014 at 7:51AM
Look at the pertronix unit for heat soak problems, check the wires in the distributor that feed the pertronix unit (Breaker plate moves with mech., and vac. advance) and see if the motion has broken a wire or loosened a connection, sub in a different coil and try to duplicate the problem.
"What we do in full frontal view, is more honest than your cleaned-up mind."
Randy
1979 T-Bird
2005 F-150 STX RCSB 4.6, 3.55 LSD
How the Heck does a REGULAR CAB SHORTBED weigh over 5200 pounds?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kychevyguy Quote  Post ReplyReply Direct Link To This Post Posted: 14-September-2014 at 6:13AM
Les,
 
Sounds like it just needs to breath some Kentucky air...Big smile
JT, USAF Ret./Architect
1971 Ford F100 "Lizzy"
1971 Cougar XR7 "Kitty"
1984 Chevy Silverado "Sylvia"
2009 Smart Fortwo Cabrio "Lil Dude"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fordpower Quote  Post ReplyReply Direct Link To This Post Posted: 14-September-2014 at 3:47AM
Had a sim problem yr. ago with my 57 0n











Had a problem like that yr. ago.It was the coil.





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedway 650 Quote  Post ReplyReply Direct Link To This Post Posted: 14-September-2014 at 3:10AM
  Chasing potential issues with 40+ year old wiring....it don't get much better than that. I can hardly wait. I was thinking of skipping church to get started sooner. On the other hand, I had better not take any chances. I need all the help I can get, so going to church might be a better start to my Sunday.
 
  The Flamethrower coil is mounted on its side in the stock mounting bracket.
 
  -Les in MI
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Post Options Post Options   Thanks (0) Thanks(0)   Quote aquartlow Quote  Post ReplyReply Direct Link To This Post Posted: 14-September-2014 at 1:08AM
  It is a good idea to connect a test light to the wire that powers the Petronix ignition, you can see if power is interrupted, causing your issues. Sounds like the coil is another area to diagnose, "breaking down" due to heat(is the coil mounted straight up or on it's side)? As California Johnny advised, there could be an internal break in one of the wires. The broken wire could either be found in one(or more) of the wires coming from the battery/starter solenoid/distribution stud, behind the dash or under the hood. As the engine heats up a typical alternator (in good condition)will have a reduction in output, the amount of power output reduction depends on how hot an engine runs(usually only .5 volt or so, not a big loss, but it does happen). Your symptoms reminds me of a Duraspark box going bad, usually only has or shows issues when hot. Re-check as many electrical connections as possible, especially your grounds. Hope this helps. Todd
www.supermotors.net/22468
Yeah, It's a Hybrid...It burns gas and tires.

No matter how good she looks, somebody, somewhere, is tired of her sh*t.

Beauty is skin deep, ugliness goes clear to the bone.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 13-September-2014 at 9:41PM
you're on the right track, that's exactly what i'm thinking!
JOHN
74 GRAN TORINO S&H CLONE
74 VETTE CUSTOM
90 S10 BLAZER 4X4 LIFTED
77 CELICA CUSTOM
75 V8 MONZA SUPERCHARGED
79 COURIER VERT. SLAMMED
75 VEGA V6 5 SPD
70 CHEV C10 P/U
68 MUSTANG FB CONVERSION
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedway 650 Quote  Post ReplyReply Direct Link To This Post Posted: 13-September-2014 at 7:55PM
  The timing light was used on all wires. The spark was either there on all wires when the engine was running well, or going away on all of the various cylinders checked when running poorly. This is an all or nothing situation, as far as I can tell, and not where only a few cylinders are dropping. When using the light on the timing, the pointer was consistently where it should be and not jumping around.
 
  What it acts like is happening is the spark goes away, and the engine is basically dieseling at idle when it does. In fact, anyone who has ever had timing or compression a bit too hot for their grade of fuel knows exactly what this acts like. It can do it for 30 seconds or more at a time, then clear up.
 
  My next plan of action is to see if I am getting consistent and clean 12 volts to the ignition both when the engine is running well and when hot and misfiring. If voltage is fluctuating, maybe a voltage regulation issue is causing the spark issue and the aftermarket ignition components are alright. If the voltage is steady at about 12V, I will attempt to get the manufacturer to replace components.
 
  Thanks again for the interest and advice.
 
  -Les
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mkshelton Quote  Post ReplyReply Direct Link To This Post Posted: 13-September-2014 at 7:00PM
I hAve seen worn distributer gears cause this too. Was the timing steady or did the marks appear to dance around at the pointer?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 13-September-2014 at 6:04PM
i'm still following this les, and i do remember the holiday inn ads! try using the timing light on each plug wire to see if it's just one or two wires or if it's all of the ignition circuit, could be the coil or the module unit, or maybe the power wire to the coil has a internal break, or the ignition switch loosing contact??? i think with the timing light going out, may have just given you a major clue!Shocked
JOHN
74 GRAN TORINO S&H CLONE
74 VETTE CUSTOM
90 S10 BLAZER 4X4 LIFTED
77 CELICA CUSTOM
75 V8 MONZA SUPERCHARGED
79 COURIER VERT. SLAMMED
75 VEGA V6 5 SPD
70 CHEV C10 P/U
68 MUSTANG FB CONVERSION
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedway 650 Quote  Post ReplyReply Direct Link To This Post Posted: 13-September-2014 at 5:41PM
  Do I still have anyone following the saga of the world's most elusive tuning bug on what should be a pretty great running car?
 
  Today, I struggled with the tuning issue again. I was armed with two new "tools". One was a vacuum pump/gauge. The other, for part of the time, was my brother. He is a more accomplished auto mechanic than I. On his list of successful feats are major engine, transaxle, transmission, HVAC, and suspension overhauls and conversions on many mostly late model vehicles for himself and others. He is not a professional...but he does often stay at a Holliday Inn Express (for work). Remember those ads? I loved them. But, seriously, I needed new eyes and ears. But, being younger than me, he is used to being able to plug a computer in to the vehicle to diagnose misfires and faulty components. He lets the scanner find the issue and he fixes it. We'd get to see if he cold "old school" bug kill.
 
  To answer the last post, the carburetor was on another car and ran great on it. It had previously run great on this one.  But I had run in to a previous issue with this car that came and went for some time, both before and after the carb was rebuilt. I am not running points and condenser. It was my other car that lost two condensers in a few hundred miles. This one had a Pertronix electronic put on it a couple of years ago, or maybe 500 miles ago. See my new hypothesis below....
 
  The findings:
 
  The car started cold perfectly, and warmed up like it should. It run at 800 rpms for like a half hour with vacuum needle rapidly, but steadily moving between 19 and 19.5". If the gas was punched, it would drop to nearly nothing and flash back over 25 before returning to the same place. Eventually, after close to an hour, the stumble showed it's self. Only intermittently and it never stalled, but would come close, only to clear. Sometimes, a little gas would clear it, and sometimes it went away on it's own. We messed with the isolation and testing of the EGR and vacuum advance, as well as trying to figure out and test various temperature switches and one way valves. No part failed to work as expected in isolation and nothing removed affected the running or vacuum readings in an unexpected way.
 
  Then the timing light came out. While checking timing to see if something slipped, it stumbled, and the light went out. HUH?! That's right. Whenever the engine started to miss, spark was either very irregular or momentarily absent. After seeing good spark at all 8 wires when the engine was running well again, we went with the new theory an ignition issue has been causing all of this, and not a leaky or faulty vacuum situation as first thought or a fuel delivery/regulation issue as I next thought a possibility. Spark always went away when the rough running happens, even though the engine doesn't stop running. We had to stop for today before the ignition components could be checked.
 
   Again, this issue only happens when the engine has been thoroughly warmed up for some time, at idle or low rpms, and still comes and goes relatively at random then, but is often triggered by shifting a load on to the engine. Yet, it rarely stalls and never fails to restart. Tomorrow, I plan to test the voltage to the ignition, and watch carefully what it does when the running issue inevitably returns. I will test the resistance of the Pertronix Ignitor II unit and it's coil, and see if anything there changes when hot.
 
  Back up top, I said I had installed a new ignition with more about that later. Well, some kind of ignition issue developed soon after the electronic ignition was installed, but not right after it. It would stall hot and idle poorly. Initially, I replaced the EGR, as someone suggested that the symptoms were consistent with a faulty one. No fix. I then chased the resistance wire and eliminated it, as the new ignition is made to work without one, but I initially left it because I got from somewhere it would work either way. Leaving the factory resistance wire in was both easier and allowed a quick field swap to points if I  needed to. This made the issue go away, or so I thought. I just returned. Had the electronic ignition started to fail due to insufficient voltage in the past or due to some other past or current reason? Why is it so hit an miss? Why pretty much only at idle and hot? Could that "cough" at full throttle shift also be the ignition? The darned carb and timing act almost spot perfect?
 
  -Perpetually challenged in MI.
 
 


Edited by Speedway 650 - 13-September-2014 at 5:54PM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 10-September-2014 at 10:11AM
Did your problems start after you changed any parts, like the carb... You said it worked fine on the Gran Torino? If you changed anything shortly before the problem started, you should look at that as a potential culprit. Also try putting a vacuum gauge in it. I'm thinking vacuum leak, and if you unhooked and capped the vacuum lines and didn't stop the problem, I would look at an intake leak, (same bolt system as 302/351W, factory recommends retorque every 30k miles) or if you recently changed the carb, the carb base gasket. If the vacuum gauge doesn't help pin it down, try a compression check.
One other thought: are you running points...a bad condenser can FEEL like a vacuum issue when driving, and will give you a lack of performance? If you have points, this would be the first thing I would check.
"What we do in full frontal view, is more honest than your cleaned-up mind."
Randy
1979 T-Bird
2005 F-150 STX RCSB 4.6, 3.55 LSD
How the Heck does a REGULAR CAB SHORTBED weigh over 5200 pounds?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedway 650 Quote  Post ReplyReply Direct Link To This Post Posted: 09-September-2014 at 4:26PM
Originally posted by SPLUHAR SPLUHAR wrote:

Disconnect the main vacuum hose to the vacuum manifold on the firewall and plug that hose.  It'll eliminate all of the vacuum hoses for power brakes and whole under-dash.  If the vacuum leak goes away, you know it has something to do with what you just un-hooked, and you can plug it back in, and go about unhooking and plugging individual systems to track down exactly what's causing it.  If there's no change, now you know it's at the carb or manifold.  Then you can use carb cleaner to find it exactly.
 
 
  Update on the tuning issue. I did just what was posted above. I plugged all three small fittings and the large brake booster hose from the rear of the manifold. All I had left to plug was a line in to the EGR from the unplugged connector on the firewall to completely isolate the engine from outside vacuum.
 
  I started the car and warmed it up completely. No symptoms. With full knowledge of the lack of power assist to the brakes or vacuum shifts, I went for a test drive in the country. Almost all was well until I returned to back in to the driveway. It stumbled and tried to die. I blipped the gas a bit and it run better for a few moments. A couple of applications of this and it idled fine in or out of gear...for a couple of minutes, then the rough running. Often, putting the car in to gear triggered it, but it would eventually do it out of gear, as well. A little stab at the gas peddle would keep the engine from stalling and raise the rpms back to idle more smoothly again. Also noteworthy: When completely hot, if I shut the car off, it generally requires a pump of gas to restart. I guess I will have to check the carburetor out, again. It must have developed some issue since it was on the Gran Torino.
 
  While likely a different issue, I did note there is still a cough or even backfire when I make a full power 1-2 shift. That occurs at 4600-4800 rpms. It doesn't happen every time, but more often than not. When the vacuum modulator was unplugged, it shifted cleanly every time at 4000 rpms. Anything other than that full power first shift is smooth, but it coughs there. Lean? Where is valve float on a 40 year old 400 Ford? I installed a new vacuum modulator when I first messed with this running issue. I can't remember where it used to shift before. It isn't over revving a bit, is it? There is an adjusting screw in the modulator nipple, but I can't adjust it with the stupid thing in the transmission, due to it being aimed directly at the crossmember, with just enough room to push the hose on.
 
  I used to think I was a half competent mechanic, but these little bugs this car has developed are starting to make it appear otherwise. As has been the case since the top of this thread, all help is enthusiastically welcome!
 
  -Les
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SPLUHAR Quote  Post ReplyReply Direct Link To This Post Posted: 03-September-2014 at 7:41AM
Disconnect the main vacuum hose to the vacuum manifold on the firewall and plug that hose.  It'll eliminate all of the vacuum hoses for power brakes and whole under-dash.  If the vacuum leak goes away, you know it has something to do with what you just un-hooked, and you can plug it back in, and go about unhooking and plugging individual systems to track down exactly what's causing it.  If there's no change, now you know it's at the carb or manifold.  Then you can use carb cleaner to find it exactly.
 


Edited by SPLUHAR - 03-September-2014 at 7:43AM
1976 ELITE, 71 429 w/cam, quadrajet, 4 wheel Mark V disc brakes, 3.25 trac lok, gutted & 12.9'd Mustang steering box
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wideone Quote  Post ReplyReply Direct Link To This Post Posted: 03-September-2014 at 2:12AM
Power Brakes?  Check the hose and fittings.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote spuninmo Quote  Post ReplyReply Direct Link To This Post Posted: 03-September-2014 at 1:06AM
I am having an issue similar with My 351...I put on an offenhauser intake and had a carb freshly rebuilt for it.  Turns out the intake didnt quite seal right with the valley pan and it has to come off and a new, different intake set without the valley pan has to be used...something about aluminum intakes and the valley pan not being compatible due to thermal expansion differences of aluminum and iron.  Anyhoo, I was chuffing through the carb at startup, and idling rough, but once it was in gear it seemed to run nicely at an elevated RPM, allowing it to idle back down, the roughness would start again, like it wanted to stall but it stayed running.  When I would go from a higher RPM to an idle at times it would load up and backfire.  Turns out Mine is a combination of issues...the intake not properly sealing is creating a vacuum leak on the underside of the intake, so the ether spray didnt detect it and the carb being too aggressively jetted...slap a vacuum gage on it and check your readings...I was pulling 16 at idle, but when in gear I was pulling 8, the idle was set at 575 as per My ford book, and it would fluctuate slowly from 525-575.  All this indicated a manifold/carb vacuum issue.  Its a long process of elimination, but eventually you will get there
Larry, KCMO

1972 8 year long never ending uphill battle would have been better off getting that root canal Gran Torino
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kychevyguy Quote  Post ReplyReply Direct Link To This Post Posted: 03-September-2014 at 12:34AM
Hey Les,
 
Did you have a good vacation in the UP?
 
I understand your frustration with the vacuum system. Tracing that down can be a real bear. However, I am still interested in your merc.
 
JT, USAF Ret./Architect
1971 Ford F100 "Lizzy"
1971 Cougar XR7 "Kitty"
1984 Chevy Silverado "Sylvia"
2009 Smart Fortwo Cabrio "Lil Dude"
2015 Volvo XC60 R-Design "Sven"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fordpower Quote  Post ReplyReply Direct Link To This Post Posted: 03-September-2014 at 12:11AM
After removing all the smog sh. mine idles up and down about 2 or 3 hundred. Also can hear a hiss or whisle.Brother in law thinks it is the carb.Also it now is sending smoke sig.out the breathers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedway 650 Quote  Post ReplyReply Direct Link To This Post Posted: 02-September-2014 at 5:23PM
  I should get a chance tomorrow to mess with the Merc again. Thanks for the input. I'll try to spray a bit of carb cleaner around the  various leak possibilities, if I can keep it running in gear to do that. That will require the help of my wife, who will be kid-free for the first time this summer.
 
  Before I start spraying, I will check all of the nuts and bolts, first. The engine is a 400, completely stock. I can't hear a leak anywhere and I would describe the problem as somewhat consistent in when and how it shows up, but still intermittent.
 
  -Les
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 01-September-2014 at 4:04AM
Which engine is in the car? 302/351W intake bolts lose torque and can cause intermittent vacuum leaks under the intake (lifter valley).
Unless it leaks water too, you can usually snug up the bolts and fix the problem.
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How the Heck does a REGULAR CAB SHORTBED weigh over 5200 pounds?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote aquartlow Quote  Post ReplyReply Direct Link To This Post Posted: 01-September-2014 at 12:54AM
This may be far fetched but here goes: On some Ford/Lincoln/Mercury's they have a vacuum operated release for the parking brake, this type of release is built into the back-up light actuator that is attached to the base of the steering column near the firewall rubber boot. Here is a pic,
  72-THUNDERBIRD-NOS-FORD-D2SZ-15520-C-SWITCH-BACK-UP-LAMP
This back-up switch will work with a manual release parking brake, just don't need the vacuum hoses attached. The way this switch works is when the shifter is changed from P to R and/or D, there is a port that is uncovered inside the mechanism that sends a vacuum signal(via engine vacuum source) to the parking brake's vacuum release actuator. Here is a pic of a vacuum release parking brake,
1975-78-LINCOLN-CONTINENTAL-NOS-Parking-brake-assy
 
Your Montego shouldn't have come stock with the vacuum release back-up switch (or parking brake assembly), but someone might have replaced it with the vacuum type for whatever reason. Just give it a look-see under the dash at the base of the steering column near the rubber boot. Once again, this sounds far-fetched and a stretch, but could explain the vacuum leak issues when in gear. Hope this helps in some way. Good luck. Todd
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smhj Quote  Post ReplyReply Direct Link To This Post Posted: 31-August-2014 at 11:09PM
Make sure PCV valve and tube is clear.
73MONTEGO
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 31-August-2014 at 9:16PM
when it's idling rough, spray carb cleaner, wd-40, even water in a squirt bottle will work, spray around the base of the carb, and any vacuum hoses, if you get any change in engine RPM's check that area closer for your leak
JOHN
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Speedway 650 Quote  Post ReplyReply Direct Link To This Post Posted: 31-August-2014 at 8:21PM
  While I have now diagnosed and addressed a question about oil pressure in my Merc, I still have a bug to kill before I can expect to hook a buyer.
 
  When the car starts, cold or hot, it runs pretty well. Sometimes, and only sometimes, mind you, it will start to cough and run rough. The issue does seem to be more prevalent when hot. If it is put back in P or N, it begins to run more smoothly in almost immediately. I changed the vacuum modulator in the C-6 transmission, thinking that was the only gear dependent source of a vacuum leak. I thought that had fixed it, but after a drive today, I had to play with the gas to get it to stay running while I backed in to the tight garage. I thought brake booster, but holding the brake down in P or N doesn't cause the condition. Of coarse, an old car guy from here in town has interest in the car, and he took it for a decently long test drive this evening. When he brought it back, he commented on how well it goes down the road, but it was sputtering and trying to stall when he pulled it in. It has a vacuum leak somewhere", he said. I never mentioned that term to him. Therefore, we agree of what the issue acts like, but where and what could be leaking? It acts like a car did when I forgot the hose from the PCV valve to the carb once, but not quite as bad. Something, somewhere is sucking air and killing idle....in gear.
 
  I dislike vacuum systems as much as I dislike wiring.
 
  When it is running like it did when I took it out this morning, it runs really well. As I was retuning home from that first drive today, I wondered again if I was selling the right car. My Gran Torino just don't have that kind of guts. Then the frustration returned.
 
  Note to a couple of guys on here that expressed interest in the car a couple of weeks ago: I goes down the road really well. I am actively trying to tune it a bit better before I push to sell it again.
 
  -Les in MI.
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