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  #16  
Old 03-24-2005, 04:43 PM
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yo my prob was a miss fire do to a bad coil pack but car ran like crap. the car ran rough all the way to the 3 shift to drive. once in drive the car would shudder and shake. i guess do to the lower rpms. no really bad shakes during take off. but my car is in the mist of getting fixed waiting on part(coil pack). other than that my svx has been a solid machine. no other problem and very health. 97 red
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  #17  
Old 03-24-2005, 08:21 PM
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p.s.

A leak in the intake duct between the MAF and the t-body can also cause the same problem.
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  #18  
Old 03-25-2005, 05:05 PM
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I have so much home repair stuff that it will be weeks before I can turn attention to much more. I am learning to drive to minimize the problem.

Anyway, I can easily check for a ruptured air intake tube - what 30 seconds?

How would the car react if the EGR was stuck open in an intermediate spot?
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  #19  
Old 03-25-2005, 07:58 PM
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Like a real bad vacuum leak - first there is, well, the vacuum loss. Then there is the introduction of an inert gas...
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  #20  
Old 03-26-2005, 04:19 AM
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Beav,

could a faulty IAC valve cause, or contribute to misfires or rough running?

my car (if not warmed up a few minutes on a COLD start) will run rough for a little bit (or misfire on cyl #1 if no warmup, and especially if going up a big hill, which i have to do after work.)

i have -replaced and set TPS correctly
-replaced coil pack #1
-replaced all spark plugs w/factory ones
-replaced temp sensor
-cleaned (gently!) the MAF
-cleaned TB and IAC

noticed a "slight change" after cleaning the IAC, but problem persists. when it was off, i noticed the IAC was at its 'maximum' as far as adjustment goes. time for a new one?
this is definitely a temperature-related/idle problem. the only other thing i could think of is that its an injector, or the ECU, but wouldn't the car run bad ALL the time if that were the case? the trouble only happens within the first few minutes - after its warmed up (or in warmer weather) its fine. ?????!!!?!!?!!????
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  #21  
Old 03-26-2005, 06:32 AM
comp_jas comp_jas is offline
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I'm still with you Landshark, same problem

I read a post Beav wrote about EGR porting but haven't really thought it through yet.

I threw a CE light Thursday after two months of no problems.
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  #22  
Old 03-26-2005, 10:22 AM
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No, the IAC won't cause a misfire. It only adjusts the idle speed, nothing more.

Sounds as though you may have an injector that is leaking down a bit overnight. When first started the excess fuel in one cylinder will cause a miss until it clears out. Normally it should only take a few seconds to clear out, any more than that and you probably have a different problem. You might try some Techron, but don't go crazy with it. If the first dose doesn't do the trick adding more probably won't either. Remember Moore's Law.

There is no way to observe the IAC in action. It only moves when directed by the ECU. It is in a constant state of motion during operation, it doesn't just sit in one spot. It does move such a small amount, and very quickly at that, that even if you were able to observe it you may not even see it moving.

If the problem takes longer than a few seconds I'd be taking a close look at the coils and their boots. A little condensation when cold on the plug, boot or coil tower could cause a misfire until warm enough to evaporate the moisture.
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  #23  
Old 04-03-2005, 07:44 PM
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back to ground zero after finding the prob. with the misfire in cyl 4. taking to the shop and having a new coil pack put on. the coil pack was shot. replace and same problem is coming back. when car was pick up it ran like new. now a week later i get a ce light. i clear it and car is still running like new. 2 days later i get it again and car is slowly getting worse with a definate missfire. no clouds of smoke. can some one help explain. could this be something with the ignighter or injectors. i starts gradualy and ends up bad.
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  #24  
Old 04-03-2005, 10:34 PM
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my coil pack (and spark plugs) were replaced and no change.

i'll be replacing the injector this week and will report the results......
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1987 928 S4 (Black) SOLD!
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1987 928 S4 (Black) SOLD!
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  #25  
Old 04-04-2005, 04:46 PM
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took it back to the shop and got ce checked out. it was a o2 due to exhaust set up and crappy running. so i took the car myself in 30 degree weather and pulled #4 cyinder plug and it was fowled out in left field. i replaced the plug my fuel filter(which made a big difference) and air filter and car runs better than it has ever ran. the fix made my exhaust quiet down alot and improve proformance dramaticly. low end and high end. i seem to recall rumors of loss of low end do to a simalar set up like i got. not true. the o2 will not come back on either.
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  #26  
Old 04-14-2005, 06:11 PM
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Been very busy with house repairs - have a minor update and a question.

Tried swapping the TPS with a spare I had (bought in a lame attempt to fix tranny 2-3 shift flare), no change - assume problem is elsewhere.

Re-checked MAF sensor connection and air intake tract, found a small hole where a hose on the driver's side connects to the plastic housing - bottom of two hoses near where it connects to the throttle body (part of the PCV system I think). Fixed that - tiny, tiny improvement.

Tried to test the EGR valve by putting a vacuum on the valve - couldn't get to more than about 5", but engine stumbled a bit, so I'm assuming EGR is functional.

Interested that I couldn't get a decent vacuum, I did some close listening (at idle), and I heard what sounds like an air leak.

Took the top black pieces off the intake manifold and it definitely sounds like an air leak somewhere under the manifold - loudest when I put my ear near the opening where the PCV valve is located.

I wish I could remember what it should sound like....So, my question - is this air leak sound normal, or do I need to pull the manifold & replace hoses, etc.?
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  #27  
Old 04-14-2005, 06:40 PM
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Quote:
Originally Posted by lee
Re-checked MAF sensor connection and air intake tract, found a small hole where a hose on the driver's side connects to the plastic housing - bottom of two hoses near where it connects to the throttle body (part of the PCV system I think). Fixed that - tiny, tiny improvement.

Any leak between the MAF and the engine will cause a problem, be sure you don't have more leaks. Sometimes it is necessary to remove the entire tract and check it closely, particularly in the convoulted area.

Tried to test the EGR valve by putting a vacuum on the valve - couldn't get to more than about 5", but engine stumbled a bit, so I'm assuming EGR is functional.

At least the valve is good and not clogged. Still no idea of how each port is flowing though.

Interested that I couldn't get a decent vacuum, I did some close listening (at idle), and I heard what sounds like an air leak.

Were you using a vacuum gauge? How much vacuum do you have @ idle? Try using flammable carb cleaner, spraying near hoses and mechanical joints to find leaks.

Took the top black pieces off the intake manifold and it definitely sounds like an air leak somewhere under the manifold - loudest when I put my ear near the opening where the PCV valve is located.

I wish I could remember what it should sound like....So, my question - is this air leak sound normal, or do I need to pull the manifold & replace hoses, etc.?
I hear ya buddy. It's especially difficult to differentiate the noise that is normal from a bonafide leak. You should try listening to newer engines with plastic manifolds! My experience is that going by sound alone is a sucker bet anymore. Use the carb cleaner.
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  #28  
Old 04-14-2005, 07:10 PM
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the cleaner is the best idea
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  #29  
Old 04-14-2005, 07:48 PM
lee lee is offline
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Beav,

I'm showing a very steady value of about 18" vacuum at idle (using port on passenger side, rear of intake), but I have no idea how accurate my gauge is - I'm using a cheap MityVac vacuum pump originally bought for brake bleeding - can't find my old vac gauge. That's what I was using to test the EGR - I am under the impression that pulling around 10" would almost kill the engine, but I couldn't get there.

My Alldata CD says I should be getting around 20.08 minimum, which given the steady reading, and the sound of air leaking - that's why I asked what I did.

This weekend I'll take off the whole plastic air intake tract & give it a once over.
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  #30  
Old 04-26-2005, 02:43 PM
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UPDATE:

I changed out the Bosch platinum +4 plugs (25k Miles - shame on them) for Denso Iridium, found and plugged not 1, not 2, but three holes in the intake tube...time to start looking for a replacement I guess.

Drivability is now much better. Still have an occasional miss at idle (like dropping a cylinder every 3-5 seconds at idle). Light to mid- throttle is fine now...haven't really tried WOT. Maybe need to do some throttle body cleaning, also probably time to change out the PCV valve.

Two things I'm still worried about (any help, especially on #2 would be welcome):

1) the sound of air around the intake - the hose from the intake to the regulator for the purge canister is VERY hard & brittle, could be a leak under there - maybe some day I'll pull the whole thing & replace hoses - for now a spray of carb cleaner to the places I can do with with it all together do not yield any results, i.e., no stumbling like the cleaner is being sucked up - but the again I can't see the end of the hose for the purge canister either, so....

2) Alldata says the EGR should hold 8" of vacuum and cause the engine to stumble - I can apply vacuum and get the stumble, but it won't hold it, I have to keep pumping to see any effect.
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