Suicide!!!
09-12-2011, 11:00 PM
#16
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That's the first place to look.
As Wally suggests, pull the cover off the passenger footwell area and check the ignition monitoring system for a red or green light. My 91 S4 did this intermittently (ran on 4 cylinders) like once every few months, very unpredictable and pretty annoying. The symptoms are exactly what you described - no power, very hard shifting. The right coil is in a cramped area and in my case the coil wire to the distributor became worn by rubbing against a rubber hose that ran near it. I figured it out by first seeing the red light on the relay, knowing it was the right coil, then starting and running the car in a dark garage. The coil wire going to ground was easily seen in the dark, and then replaced the next day. Has run like a top since. Hopefully your problem is that simple.
Check the IMS for the lights and report back.
09-13-2011, 12:28 AM
#17
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Thx.
Ather
09-13-2011, 08:31 AM
#18
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Sod's Law, isn't it?
Took the car for a spin this morning in the hope a miracle had happened overnight. No luck, no power, no joy. Sounded like a steam engine. Still apparently only firing on four.
Had breakfast then returned to check out all the suggestions and advice you guys have given me. Started the engine and it purred like a kitten. Drove it around the block and it performed perfectly. Heavens above!!
Decided anyway to do some of the checks you guys have suggested. First the coil.
The HT lead connection to the coil is badly corroded and there seems to be signs of an electrical arc between contacts.
I don't know whether this is the culprit, but I've ordered a new lead and coil and then I'll keep my fingers crossed.
Took the car for a spin this morning in the hope a miracle had happened overnight. No luck, no power, no joy. Sounded like a steam engine. Still apparently only firing on four.
Had breakfast then returned to check out all the suggestions and advice you guys have given me. Started the engine and it purred like a kitten. Drove it around the block and it performed perfectly. Heavens above!!
Decided anyway to do some of the checks you guys have suggested. First the coil.
The HT lead connection to the coil is badly corroded and there seems to be signs of an electrical arc between contacts.
I don't know whether this is the culprit, but I've ordered a new lead and coil and then I'll keep my fingers crossed.
09-13-2011, 10:11 AM
#19
fonetico, your post (#38) tends to support the view that the ignition monitoring system is activating - when the car is shut down and restarted this system resets itself and all of a sudden the problem disappears until next time. Next time this happens do check the diodes that Wally referred to.
There is a by-pass relay that will bypass this monitoring system, but I reckon that should only be used with extreme caution and understanding.
There is a by-pass relay that will bypass this monitoring system, but I reckon that should only be used with extreme caution and understanding.
09-13-2011, 10:29 AM
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Dave, I'm not entirely sure what I should be looking for.
If I understand Wally correctly, an illuminated diode probably means a fault with the coil or associated wiring.
Or what else should I be looking at?
If I understand Wally correctly, an illuminated diode probably means a fault with the coil or associated wiring.
Or what else should I be looking at?
09-13-2011, 11:11 AM
#21
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A light on the ignition monitoring relay means the car has detected a fault in the ignition system and has shut off fuel to the injectors on the side that has indicated a failure. That's why the engine seems to run on 4 cylinders - it is. Assuming the ignition monitoring is correct, then the problem could be a faulty coil, faulty high tension wire, bad or corroded connection at the coil or distributor, or a bad final stage ignition module. Work through each one. Most likely is bad connection or a bad wire.
09-13-2011, 11:24 AM
#23
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Could one of the ignition amps possibly be giving up? I had similar issues and it turned out to be one of the ignition amps up under the hood on the front bumper on the driver's side of the hood latch. Got a replacement from Roger at 928sRUs over a year ago and no problems since.
09-13-2011, 01:40 PM
#24
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fonetico,
Remove the small carpeted cover from the right kick panel, and put it in the rear floor. Find the clear box at the end of the bracket holding the ECU's.
The next time that the car runs poorly, with the engine still running, look at the box and see if there is a light inside. If the car runs perfectly for several trips, put the cover back on.
The rough shifting is probably because you are using more throttle, since the engine is way down on power. The transmission thinks that you are at full throttle, so it will shift late and hard - as designed.
Remove the small carpeted cover from the right kick panel, and put it in the rear floor. Find the clear box at the end of the bracket holding the ECU's.
The next time that the car runs poorly, with the engine still running, look at the box and see if there is a light inside. If the car runs perfectly for several trips, put the cover back on.
The rough shifting is probably because you are using more throttle, since the engine is way down on power. The transmission thinks that you are at full throttle, so it will shift late and hard - as designed.
09-13-2011, 01:52 PM
#25
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Certainly a corroded coil wire could do this. So, yes, replace it or clean it up. How old are the plug wires? They are a 60K mile replacement item. I'm sure many people stretch that much further, like the 2-year brake fluid flush interval, but that's the recommendation. A full Beru set is quite expensive but should be done periodically if you want the car to run reliably.
I found the coil lead on the passenger side corroded several times, presumably from rain water. Dialectric grease around the lip of the cap to act as a seal may help prevent that.
I found the coil lead on the passenger side corroded several times, presumably from rain water. Dialectric grease around the lip of the cap to act as a seal may help prevent that.
09-13-2011, 01:55 PM
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If the small clip-on trim pieces on the fender lip above the coil are missing, they should be replaced. They are supposed to divert rain and wash water away from the coil and jump start terminal area. Should be found on both fenders...
09-13-2011, 02:06 PM
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Red/port/left and green/starboard/right would make sense?
09-13-2011, 02:23 PM
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Well, they're a couple of interesting comments.
The coil I'm replacing is on the right side. There are definitely no clip-on trim pieces but the coil is concealed below the jump-start terminal. Doesn't this protect it?
The left side coil looks fine but the right side one is badly corroded. Sounds like plug wires might be a good investment in the near future.
Thanks for the info and I know now what to look for if the problem persists.
Important to add that if anything else goes wrong with this infernal machine I'll drive it over a cliff. I will, however, do it with me in it as a concession to the pleasure it frequently gives me.
The coil I'm replacing is on the right side. There are definitely no clip-on trim pieces but the coil is concealed below the jump-start terminal. Doesn't this protect it?
The left side coil looks fine but the right side one is badly corroded. Sounds like plug wires might be a good investment in the near future.
Thanks for the info and I know now what to look for if the problem persists.
Important to add that if anything else goes wrong with this infernal machine I'll drive it over a cliff. I will, however, do it with me in it as a concession to the pleasure it frequently gives me.
09-13-2011, 03:09 PM
#29
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Wally, I'm glad you brought this up. I've seen mention of these seals before, but my car does not appear to have them on either side. When I look at the PET I see a "lateral gasket" on the bonnet (hood) assembly and I'm not sure if that is the part you mean. I have two seals in the area forward of the radiator on the fender lip, but not where the coils are located, and I'm not sure how it would fit around the jump terminal cover on the right side. Anybody have pics of these and/or know which part they are in PET? I see nothing in any of the body sections of PET. I can't recall seeing them on other cars or I just wasn't paying attention. Here's pics of those areas on my car.
09-13-2011, 05:35 PM
#30
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It's a trim piece, (my terminology, not Porsche's), not a seal. It appears that you have the passenger piece - just a little clip-on piece of trim on the edge of the fender to deflect the rain/wash water where it normally spills off onto the coils.