S4 power loss - HELP
07-05-2004, 10:00 PM
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S4 power loss - HELP
After a lot of pushing from me... I at last managed to talk my brother into buying a 1988 928 S4 and he has had the car for almost a year now.
At first it ran great. But over the last 4000 miles, the power seemed to have slowley bled off until we are at where we are now, where my 2.5 944 would probably wipe the floor with it, which just isnt right!!!
I suspect that his engine mounts are on the way out, so its hard to tell if it also has a misfire or not... it feels quite out of balance above idle speed.. at idle speed you can feel some vibration, but not alot.. but if you sit there and rev her up, she feels a little nasty.. almost like something out of balance... or a misfire, but as I said, this could be the engine mounts on the way out. it seems to feel worst, at about 3000 rpm and up
The power loss is the real issue at the moment.. here is what we have tried.
Distributor caps were in a bit of a mess... we cleaned all the burnt contacts up, wiped out the soot and cleaned up the rotor arms.. tomorow these will be replaced, but for the time being, it seemed to help the engine, but the power is still lost.. So I hope the new caps and arms will improve a little, I dont think its going to be the cure.
Disconnected the MAF, as per the jdsporsche page... it started ok, but it would not rev and stalled as soon as you try to pull away.
Looked inside MAF 4 seconds after shut down (again as per the jdsporsche pages), it looked like a section, about 4 to 6 mm long inside, glowed for a second, but not what I expected... it was quite bright, but I expected to see the whole wire, about 15mm or more to glow.. but it only looked like part of it glowed... but then again, its hard to look down there without putting dents in the wing (fender) tops.
Checked the temp sensor 2... seems to be giving a correct reading on both wires...
It was hard to tell, but I am sure that when my brother drove off, it looked like there was a very tiny amount of black sooty particles from his exhaust.. it was by no means a cloud... but it has got me thinking "rich mixture"... I tested the fuel pressure.. it seemed OK... about 47PSI at idle, when you rev it, for a moment it goes up to the low 50's, then back to 47 PSI,... but it does seem to flutter around by about 5psi in time with the engine, or rather each injector pulse.
Going to put an exhaust probe up its exhaust in the morning and sniff the exhaust... will be able to report back with HC and CO readings... will take measurements from the tailpipe and the test ports next to the air filter... not sure if this one has a cat... an easy way to tell???
I took the car out twice today... both for 15 min runs... at highway speeds it feels smooth, but gutless... if you lift off the throttle and hammer it back down, it goes... but the 944 would still whoop it (which isnt ever right!)
Taking it out around town... it seems almost like one time you will try to make it kick down and it will fly (1 time out of 10)... other times it feels like you are towing a car transporter
plug leads look new.... cam belt and water pump were replaced about 10,000 miles ago...
So.. what does everyone think I should check for him next... I talked him into buying this car, so part of me feels like its my job to make sure it runs right.... besides, we cant have his wife saying "I told you a Porsche wasnt a good car" (GrrrrrRRRrrrrr!!!)
At first it ran great. But over the last 4000 miles, the power seemed to have slowley bled off until we are at where we are now, where my 2.5 944 would probably wipe the floor with it, which just isnt right!!!
I suspect that his engine mounts are on the way out, so its hard to tell if it also has a misfire or not... it feels quite out of balance above idle speed.. at idle speed you can feel some vibration, but not alot.. but if you sit there and rev her up, she feels a little nasty.. almost like something out of balance... or a misfire, but as I said, this could be the engine mounts on the way out. it seems to feel worst, at about 3000 rpm and up
The power loss is the real issue at the moment.. here is what we have tried.
Distributor caps were in a bit of a mess... we cleaned all the burnt contacts up, wiped out the soot and cleaned up the rotor arms.. tomorow these will be replaced, but for the time being, it seemed to help the engine, but the power is still lost.. So I hope the new caps and arms will improve a little, I dont think its going to be the cure.
Disconnected the MAF, as per the jdsporsche page... it started ok, but it would not rev and stalled as soon as you try to pull away.
Looked inside MAF 4 seconds after shut down (again as per the jdsporsche pages), it looked like a section, about 4 to 6 mm long inside, glowed for a second, but not what I expected... it was quite bright, but I expected to see the whole wire, about 15mm or more to glow.. but it only looked like part of it glowed... but then again, its hard to look down there without putting dents in the wing (fender) tops.
Checked the temp sensor 2... seems to be giving a correct reading on both wires...
It was hard to tell, but I am sure that when my brother drove off, it looked like there was a very tiny amount of black sooty particles from his exhaust.. it was by no means a cloud... but it has got me thinking "rich mixture"... I tested the fuel pressure.. it seemed OK... about 47PSI at idle, when you rev it, for a moment it goes up to the low 50's, then back to 47 PSI,... but it does seem to flutter around by about 5psi in time with the engine, or rather each injector pulse.
Going to put an exhaust probe up its exhaust in the morning and sniff the exhaust... will be able to report back with HC and CO readings... will take measurements from the tailpipe and the test ports next to the air filter... not sure if this one has a cat... an easy way to tell???
I took the car out twice today... both for 15 min runs... at highway speeds it feels smooth, but gutless... if you lift off the throttle and hammer it back down, it goes... but the 944 would still whoop it (which isnt ever right!)
Taking it out around town... it seems almost like one time you will try to make it kick down and it will fly (1 time out of 10)... other times it feels like you are towing a car transporter
plug leads look new.... cam belt and water pump were replaced about 10,000 miles ago...
So.. what does everyone think I should check for him next... I talked him into buying this car, so part of me feels like its my job to make sure it runs right.... besides, we cant have his wife saying "I told you a Porsche wasnt a good car" (GrrrrrRRRrrrrr!!!)
07-05-2004, 10:29 PM
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Have you read Worf's debacle?
https://rennlist.com/forums/showthre...hreadid=126435
Find his follow up thread for the resolution of the problem!
https://rennlist.com/forums/showthre...hreadid=126435
Find his follow up thread for the resolution of the problem!
07-05-2004, 11:11 PM
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Originally posted by Old & New
Have you read Worf's debacle?
Have you read Worf's debacle?
I was thinking the same thing. That poor f#&#er Worf...
But, it does sound somewhat the same. Except that the '89 ran smooth as silk. But no guts.
And even if it isn't the same problem that thread has all the possible culprits.
07-05-2004, 11:12 PM
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Originally posted by Old & New
Find his follow up thread for the resolution of the problem!
Find his follow up thread for the resolution of the problem!
But, you reminded me that I should post the follow-up follow-up from the Dyno run. Stand by (in the other thread...)
07-06-2004, 03:16 AM
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Leaky fuel dampers?
Vac leak?
Pull the plugs and see what kind of shape they are in?
If you have a buddy with a loaner, swap out the "big ticket" items like the LH, and MAF. that way you can eliminate them
let us know what you find
Vac leak?
Pull the plugs and see what kind of shape they are in?
If you have a buddy with a loaner, swap out the "big ticket" items like the LH, and MAF. that way you can eliminate them
let us know what you find
07-06-2004, 05:47 AM
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Hi Renn,
It sounds as though the MAF is badly aged, the car is a non cat model, they are more sensitive to MAF ageing. An aged MAF will cause weak running andf poor power in the mid range. When you hit WOT, the mixture is richened a bit, and the car gets a bit more lively.
I can check the MAF calbration for 20GBP. Contact me at my website e-mail
How many miles on the car ?
It sounds as though the MAF is badly aged, the car is a non cat model, they are more sensitive to MAF ageing. An aged MAF will cause weak running andf poor power in the mid range. When you hit WOT, the mixture is richened a bit, and the car gets a bit more lively.
I can check the MAF calbration for 20GBP. Contact me at my website e-mail
How many miles on the car ?
07-06-2004, 06:23 AM
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Just dropped the car off with my local Porsche specialist, Jon Mitchell here in Bournemouth, as I think I am out of my depth on this.
His first reaction was to check the ignition side, he has said that both rotor arms and distributor caps are a mess and need to be renued. However he said that this is unlikely the cause of the power loss.
His bet is the MAF, Hall effect, Knock sensors.. he is going to check the knock sensors first, then work through things.
I have told him to get in touch with you John. So expect an email.
The car has only done about 50k... everything seems tip top except the power issue and perhaps the engine mounts.
His first reaction was to check the ignition side, he has said that both rotor arms and distributor caps are a mess and need to be renued. However he said that this is unlikely the cause of the power loss.
His bet is the MAF, Hall effect, Knock sensors.. he is going to check the knock sensors first, then work through things.
I have told him to get in touch with you John. So expect an email.
The car has only done about 50k... everything seems tip top except the power issue and perhaps the engine mounts.
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07-06-2004, 07:11 AM
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One other thing I would have looked at are the ignition wires (open hood at night and check for fireworks), as well as the connectors at the coils. Why? Because you wrote that it's worse at higher rpm - coils might be able to keep up at low rpm, but not at high revs.
Best of luck! Let us know what you find!
Best of luck! Let us know what you find!
07-06-2004, 07:53 AM
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I second Johns opinion... Your description of symptoms and the things you've tried sounds exactly like my 87 a year ago. After receiving a fresh MAF from John it felt like I had a brand new car.
Have the MAF checked first. It's easy and it's cheap.
Have the MAF checked first. It's easy and it's cheap.
07-06-2004, 11:10 AM
#10
Racer
Check this thread we just covered the same subject
I think this thread is just about exhaustive on the subject. I wish you the best of luck on this potentially expensive journey
https://rennlist.com/forums/showthre...hreadid=142351
https://rennlist.com/forums/showthre...hreadid=142351
07-07-2004, 02:19 PM
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I had a similar loss of power issue with my '87 S4. First I changed the MAF, that didn't do anything. Rotors and caps were new so nothing needed here. Then I changed the plugs, ingition wires and coils and voila, I have never looked back. I am betting on the ignition. Also check thoroughly for vacuum leaks.
07-07-2004, 03:18 PM
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Had the report from my local guy Jon Mitchell.. he reported that the distributor caps and arms are past their best and that the MAF was suspect.
Its going back in a few days to have the distributor caps and rotor arms changed (they need doing) and see how it runs then.
Once thats done he can do some more digging including checking the coils. But he said once we know everything else is A-OK, then its going to have to be the MAF which will be sent off to JDSPorsche to be fixed... ho hum, I have a feeling its going to be expensive!
Its going back in a few days to have the distributor caps and rotor arms changed (they need doing) and see how it runs then.
Once thats done he can do some more digging including checking the coils. But he said once we know everything else is A-OK, then its going to have to be the MAF which will be sent off to JDSPorsche to be fixed... ho hum, I have a feeling its going to be expensive!
