Help Please 1989 S4 stops running like it got hot, but temp is good
07-22-2012, 10:01 AM
#16
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One more thing: have you done anything to/with the water bridge (when you worked the intake over?)
07-22-2012, 10:03 AM
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IMS is standard equipment starting in '89.
Also, search for Diagnostic Port, Bosch Hammer, and Theo Tool.
07-22-2012, 10:15 AM
#18
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The ignition Monitoring System shuts down half the engine, not all of it. I don't remember ever hearing of that system stopping the engine completely.
The late 928 has two virtually independent ignition systems, so the problem is not at all likely to be a coil, ignition amp, etc.
The injection system is likewise controlled in the same two four-cylinder groups, which is what the Ignition Monitoring System shuts off when the exhaust temps get uneven.
Single point failure possibilities include the ignition switch, any of the three critical relays, and the Crank Position Sensor.
The late 928 has two virtually independent ignition systems, so the problem is not at all likely to be a coil, ignition amp, etc.
The injection system is likewise controlled in the same two four-cylinder groups, which is what the Ignition Monitoring System shuts off when the exhaust temps get uneven.
Single point failure possibilities include the ignition switch, any of the three critical relays, and the Crank Position Sensor.
07-22-2012, 10:36 AM
#19
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First remove the airbox and MAS.
Apply a vacuum hand pump at the vacuum port to your two fuel dampeners and fuel pressure regulator. They should hold vacuum. If they do not, then that will be part of the problem as fuel will be sucked into the intake through the vacuum lines. Also, if they do not hold vacuum, your hand pump will be full of fuel and so will all of the vacuum lines from the 5-way connector and you'll need to replace all the vacuum lines and rubber elbows connected to the 5-way or be sorry later.
Under the FPR and rear dampener, check that the two LH ground points are connected, clean, and tight. A bad or loose LH ground will cause the problem you describe.
Never mind - you DID replace the CPS. Last, when you did the intake refresh you should have changed the CPS. It's a know time-related failure point.
Really last, an intake leak at the throttle shaft bearings cannot cause the symptoms you describe if everything else is right. Worst case a leak at the bearings might contribute to a slightly-high idle.
Apply a vacuum hand pump at the vacuum port to your two fuel dampeners and fuel pressure regulator. They should hold vacuum. If they do not, then that will be part of the problem as fuel will be sucked into the intake through the vacuum lines. Also, if they do not hold vacuum, your hand pump will be full of fuel and so will all of the vacuum lines from the 5-way connector and you'll need to replace all the vacuum lines and rubber elbows connected to the 5-way or be sorry later.
Under the FPR and rear dampener, check that the two LH ground points are connected, clean, and tight. A bad or loose LH ground will cause the problem you describe.
Never mind - you DID replace the CPS. Last, when you did the intake refresh you should have changed the CPS. It's a know time-related failure point.
Really last, an intake leak at the throttle shaft bearings cannot cause the symptoms you describe if everything else is right. Worst case a leak at the bearings might contribute to a slightly-high idle.
Groovy. Will do. It does not seem that the issue is related, but now I can go back and reread....
07-22-2012, 10:38 AM
#20
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The ignition Monitoring System shuts down half the engine, not all of it. I don't remember ever hearing of that system stopping the engine completely.
The late 928 has two virtually independent ignition systems, so the problem is not at all likely to be a coil, ignition amp, etc.
The injection system is likewise controlled in the same two four-cylinder groups, which is what the Ignition Monitoring System shuts off when the exhaust temps get uneven.
Single point failure possibilities include the ignition switch, any of the three critical relays, and the Crank Position Sensor.
The late 928 has two virtually independent ignition systems, so the problem is not at all likely to be a coil, ignition amp, etc.
The injection system is likewise controlled in the same two four-cylinder groups, which is what the Ignition Monitoring System shuts off when the exhaust temps get uneven.
Single point failure possibilities include the ignition switch, any of the three critical relays, and the Crank Position Sensor.
The CPS is new, which does not mean it could not be the problem, but let me get her back on the road with the relays first... then call roger for a spare CPS if I am still shutting down...
07-22-2012, 02:28 PM
#21
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OK, all back together and running the best it ever has... all that front end power you expect 
whoo-hooo... The lag and the delays are all gone (so far this AM)...
I need to drive it a while to check if it dies off again...
Thanks for the help so far and will let you know as soon as I know....
whoo-hooo... The lag and the delays are all gone (so far this AM)... I need to drive it a while to check if it dies off again...
Thanks for the help so far and will let you know as soon as I know....
07-22-2012, 04:21 PM
#22
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Well, 30ish min into the trek and same problem. I played with RPMs and as it got close to the shut down time it was acting like the rev limiter was kicking it at about 4000 RPMs. Dies, 5 min later I was able to crak her upo and pull into a parking lot.
Relays are all changed, no vac leaks, now I am looking for something new.
I do get spark because I can crank it right back up, it just won't run.
Any other ideas?
Relays are all changed, no vac leaks, now I am looking for something new.
I do get spark because I can crank it right back up, it just won't run.
Any other ideas?
07-22-2012, 04:36 PM
#23
How old is the fuel pump/filter?
07-22-2012, 07:07 PM
#24
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We had a MAF that was diagnosed as having a circuit that would fail when hot and shut it down. (Rich Andrade found it). Its one possibility. Can you swap MAF's?
Also, had some sort of harness issue on the 85 that I think was a bad connection inside the harness. Would happen intermittently. This was the rear engine harness that collects-up the CPS and MAF and other important ground wires at the back of the valley.
Just a couple of ideas.
Oh, one more. Equally obscure and more speculative. A few of the replacement CPS that I've seen lately have seemed less well-made. On trying to turn them a bit to align the retaining screw the metal barrel was stationary, but the plastic body started to turn. (The old ones being replaced seemed fused to together better). Anyway, it wouldn't be that expensive to replace the CPS again and try it. I too have experienced intermittent CPS failure and have a shop owner friend who also has seen them fail hot.
Also, had some sort of harness issue on the 85 that I think was a bad connection inside the harness. Would happen intermittently. This was the rear engine harness that collects-up the CPS and MAF and other important ground wires at the back of the valley.
Just a couple of ideas.
Oh, one more. Equally obscure and more speculative. A few of the replacement CPS that I've seen lately have seemed less well-made. On trying to turn them a bit to align the retaining screw the metal barrel was stationary, but the plastic body started to turn. (The old ones being replaced seemed fused to together better). Anyway, it wouldn't be that expensive to replace the CPS again and try it. I too have experienced intermittent CPS failure and have a shop owner friend who also has seen them fail hot.
Last edited by Landseer; 07-22-2012 at 07:32 PM.
07-22-2012, 07:44 PM
#25
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All new. 044 pump and in tank removal.
I am lucky enough to have two 89s, so I will try that next.
Question, the MAF is the entire tube and sensor correct? I have discovered that is will not hold pressure. The sensor "lid" leaks when under pressure... Let me swap that and try that next...
I will have roger send me another CPS as well... Wish that puppy was easier to get to...
We had a MAF that was diagnosed as having a circuit that would fail when hot and shut it down. (Rich Andrade found it). Its one possibility. Can you swap MAF's?
Also, had some sort of harness issue on the 85 that I think was a bad connection inside the harness. Would happen intermittently. This was the rear engine harness that collects-up the CPS and MAF and other important ground wires at the back of the valley.
Just a couple of ideas.
Oh, one more. Equally obscure and more speculative. A few of the replacement CPS that I've seen lately have seemed less well-made. On trying to turn them a bit to align the retaining screw the metal barrel was stationary, but the plastic body started to turn. (The old ones being replaced seemed fused to together better). Anyway, it wouldn't be that expensive to replace the CPS again and try it. I too have experienced intermittent CPS failure and have a shop owner friend who also has seen them fail hot.
Also, had some sort of harness issue on the 85 that I think was a bad connection inside the harness. Would happen intermittently. This was the rear engine harness that collects-up the CPS and MAF and other important ground wires at the back of the valley.
Just a couple of ideas.
Oh, one more. Equally obscure and more speculative. A few of the replacement CPS that I've seen lately have seemed less well-made. On trying to turn them a bit to align the retaining screw the metal barrel was stationary, but the plastic body started to turn. (The old ones being replaced seemed fused to together better). Anyway, it wouldn't be that expensive to replace the CPS again and try it. I too have experienced intermittent CPS failure and have a shop owner friend who also has seen them fail hot.
Question, the MAF is the entire tube and sensor correct? I have discovered that is will not hold pressure. The sensor "lid" leaks when under pressure... Let me swap that and try that next...
I will have roger send me another CPS as well... Wish that puppy was easier to get to...
07-22-2012, 09:27 PM
#26
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Test the Temp II sensor body when hot and make sure that it has a good connection to engine ground. Powder coating can insulate the sensor or cross-over from ground.
07-22-2012, 09:31 PM
#27
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07-23-2012, 01:04 PM
#28
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Another data point... drvoe the car home last night in the cool rainy weather (monsoon season here) for about an hour and not an issue (though I did not ride her hard)...
Definitly a temperature driven issue that is eitehr changing the resistance of a faulty sensor (MAF, T2, CPS, tbd) or possible fuel related (but this seems more unlikely because it is not getting hot enough to cas fuel flow issues)....
Thanks again for alll the help so far and the help yet to come!
Emerald
Definitly a temperature driven issue that is eitehr changing the resistance of a faulty sensor (MAF, T2, CPS, tbd) or possible fuel related (but this seems more unlikely because it is not getting hot enough to cas fuel flow issues)....
Thanks again for alll the help so far and the help yet to come!
Emerald
07-23-2012, 03:29 PM
#30
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It does with or without the AC on. I have insullation (had I pulled it off) on the fuel rails, but the engine is not getting very hot. I also think that if it was hot, I would have possible more issues at lower RPM than high... at high I am moving more fuel so its thermal soak would be lower... at least the way I am thinking about it...