Rough idle
08-31-2010, 04:39 PM
#1
Instructor
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Location: Lake Elsinore, California
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Rough idle
Ok, the car is an 88S4 auto and it sat for about a year after it developed a wild idle (RPMs would swing from almost stalling to ~4KRPM) I park the car and removed the intake to have a look underneath. It took some time to get back into working on the car and in the end, changed out the MAF, fuel injector orings, and all the vacuum lines. I started her up the other day and the RPM idle problem is gone. However, the problem now is not all the fuel injectors are energizing. I placed a mechanic's sthethoscope to each injector and I can hear the ticking on some but not others. Any suggestions?
Thanks in advance
Thanks in advance
08-31-2010, 06:17 PM
#2
Drifting
If some of your injectors weren't firing, then your idle problem would still be there. Keep in mind, the 928 injectors are batch fired (they all fire at the same time.)
1. You could be making a mistake in your assessment that they are not all firing.
2. You could have a few bad injectors (possible, but I'm skeptical.)
3. There could be a few broken wires in your injector harness (possible, but not likely, most of the wires in the 928 are pretty high quality and don't randomly break unless you do something really stupid.)
If the idle problem is gone, why do you suspect there is a problem with the injectors? Does it idle at the correct speed, but stumble, cough, etc? Have you driven it since you did this work?
If some of the injectors are not firing as you hypothesize, but your idle speed is correct, then the reason it is probably correct is due to fuel starvation, and once the fuel starvation is corrected, you could find your idle back up to where it was.
Have you considered that the problem is ignition related? Did you at least rule out placing a plug wire on the wrong plug?
How many injectors do you think are not firing? Do those that are not firing feed cylinders that all correspond with the same coil and distributor cap?
1. You could be making a mistake in your assessment that they are not all firing.
2. You could have a few bad injectors (possible, but I'm skeptical.)
3. There could be a few broken wires in your injector harness (possible, but not likely, most of the wires in the 928 are pretty high quality and don't randomly break unless you do something really stupid.)
If the idle problem is gone, why do you suspect there is a problem with the injectors? Does it idle at the correct speed, but stumble, cough, etc? Have you driven it since you did this work?
If some of the injectors are not firing as you hypothesize, but your idle speed is correct, then the reason it is probably correct is due to fuel starvation, and once the fuel starvation is corrected, you could find your idle back up to where it was.
Have you considered that the problem is ignition related? Did you at least rule out placing a plug wire on the wrong plug?
How many injectors do you think are not firing? Do those that are not firing feed cylinders that all correspond with the same coil and distributor cap?
09-02-2010, 10:44 PM
#4
Team Owner
what was the last thing you fixed before the idle went crazy?? i would also check the throttle cable to make sure that it is fully released and that the throttle position switch is in fact fully released and you can hear it click when the throttle is released
