Idle issue
11-13-2013, 01:40 AM
#16
Track Day
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Join Date: Apr 2011
Location: Perth
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Does this car have an O2-sensor? Or was it Euro spec with no cats and no O2-sensor?
This sounds exactly like a messed-up (aging or dead) narrow-band O2-sensor. When the coolant temp reached 50-60C then the LH starts adjusting fuel based on the o2-sensor reading. If the O2-sensor is providing bad info then the LH takes that bad info and does stupid things with fueling, as soon as the coolant reaches the magic temperature.
So if you have an O2-sensor (on top of the crossover just ahead of the cats) then try a new one. They typically last around 100km's, plus/minus.
Cheers, Jim
This sounds exactly like a messed-up (aging or dead) narrow-band O2-sensor. When the coolant temp reached 50-60C then the LH starts adjusting fuel based on the o2-sensor reading. If the O2-sensor is providing bad info then the LH takes that bad info and does stupid things with fueling, as soon as the coolant reaches the magic temperature.
So if you have an O2-sensor (on top of the crossover just ahead of the cats) then try a new one. They typically last around 100km's, plus/minus.
Cheers, Jim
It's a UK car, no cats or 02
Cheers
11-13-2013, 02:17 AM
#17
+1 to JDS post.
My car is the same, no cats and no O2 sensor however it is a 1990 S4 auto fitted with a digital dash and I can check the operation of the throttle switch indicating shut and open. I can also activate the ISV via my Diagnostic Tester DT928 and listen to it spring shut after the opening signal.
If you have a Test Procedure Manual for the MY 1987 and you are a competent DIYer you can activate these items via manual input signals.
However, I would also check the settings on the Bowden cables to the throttle connections, such as throttle settings, shut throttle at idle (to ensure that ISV is controlling the idle rpms and wide open throttle and cruise control . These are set with the engine off. Refer to the WSM or do a "search" function here.
Give the ISV a good squirt down the pipe connection. I usually use a flexible plastic straw to get the WD40 down a close to the ISV as possible to remove the oil debris inside the ISV and I do this at each service.
My car is the same, no cats and no O2 sensor however it is a 1990 S4 auto fitted with a digital dash and I can check the operation of the throttle switch indicating shut and open. I can also activate the ISV via my Diagnostic Tester DT928 and listen to it spring shut after the opening signal.
If you have a Test Procedure Manual for the MY 1987 and you are a competent DIYer you can activate these items via manual input signals.
However, I would also check the settings on the Bowden cables to the throttle connections, such as throttle settings, shut throttle at idle (to ensure that ISV is controlling the idle rpms and wide open throttle and cruise control . These are set with the engine off. Refer to the WSM or do a "search" function here.
Give the ISV a good squirt down the pipe connection. I usually use a flexible plastic straw to get the WD40 down a close to the ISV as possible to remove the oil debris inside the ISV and I do this at each service.