My car is possessed (video)
06-27-09, 01:58 PM
#1
My car is possessed (video)
It seems once the weather got real hot and humid here in Iowa it started to run like this and the clock started turning on and off. So far I have changed the spark plugs and the thermostat, adjusted the tps, cleaned the bac valve and I can't find any vacuum leaks. The car is a 88 s4 na no mods
Video is of a warm start. On cold starts it idles alright until it is warm, then this happens
Video is of a warm start. On cold starts it idles alright until it is warm, then this happens
06-27-09, 02:20 PM
#2
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Exorcism? 
100% sure the BAC is working properly? What about your cold start thing? It is attached to the throttle body, has coolant running around it. Maybe it is failing? Just throwing ideas out there.
My first thought was BAC. But if that is fine.... How is it when you drive? Pull strong, etc?
100% sure the BAC is working properly? What about your cold start thing? It is attached to the throttle body, has coolant running around it. Maybe it is failing? Just throwing ideas out there.
My first thought was BAC.
But if that is fine.... How is it when you drive? Pull strong, etc?
06-27-09, 06:33 PM
#4
The clocks ALWAYS fail. If it's worked this long, consider yourself lucky. The solder joints to the board are notoriously cold. It's not related to your idle problem.
For the idle, have you tested the resistance values on the TPS, or just set it by voltage or the two-light method? Are they within spec, and are there any dead spots in the sweep? (http://howto.globalvicinity.com/gv_w...i=58&co=1&vi=1) It's clear the ECU is correcting for whatever the problem is, which is what's causing the idle speed to jump around. I'll bet if you unplug the BAC, while it's idling, it'll probably stall. The changes are random enough that I'd say a vacuum leak is not too likely; I've always gotten a rhythmic bounce in idle speed with big leaks. If not the TPS, the BAC or maybe even the AWS solenoid may be getting triggered when they're not supposed to. See if you can eliminate things by unplugging, then checking the result.
For the idle, have you tested the resistance values on the TPS, or just set it by voltage or the two-light method? Are they within spec, and are there any dead spots in the sweep? (http://howto.globalvicinity.com/gv_w...i=58&co=1&vi=1) It's clear the ECU is correcting for whatever the problem is, which is what's causing the idle speed to jump around. I'll bet if you unplug the BAC, while it's idling, it'll probably stall. The changes are random enough that I'd say a vacuum leak is not too likely; I've always gotten a rhythmic bounce in idle speed with big leaks. If not the TPS, the BAC or maybe even the AWS solenoid may be getting triggered when they're not supposed to. See if you can eliminate things by unplugging, then checking the result.
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06-29-09, 09:29 PM
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06-29-09, 09:55 PM
#13
I have the same problem right now but mine jumps a little more. Going to clean the BAC valve tomorrow. Curious tho, you said it idles alright till its warm. Mine is like the opposite, lumpy idle still its fully warm. Then its pretty steady. Cleaning the BAC valve should fix this? Im pretty sure i have my TPS adjusted correctly and im certain i have no vac leaks. - Nick
EDIT: From the link you posted my TPS maybe bad.
EDIT: From the link you posted my TPS maybe bad.
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