Going very lean at idle/ low throttle
08-18-2012, 11:08 AM
#1
Staging Lane
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Going very lean at idle/ low throttle I am condensing my other posts. I am pulling my hair out with this. Car is a 99 SS a4. has egr, air, cc, and ac removed. LT's, no cats,lid, 150 wet shot, br7 plugs, msd wires. When cold starting it idles great, drives great and a/f is normal (have innovate wideband).As soon as it reaches operating temp the a/f quickly leans out and pegs the meter at 21.9 and runs poor at idle or light throttle. If I give it a decent amount of gas or go wot, it responds, a/f goes normal again and runs great. As soon as I return to light or no throttle the a/f jumps back to pegged lean and runs poor. It had a slp mas and I changed it back to a stock one with no change. I changed the tps and still no different. I've been all over the car to see if there were any vacuum lines open from removing emissions. Found one, plugged it, no change. Ideas?
08-18-2012, 11:17 PM
#6
Sounds electrical to me. You should be able to connect the O2's and meter the voltage on them. You should see fluctuating voltages meaning the O2 is doing its job. Meter from the O2 side as well as the PCM.
I would guess the O2 is shorted to VCC or ground reference is open - causing the computer to think it is running way too rich and leaning out the mixture accordingly. Just a hunch to help in the right direction.
Check Your 12V and Grounds. Check for frayed wiring or loose connections by tugging on wires.
Download the GM F-body 4th gen owners manual - it will have wiring diagrams and color codes.
I would guess the O2 is shorted to VCC or ground reference is open - causing the computer to think it is running way too rich and leaning out the mixture accordingly. Just a hunch to help in the right direction.
Check Your 12V and Grounds. Check for frayed wiring or loose connections by tugging on wires.
Download the GM F-body 4th gen owners manual - it will have wiring diagrams and color codes.
08-19-2012, 02:58 AM
#7
Also worth noting that there are two different types of O2's - case grounded and case open. Not sure which would feed your application but this is another idea to better help solve the problem.
