capnbob928s4

Thanks for reading. I have a '88 928s4, 5speed. Replaced the LH computer two weeks ago with a rebuilt one from 928 International. The injector noise stopped and the car started and ran well for two days. Parked it for a week and now it runs awful. Starts right up but then settles into a sporadic idle and won't rev normally either. Hold the pedal at 2000 RPM and it will stay there for a few seconds then wander all over the place. Tried driving it and it bucked and hesitated. Occasionally, it would accelerate normally. Ordered a new mass air flow sensor which should be here tomorrow. Unplugged the old one and the car would start but only run for a few seconds. I was told that the car should run at idle with the mass air flow sensor unplugged but this one won't. Plugged it back in and the car started and ran but the idle was still hunting. Is this a problem with the LH computer? Any other ideas? I really appreciate your assistance. Thank you.

Robert

John Speake

Hello Robert,
Difficult to diagnose...problem could be LH but could be other, such as O2 sensor problem. See what the new MAF does, if no better let us know and we will try and help you through this isse

Bill Ball

Rather than buying parts, it would be good to find another 87-91 S4/GT in your area that would be willing to serve as a test bed. We do this locally all the time to troubleshoot issues like this. Take your suspected LH or MAF and install it in the test bed and see if it malfunctions similarly. So, provide your location in a request for help if the new MAF does not fix this.