Ralph Newman

I have been Sharktuning for the last few days and all was going well. This morning drove to work while logging and got good data and a map I was happy with.
Leaving work I loaded Sharktuner and Sharkplotter for a confirmation run and the car would not return to idle. For instance, I am decelating coming to a stoplight, put the clutch in and the odometer shoots below 675 rpms, immediately dies or or bucks around idle. Made for a long, expletive filled, drive home.
It is crazy. Absolutely nothing changed but the temperature, 40 in the morning and 85 coming home. I tried several other maps I had and really no difference. Help and thanks!!!

jcorenman

Ralph,

Other than the idle, was everything else OK for the drive home? If the fuel is OK then you would expect AFR to be in the mid-14's and O2-adjust to be working normally and staying within +/- 10% or so. Check that while cruising down the road, as well as sitting at idle.

Will the car idle OK just sitting still? What RPM? What does ST show for the ISV% (fuel-monitor page)? When sitting and idling it should be around 50%, plus/minus a few points-- each engine is a bit different.

If you can, post some screen shots of the fuel-monitor page while idling.

Thanks, Jim

Alan

TPS problem? can you confirm idle switch activates?

Alan

Maursy T

Hi Ralph,

Speaking from similar experience I had with my 82 928 s, after spending thousands on engine tuning and fuel injectors with so called experts .. check where your engine ground strap runs and location.
Apparently if located near manifold with increased driving and increase engine temp. you will have poor idle as engine warms up, I replaced mine $40.00 and relocated away from manifold and problem solved.

Hope this may be of some help.

Ralph Newman

Thanks Jim, Alan and Maursy,
Last night, after getting your replies, I go out and start the car. Ran great!! smooth idle, no stumbling. Wow, you guys are good.
Sharktuner showed ISV stable at around 49, and TPS was operating. I was running in open loop but nothing seemed strange about the AFR.
Obviously, I have a transient condition. While waiting for the next episode I am going to lube up my ISV, double check the TPS operation and take a look at my ground.
Thanks again and I will keep you posted, Ralph

Ralph Newman

Further investigation confirms the TPS isn't working correctly. While pushing the gas pedal I watched the TPS change on the Sharktuner's Fuel System Monitor Screen. The TPS would regularly get hung up on cruise and not return to idle. A new one is on order.
The Sharktuner actually made diagnosing this problem fun. Just look at the screen and watch the TPS screw up. Additional kudos for John and Jim.