1990 928 GT with Greg Brown Stroker. Recently Sharktuned with the help of Greg and Jim C. Did some creative work under their guidance. Not sure I'm permitted to share all of it. The idle issue mentioned below began after the Sharktuning efforts mentioned above.

Two idle related issues.

1. Cold startup high idle. Can go and stay at 1500 RPMs. Sometimes it idles at 1200 RPMs. It will stay high well past complete warm up of the engine. This can take up to 1/2 an hour or more of driving before the idle comes down. I've used to the cable quadrant to pull back on the throttle cable to see if the issue is mechanical. No change to idle. I have goosed the engine and sometimes this will help drop the idle lower before or after full warm-up to 1150-1200.

2. Once the idle has settled to the 750ish range the engine continues to hunt for a steady idle. Maybe a swing of 25-50 RPMs.

On my list of things to do is a smoke test.

Looking for some guidance from those steeped in Sharktuning.

I have a couple of logs. But, don't know how to read them.

I should have the Sharktuner back in my hands tomorrow to get more data.

What do I do next?

 

.......So the car doesn't stall and all of this is about a high idle?

Call Jim, once you have the Sharktuner. He will instruct you on how to use your phone as a "hot spot", so he can see the files and how things are set in Sharktuner, in real time.
He's figured out some ways to make the idle a bit happier, using the various parameters.

 

Yes, it's all about the high and hunting idle.
Otherwise, there are no issues that I am aware of related to any of the work you and Kyle did.

 

I had this issue after installing bigger injectors and following the provided guide on adjusting the opening timing for the injectors. I'll have to plug my sharktuner back in to the car to get the specifics, but in the end I had to adjust the injector opening time vis-a-vis the injector size and the warmup enrichment map. Obviously, save your current map and settings before making any changes, but I found that I got the best results if I tuned for a smooth cold and warm-up idle first, and then did the rest of the tuning from there.

You might get lucky and be able to just adjust the warm-up enrichment map. Did you check to see if it's using that while the idle is hunting and then comes off of it when the idle is steady? If so, then you might be able to just adjust that map and leave everything else alone. I would start by checking that.

There is always the possibility that you have a problem with fuel delivery or O2 readings or an air leak. But, since you said it was fine before and all you changed was the programming, I'm assuming that's not the case here. I did chase a bad brand new injector problem for awhile, but all it really did was cause a disparity between the left and right O2 readings. Otherwise it seemed to run ok.

As Greg said, though. If you can get someone to help in real time, that would probably be best.

 

Kevin, tomorrow (Thurs) is good for me if that works for you. We'll want to watch ISV% as it warms up. "Hunting" is not uncommon and usually due to LH tweaking mixture up and down around 14.7. Sharktuner's O2-adjust display is useful here.

Cheers, Jim

 

Please let us know what you find the solution to be

 

I didn't know that Jim can to this

 

Jim and I just completed warm engine shark tuning. The hunting idle is not as severe as it was. Still a bit, but one cannot expect the idle performance to mimic a stock GT with 19# injectors.

Now, I'll take it for a ride and see if the changes had some other unexpected effects. Already idles with AC and fans on and Jim says it looks good.

Thanks Jim C.!

 

What did you change to improve the idle?

 

I had this. It was the wideband o2 sensor / interface....

 

With Sharktuner, once you select the custom idle option, you get to a page with a bunch of potential variables...which the effects are not clearly understood.
Jim knows what these variable do and knows what to set under what conditions.

 

It's not cheap, but worth ever penny....Jim is a genius about this stuff!

 

Truthfully, I've never thought a stock GT to be a "smooth idle" car.

 

So, I was wrong about stalling. My helper drove it with the AC on and it stalled 3 times coming to a stop. Twice in neutral and once in gear.

I'll see about hooking up the shark tuner and logging what is going on this weekend. Stay tuned. (NPI)

 

And believe me I'm getting my money's worth.