My car is a 96' with a TD04 DIY turbo. It was tuned by Granite State Dyno. Basically, the symptom is that after driving on the highway for a while, and the car comes to temperature, the car will not idle well at stoplights or red-lights. It will hunt between 500-1200 rpm, and not as a result of fans kicking on. In other words, I'll come to a red light, the engine will hunt between 500-1200, and if the fan kicks on, at 500, the engine will just die. This seems to occur on hot days (80+) as well as moderate days (60).

Possible issues:
IAT heat soak? I have not logged coming to a red light yet, but i don't recall the wide-band registering very high AFR for example. How else can I test?

What other issues might this symptom describe?

 

you need more fuel.


what ecu?

 

Thanks Brain, it is an MSPNP2, I forget if tuned for batch or sequential at this point. The fuel system is made up of flow-force, something larger than 750, with an mtuned rail and aeromotive regulator. The motor trackspeed and fuel system from Leafy a few years ago.

Should I just set a 5% lower AFR target in the fuel map between 500-1100 rpm, and then autotune? The strange thing is that this tends to only happen when hot, and idles well on initial startup.

 

what's your MAT corrections table look like?

tl;dr that's your problem, zero it out to 100% flat and tune it accordingly.

 

Awesome thanks, I'll look into that.

It's in a realm beyond my full understanding and that's why I had the tuner work on it and kept the file unmolested after, but then here we are.

Under boost on track the car is great, wouldn't MAT adjustment affect the car's behavior globally?

 

tuners never actually tune the car to run well on the street, just to make power on a dyno.

 

Yes, that's the impression I got. Thanks Brain. How can I tune MAT with affecting the global tune?

 

its a multiplier on your fuel algorithm, and I'm betting currently it's set to reduce you fuel almost 20% when the AITs increase.

 

This, so much this.