Hey honda-tech, its been a minute! I return seeking help with a problem I just can't seem to resolve.
At low speed/ low throttle the car bucks as if all power is cut and then suddenly comes back up. In neutral, I cannot hold the throttle at 1,500 RPM steady. It will rev and then drop off again. This happens with or without the IACV plugged in. I have checked over the ECU, IACV, TPS, wiring, grounds, etc. I'm just stuck and not sure where to go from here diagnosis wise. When I am driving in traffic or very low speeds, it just sucks to drive. Under heavy throttle/ load there is no issues and the car runs fine. It has been to a local tuner and he thought the issue was the TPS. But that has now been replaced and recalibrated with no change to the issue. I am hoping that there is someone in the DFW area, I am in Rockwall TX, that would be willing to help me diagnose the issue. Please let me know.

Engine is an LSVTEC turbo running on a P28 with S300.

Thanks for any help...

 

Did the tuner check afrs during the situation? Do you have o2 compensation enabled? Check RPMs being logged, distributor triggers could be malfunctioning.

Usually miscalibrated TPS or a bad tune. Throttle tip-in and tip-out might be too rich. Maybe too much timing in the lowest vacuum column. Dropping timing in the lowest column and leaning it out could help. On the flip side maybe it's too lean and needs a little more fuel. Too much timing will make it too sensitive at low speeds/low loads/parking lot conditions.

If it works fine under higher loads could probably rule out a weak spark issue.

 

I will try to get some datalogs from the S300. Maybe it would be helpful to see those. I am not sure exactly what the tuner did to correct the situation. Not sure if he really knew what was going on with it. And not sure about the O2 sensor situation as its just the stock narrow band sensor.