Does the TPS control Fuel, or does it control Spark when you step on the gas...or both? I am having a HUGE problem with my engine cutting out and missing when I give the car gas. I am 90% sure it is a spark problem because my O2's read SUPER rich immediately after it cuts out, which tells me it is getting fuel but not burning it. I unplugged the TPS and plugged it back in and it seemed to improve the situation SLIGHTLY, but did not solve it...PLUS, on my datalogs, the TPS seems to be reading correctly...could it still be bad but be reading right on my datalogs?

 

Not burning fuel reads as LEAN on O2s because the OXYGEN they read wasn't consumed in burning fuel.

I would hook up the scanner and slowly depress the throttle with the key on not running and watch the scanner for smooth and appropriate response. If you get that then the TPS is fine.


Is this a immediate problem with the new build?
Is it a sudden problem on a previously good running combo?
Any work done on the car right before this presented?
Both side O2s react the same?

 

This is a problem that occurred well after the build was done...I dynoed 442, it was running great, broke a torque are and shredded a carrier...Soon after I destroyed the carrier, this began, but it continued even after fixing it. It was sudden and came out of nowhere.

It idles rough on a cold startup, but once it reaches operating temps it smooths out. At idle, I can go WOT and it cuts out and stutters for a couple of seconds, then it will rev. While driving, anywhere under 3000 rpms, if I go WOT it reacts the same way. If I use light acceleration under 3K, it will accelerate but it is not as smooth as it should be. Over 3K, I can go WOT and it doesnt stutter and it accelerates strong, but it is not full power. If I drive it cold with light throttle, it will fight me between idle and 1500 rpms, then smooth out to around 2800-3000, then it seems like it just doesnt want to accelerate anymore...like I hit a wall and the more throttle I give it to try and pick up speed (mainly on the on-ramp of the interstate headed to work), it stutters and spits...I have not tried to push it through that yet, I just shift and use the lower RPMs until I get up to speed.

It ran MULTIPLE 400+ dyno runs before this, and had gone WELL over 1000 miles to include city and highway driving and road trips over 100 miles and I had no issues. I was tuning it and trying to solve my split BLM problem...I did some modification to the throttle body and tweaked the tune some more. Immediately after that I did a WOT run and it was VERY strong...so strong that it broke the rear end. I fried a PCM in the process of tuning at one point and I installed another one until I got my new chips in from Madtuner. I thought maybe it was the new PCM, so I installed the chips and put the old PCM back in, but no chance. I reverted to older tunes to include the identical tune of the 442 dyno run, and no change.

ALSO, the car is running in Speed Density Mode, activated through the PCM. I was tuning it this way because if I use MAF mode, the car will not run at ALL. IT will fire and run with throttle, but if I let off of the gas, it dies instantly, and not a stutter die, but an immediate halt. I figured MAF tables are off, or MAF is bad so I switched back to SD mode and it ran great...not sure if this is linked or not.

Also yes, both O2's react the same way.

 

sorry to say it but have to double checked your wires for burns...

 

yes, I have them routed over the valve covers. None of them are touching the headers at all, and they don't go anywhere else where they can burn through...I inspected them to make sure, but they are in good shame and nothing is arcing.

 

If it goes super rich only a few things can be happening, 1 either the fuel isnt being burned (problem with spark) or it commands a bunch of extra fuel...

Out of curiosity, what is your IAT sensor reading?

 

I will have to look again, but at the time read around 85-90 degrees. Engine was warm but not up to operating temp and it was maybe around 55 degrees outside.

It could be commanding more fuel but how do I check that? I know my fuel pressure doesnt seem higher than usual and the trims are still split pretty bad.