TPS won't reset to 0%
 

Hi every one, I'm having major issues with my car idling, it's a 86 Jaguar xjs with LS1 383 Stroker, comp cam 240/244 113, LS6 heads with bigger valves, dual springs, FAST 102mm throttle body and intake manifold, 65lb injectors, 3000-3200 stall on stock 4L60E, LS7 lifters, comp cam 7.425 push rods, base line tune. Here is what's happening, my TPS will not reset to 0% no matter what we do, every time we get it to read 0%, as soon as i cycle the key and start the car it reads 2.4%-4% every time and the car runs like crap!! My tuner tried tuning it but nothing, we tried resetting the TSP many different ways with no luck whats so ever!! Throttle is not sticking, i have no vacuum leak, TSP voltage is around .65V at idle, fuel pressure is good, no ground issues or connector issues, :bang: only thing i haven't tried is new computer, the TSP has been replaced. I am lost and don't know what to do next, it's my DD and it's annoying to drive!! Any help would be greatly appreciated!

I elongate the TPS holes to adjust the voltage to read different numbers but nothing is working! I've been chasing this problem for couple of weeks now with no positive results!

Are you actually using the TPS reset procedure? Mechanically adjust the TB set screw to desired % with Ignition ON, then turn the Ignition Off and disconnect the TPS connector from the TPS sensor (don't remove the sensor), then turn the Ignition On with the TPS sensor disconnected for a few seconds. Turn it off, reconnect the TPS and clear any TPS DTC's that were set. This should set the TPS to 0-.4%.

With that said, you have a fairly large cam and the 102mm TB which will require some pretty extensive tuning for idle. More than likely you will need to increase the tps % for added airflow because most aftermarket TB's are not preset.

I've tried setting to 0% and then doing the relearn procedure, with the ignition in run position engine off it will read 0% but as soon as i crank the engine it goes back to reading 2.4%-3.1% depends on the voltage setting. The tuner can't really adjust anything until this is fixed, he tried tuning it many different ways but still having that high of a percentage screws everything up. Car won't run right ether, it stalls all the time. How high i can set the TPS %? Thanks for trying to help by the way!!

I will go out and try it the way you told me and see what happens.

Where the voltage is gotta be at?

Does the TPS voltage or % respond to gas pedal input or if you move the TB blade by hand? Are you getting any DTC's?

My voltage is at 0.56v right now and with engine off it reads 0%, as soon as i crank the engine it reads 1.6-2.0% and the car idles at 1400-1650RPM

I'm not getting any DTC when voltage is above 21v and yes it does respond, it will only set the DTC when i unplug the connector!

0.21v

Anybody else wants to help me solve this puzzle please?!?!?!

Find out what is different KOEOff and KOEOn. Measure the 5v reference voltage between the TPS plug and the ground on the battery in both conditions. Measure the voltage between the ground on the tps and the battery ground in both conditions. Measure the tps signal out between the blue tps wire and battery ground in both conditions. Always use the battery - for your ground reference in all measurements. Since this is a trasplant I suspect you may have a grounding issue somewhere.

Ok I'll try that latter on today, the car Is in exhaust shop right now, thanks for the grate info, hopefully it will be grounding issue, I'll let u know as soon as I try it!

Ok everything reads the same at the sensor and at the computer using the battery minus, only thing Is the voltage with koeo reads 0.71v and 0.68v engine running, so it looses 0.03v when engine running and still reads 2.4% at idle and won't learn 0%, I'm gonna clean the grounds again and try it again!

What scan tool are you using to read tps %? Any chance you can try a different one. Or try closing the TB blade until the tps reads .55v and see what the % does. .71v seems a little high.

Ok I set it to .55v an it reads 3.5% now, it won't learn the position, i did all the relearn procedures and as it will read 0.0% with key on engine off but as soon as I crank It, it jumps to 3.1% with 0.55v at the sensor, I'm using a regular autozone hand held scanner that reads everything except IAC counts and the voltage I use my multimeter! But everything reads exactly the same on my tuners HP tuner.

Just to be sure you are doing key off - unplug tps - key on for 30 seconds - key off - plug in tps for the reset procedure.

Also you never said what the voltage was between the black tps wire and battery ground KOEOff and KOEOn. This will check for a ground offset.

the voltage between the black wire and battery is only 0.01v difference, i don't think that will effect on anything, and yes i have tried leaving the key on for 30sec with sensor unplugged, after i turn the ignition off and plug the connector in, it will read 0.0% key on engine off but wen i crank the engine it reads 2.4 or 3.1%. This morning it read 0.4% first start up but after i turned it off and back on it went back to 3.1, honestly I'm stumped! I'm gonna buy new pcm next week and see what that does but meanwhile i'll keep trying, maybe it likes certain voltage at idle, my GM manual doesnt give me specific voltage ether, just says about .6v at idle.

When u say key on engine off u refer to key in the run position engine off right?!?!?!?