OK, I recently installed a ScanGaugeII and have been monitoring different PCM things. I noticed that every once in awhile my TPS would go from 0% at idle to some random number, like 6%/8%/4% and I think I even saw an 11% at one time. All I would have to do is shut the car off and restart it and it would be back to 0% again. I decided to replace the TPS sensor with a Standard brand one from RockAuto.

I installed it and when the car is not running but when I have the key turned on I am seeing a TPS angle of 0%...great, that's what it should be! As soon as I start the car (warm or cold) it goes to 3% and my idle is just fine at around 800rpms. Now after I take it around a couple blocks my TPS reading at idle goes down to 2% and then a little bit later it will drop down to 1%. At this time my car seems to be idling at around only 700rpm's or so. Then when my TPS angle decides to drop to 0%, the idle goes back up to around 800 or so. I don't know how the heck my TPS angle could be changing like that, as I KNOW it's not physically moving as the sensor says it is. My IAC counts are in the 55 area. The car runs and idles just fine, just I am confused as to why I am getting these different TPS readings when the throttle is not physically moving.

I do have a ported/polished throttle body that had a bit too much removed around the throttle plate which allowed too much air through at idle. I had the guy who did the polishing aluminum weld my idle air hole shut because with it opened up my IAC count was VERY low and the car tended to idle a bit higher than it should and took forever to come down when coasting. Now with that idle air hole closed up, like I said, I am seeing IAC counts in the mid 50's with this new TPS sensor. I do recall that with my old sensor I was seeing IAC counts in the mid 20's....

BTW, my replacement Standard TPS sensor is spring loaded while the stock one I took off the car is not. Is the stock one supposed to be??? I would think it would be more accurate if it was spring loaded.

does anybody have any idea to why my TPS sensor seems to have a mind of it's own?? lol

thanks!!!

 

update:

I cleared the PCM and tried it again with the new TPS sensor....did the same thing and this time my idle was at around 1,000 rpms. I then swapped in my stock TPS sensor and all is well after I started it up. It had 0% TPS and my idle was ~800rpms. I think either the new TPS is bad or it is calibrated a bit different than the stock one....either way it definitely seems to be TPS related seeing everything is fine with the stocker back in.

 

That's what you get for using aftermarket electronics. They're cheaper because the tolerances just aren't there. Next time buy genuine GM and you won't have this problem!

 

FYI .......LS1 computers reset TPS readings to 0% on startup. If you crack the throttle idle screw while running to get a 5% TPS then shut off the motor it will read 0% on start up.

 

lol, my stocker was acting up again so I decided to try a different brand other than Standard (who's known for high quality ignition parts and whose high end brand is Blue Streak), as I tried two different Standard ones and they both did the same thing. So, I went to Autozone and picked up a well known cheap brand TPS named Wells just to see how it behaved. I opened the box and it's the SAME thing as the stocker and has the same crappy construction as well as the same numbers and letters as the stocker. It even had the raised area on it but it didn't say "AC" on it like the stock one does. The way it looks, the stock TPS is made by Wells for AC.... As of right now the new Wells/AC TPS seems to be working, as I drove it ~50 miles and it didn't act up. The stock one would normally act up within 10 miles or so.

 

problem solved....


found out my old TPS is bad as it read something other than "zero" after a while of driving when at idle. Tried replacing it twice with Standard brand ones (which is the brand I prefer for all ignition related components, Blue Streak is the high end brand of Standard) and both of them did not work, they would immediately start out at like 4% (at idle) and then randomly go down to 0% and then back up to some other number all the while my idle would go from 700rpm to around 900rpms. It's like my PCM was trying to "learn" the TPS sensor like it was not calibrated the same. At idle my TPS voltage was always between 0.50V - 0.60V (AutoTap only reads to the tenth of a volt, and it reads 0.5V at idle running), so everything checked out there. I will say that the Standard ones had -a lot- better build quality when comparing it to the stock AC one.

I then tried a cheap Wells brand from Autozone and that seemed to have done the trick. I also took notice that the Wells brand was 90% identical to the stock AC one. It had the exact same mold, exact same patent numbers stamped in it, exact same inerds and sloppy build quality and it even had the same molded in raised circle that the stock one has "AC" stamped in it. The Wells one had the molded circle but just didn't have the "AC" stamped in it. I am pretty confident to say that the stock AC sensor is made by Wells or they both are made by some other company.