Mind boggling issue... hunting for help.
Mind boggling issue... hunting for help. Okay, so I recently gave my car a makeover... new heads, new cam, fast 90 intake with the fast 90 throttle body. Installed everything and hooked everything back up (first time doing this, what a huge learning experience). I start it up and the idle is rather high... I would guess close to 2,000 RPM. So I jump on here, run some quick searches and go return to the car for the vacuum leak hunt. I'm unable to find anything... I tighten up the intake bolts a little bit, make sure the throttle body is secured, vacuum hose on the rear of the intake is hooked up, and map sensor is secure. All seems well, so I fire it back up. Same problem. So now I decide to unplug the throttle position sensor and start it... wow, idle is perfect between 800-900 RPM. Now I'm really stumped. Does anybody have any idea what might be going on here?? I figured if it were a vacuum leak that unplugging the TPS would have no effect on fixing that, but the LS1 world is still very new to me. Car is an automatic... and I plan on having it tuned very soon; I just figured it would idle somewhat better than it is now. Going to check voltage of TPS later today and see if my reading is anywhere near the .61 value that people have stated to try and set it at, do the TPS relearn process, and then try starting it again. It's really frustrating. I'm being as patient as possible, been working on this project for almost a month now taking my time and doing it right, now if I can just get this idle thing figured out, I'll be thrilled. Thanks to anybody that can share some insight.
FOOTNOTES:
CHANGES: New heads, cam, intake, throttle body
PROBLEM: High idle
NOTES: Car idles perfect with TPS unhooked, A4
WANTED: Insight to correct high idle problem
FOOTNOTES:
CHANGES: New heads, cam, intake, throttle body
PROBLEM: High idle
NOTES: Car idles perfect with TPS unhooked, A4
WANTED: Insight to correct high idle problem
Well did you try and reset the TPS? Scan and make sure it's at (you didn't say what kind of car so I'll assume f-bod with a cable driven TB) 0%TPS. If you don't have a scanner or tuning software, there's not a lot you can do though... Back the TB blade's set screw down to physically close the blade the blade a little and reset the TPS and rinse and repeat, though if you can't scan to verify 0%TPS you will be making guesses until you get it in front of a tuner. I wouldn't get all worked up over it, assuming there are no leaks, it's not a big deal, just needs to be tuned.
What's the correct 0% TPS voltage again..
.5V < X < .69V or something like that?
Mine's at .55 currently
can I get some confirmation....?
Well did you try and reset the TPS? Scan and make sure it's at (you didn't say what kind of car so I'll assume f-bod with a cable driven TB) 0%TPS. If you don't have a scanner or tuning software, there's not a lot you can do though... Back the TB blade's set screw down to physically close the blade the blade a little and reset the TPS and rinse and repeat, though if you can't scan to verify 0%TPS you will be making guesses until you get it in front of a tuner. I wouldn't get all worked up over it, assuming there are no leaks, it's not a big deal, just needs to be tuned.
I'm still not sure if I can rule out a vacuum leak, so perhaps I'm just not finding it??? Having the TPS unhooked and it running fine just had me confused. I'll get it over to a tuner hopefully by day's end, but will give the "Bumpstop" mod a try here in a little while. Thanks for your responses guys! Keep chiming in if you have any other thoughts.
Do you have the ability to see what your TPS percentage is? Like an OBD2 scanner or other tool? If so, you can more accurately set your TPS and throttle blade position. Just because you reset it to 0%, doesnt mean the blade stop screw isnt too far open beyond what the IAC valve can offset.
If you can see your TPS % as seen by the ECU, adjust the blade bump stop to completely closed. Reset the TPS. Ensure it shows 0%. Then slowly screw in the stop screw until the TPS shows 2% (3% if you have a larger cam). Then reset the TPS to 0% again. This will get you close.
If you can see your TPS % as seen by the ECU, adjust the blade bump stop to completely closed. Reset the TPS. Ensure it shows 0%. Then slowly screw in the stop screw until the TPS shows 2% (3% if you have a larger cam). Then reset the TPS to 0% again. This will get you close.
