Throttle position sensor problems after comp cam 306 instal
Thread Starter
Staging Lane
Joined: Mar 2019
Posts: 59
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Throttle position sensor problems after comp cam 306 instal I recently just put a comp cam 306 in my 97 Firebird formula with the lt1 engine I got all the parts that was required for this cam and it ran fine for a few days but now the throttle position sensor code keeps popping up on my dash, Ive replaced the sensor 2 times now and Ive had a shop look at it and they said there getting a good reading from it and I could just need a tune to make it run right, the car will sometimes die if I get on the gas when in neutral and when Im driving itll run fine but when I take it out of gear to slow down the rpms will stay at 2000
the only mods Ive dont to my car is comp cam 306, Holley 58mm throttle body, k&n cold air intake, egr and air pump delete, hooker shorty headers, 1.6 rockers, new GM performance timing chain, msd Opti and plug wires, and coolant bypass mod
the only mods Ive dont to my car is comp cam 306, Holley 58mm throttle body, k&n cold air intake, egr and air pump delete, hooker shorty headers, 1.6 rockers, new GM performance timing chain, msd Opti and plug wires, and coolant bypass mod
Thread Starter
Staging Lane
Joined: Mar 2019
Posts: 59
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Between this, the opti and the stalling, it seems to me that it doesn't run fine.
The 306 is a lot of cam for a stock displacement LT1....plus you installed a bigger TB.
YOU NEED A TUNE......NOW!
KW
In order to get rid of the TPS code you will have to get the voltage back on track which means you will have to either solder in a new adjustable TPS, or slot the holes on the stock one, connect a volt meter and adjust voltage for closed and WOT.
OR
Just put the stock TB back on. For a cam only, stock CID engine you don’t need a larger TB.
And yes, you need a tune for that sized cam. You can run around as long as you don’t go WOT, but it also may run pig rich.
OR
Just put the stock TB back on. For a cam only, stock CID engine you don’t need a larger TB.
And yes, you need a tune for that sized cam. You can run around as long as you don’t go WOT, but it also may run pig rich.
Thread Starter
Staging Lane
Joined: Mar 2019
Posts: 59
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Ive checked the voltage and I was getting a good reading from it and Ive also had an adjustable throttle position sensor on there but it didnt solve any of my problems, Ive also had a shop check it out and they even said they was getting a good reading from it as well and they said it may just need tuned but idk if theres more to it than just a tune or if its just that simple
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Staging Lane
Joined: Mar 2019
Posts: 59
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Im not sure what code it was, when I replaced the sensor I cleared the code and it still was doing the same thing as the old sensor and no code has popped up yet, Im guessing I havent ran it long enough for the code to pop up but its still messing up and not running right
OBDI
21 Throttle Position (TP) sensor circuit (signal voltage high)
22 Throttle Position (TP) sensor circuit (signal voltage low)
OBDII
P0121 Throttle Position (TP) sensor circuit insufficient signal activity
P0122 Throttle Position (TP) sensor circuit low voltage
P0123 Throttle Position (TP) sensor circuit high voltage
21 Throttle Position (TP) sensor circuit (signal voltage high)
22 Throttle Position (TP) sensor circuit (signal voltage low)
OBDII
P0121 Throttle Position (TP) sensor circuit insufficient signal activity
P0122 Throttle Position (TP) sensor circuit low voltage
P0123 Throttle Position (TP) sensor circuit high voltage
TECH Veteran
Joined: Apr 2008
Posts: 4,985
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OP
you need to stop. If the tune is not for a 58mm TB, which you don't need, you will burn up your trans sooner than later.
Even with a tune for the 58 to correct line pressure per throttle blade position most after market TB's need "modification" to work right. This involves either drilling the RIGHT size hole in TB where the Idle air inlet hole is on a stock TB. Don't blindly drill this hole. You need scan software to read IAC counts and take baby steps in drilling to get IAC counts to 32 (30-35) at idle with engine fully warmed up.
TPS on larger TB
slot the 3 holes in TPS so you can "clock" the TPS back so you have about .67vdc blades fully closed and 4.5 vdc fully open
Cam, you need a PCM tune
and if your intake manifold was not machined for 58...that you need to do that also and don't do that wit the manifold on the motor
you need to stop. If the tune is not for a 58mm TB, which you don't need, you will burn up your trans sooner than later.
Even with a tune for the 58 to correct line pressure per throttle blade position most after market TB's need "modification" to work right. This involves either drilling the RIGHT size hole in TB where the Idle air inlet hole is on a stock TB. Don't blindly drill this hole. You need scan software to read IAC counts and take baby steps in drilling to get IAC counts to 32 (30-35) at idle with engine fully warmed up.
TPS on larger TB
slot the 3 holes in TPS so you can "clock" the TPS back so you have about .67vdc blades fully closed and 4.5 vdc fully open
Cam, you need a PCM tune
and if your intake manifold was not machined for 58...that you need to do that also and don't do that wit the manifold on the motor
My 97 Chevy truck needed a TPS relearn when I put a bigger throttle body on it. I tried hogging out a TPS to make it adjustable but that was the wrong answer. It had my line pressures maxxed out on the trans too. Relearn fixed it right up.
Thread Starter
Staging Lane
Joined: Mar 2019
Posts: 59
Likes: 0
Ive been running this throttle body on the car for about 2 years now and havent had no issues until I put the cam in the car and the only code popping up on my dash is for the throttle position sensor Im planning on getting it tuned soon for everything I have done on it but Im just wondering if the tune itself will fix everything or if there just something simple I can do before I tune it to make it run right for the moment
Tuner should be able to tell you whether or not your throttle is at 100% when at WOT. If you didn't know it should be 4v open and ~.7v closed and the voltage should change smoothly as you gradually increase/decrease the throttle. Writeups on this all over the place. I think shbox has one as well- www.shbox.com