Ok so my 1985 z28 has a 350 crate with tpi system. after you drive a few miles it starts to act funyy. if you give it any gas over about 1/8th throttle it tries to die. but if u floor it it will run just fine also after you break 2500 RPMs it is ok. the idle is really high even with idle backed all the way off around 1500rpm in park or nutral. If you let off the gas while going it dies after a second some times. the check engine light is only on when you are not accelerating. i just put a new throttle positioning sensor on it so any ideas? and i took cat off.

 

The car seems to run bad when in closed loop, (goes to open loop at WOT). Thishints ata sensor problem, because the ECM normally looks at all sensorsat part throttle, but ignores most of them at WOT. Get the car scanned & see what the codes are. The high idle could be due to many things, bust most likely a bad IAC valve,or a vacuum/air leak on the engine side of the throttle valve.

 

ok so i have checked the mass air sensor i was told if i unplug it it should run right if that is the problem. i put new ffuel filter on it. i just started pulling plugs and they are black. so i know it is getting to much fuel any one kgot an answer?

 

Get the car scanned & stop throwing parts at it. It is usually cheaper.

 

yeah im taking it to a shop this weekend but mainly only done a tune up on it just replacing the parts that arnt new since most of it is.

 

ok so i got it checked shows up tps sensor. i had changed all plugs wires cap u know a tune up. It ran good then bout 15 miles later back to normal. i drove home 20 miles with constant pressure ongas check engine light never came on and it never ran bad. so im gonna try just boosting the idle a little bit see how that helps.

 

did you replace the tps? readjusted it? how did it run after?

 

i just put a new one on it and it ran worse after words doesnt even want to idle when your stoping. if i keep constant pressure on the throttle the car wont mess up at all just as long as i never let off the gas all the way