i have a 1992 gt and just changed to a proffesional products 75mm throttle body i set the tps to .98 and checked all the vaccum lines. I'm a little unsure what else to do. I also have a custom diablo chip burned. other than that the car is all stock except of course for the turbo kit. It starts and idles fine for about 15 seconds then lopes and falls on its face. When the car idles during the 15 seconds it idles nice and smooth. Any help would be great, or @ least a place to start.

 

have you tried setting the base idle screw under the throttle body? unplug the iac motor and set the minimum idle to somewhere around 700 rpm or so depending on camshaft and plug the iac back in. then reset the tps to .98v

 

Did you change the spacer to a 75mm as well? Are you sure there are no leaks around the TB gaskets?

 

make sure the wires didn't pull out of the iac motor. Double check the idle adjust screw as well.

 

there are no leaks on the throttle body or egr and the egr is a matched 75mm set. I'm going to try unpluging the iac and set idle, then plug it back in a reset the tps sensor. I'm sure it's something stupid that needs a little tweaking, unfortunetley the fine details are not my specialty, i'm good @ all the grunt work and no good @ the fine details.

 

For some reason, my car dies out if i quickly get off the throttle and press in the clutch after a full throttle run. I have that same throttle body(not saying its the reason) and a tune.... I cant figure out why its doing that exactly. I'm going to fixing some other things on the car and taking it back for a retune. Hoping that will fix the problem.

 

+1

I had a time with this shit in the past on my old 88 gt.

 

Your throttle blade setting is pretty critical on your setup. The IAC on those cars are REALLY slow to react and if you get your throttle plate open too far, you may still idle at a normal speed but when you rev it and come back down, they will hang the RPM for DAYS. It sounds like maybe it screws up when the motor goes closed loop and the IAC isnt fast enough to catch the glitch. Definitely keep the IAC around .98. Above around 1.10 they lose idle control. You may have to file the TPS a bit to get it to adjust right with the professional products throttle once you get the blade angle right.

 

is it possible its just a shitty throttle body? ive had problems like this in the past with a BBK TB that just wouldnt run for anything. swapped it out for a different brand and everything worked fine. havent heard the best thing about PP if you know what i mean

just a thought

 

i made sure the tps voltage was exactly .98 volts and the idle screw screw is were it is supposed to be, the car ran for almost 5 minutes last night in the garage then stalled. It's getting better, but i think a dyno tune is what i need. The Proffesional Products throttle body and egr seem to work great so i do not think thats the issue. i think its more a mass air and rich/lean setting

 

was it running fine before adding the TB? if so how would that be a mass air problem?

 

it ran perfectly before, but i talked to my tuner and he said it might screw up all the settings and need a new tune. Here is his e-mail

It's because of the larger throttle body, and unfortunately on an EEC-IV car (like yours), it's a PITA to correct (potentially). It has to do with the expected airflow in #'s/min vs. the actually #'s/min thru the TB. The PCM commands the IAC motor to open X amount, and when it does, the actual airflow is different than what's expected, let alone when the throttle is cracked open. Your adaptive strategy in the PCM will adjust to the best of it's ability, but sometimes it's not enough.

It may take me 30 minutes, or it could take me 3 hours...........it's really tough since we can't see what's going on (no OBD2 communication).

 

i see... hmm interesting

 

so now i have to get a new tune, i was thinking about buying an anderson pms system ans tune myself, but i'm not good @ tuning at all

 

Did you use the TPS electronics that came with the new TB? If so, try putting your stock one back on.

 

why should i do that ? just curious. I got the car running last night, i set the tps tp 1.04 and raised the idle, so it runs but not @ optimum performance, i still think i need a tune

 

Just something to try.

 

Just a thought but if you are using the stock IAC motor from 1992 you might want to check that it's not plugged up with crap or just not working properly. You are moving alot more air through there now (meaning that the MASS air meter calculations are different with more air flow) and the IAC motor might be not be able to react quick enough with the amount that is needed. Once that throttle blade snaps closed after a run and the IAC motor doesnt provide enough air, the motor will very quickly stall out. I know that mine was full of a black deposit from all the emmisions stuff they put on those motors. Also a bad TPS is also known to cause an irratic idle.... up and down surging and even stallouts

hope this helps Jay

 

thanks guys i will try all these and get back. I think i'm also going to buy a blow through tube to help smooth out the mass air defects on my kit

 

the car actually runs ok right now, i put the tps voltage @ 1.04 and raised the idle a bit, so it runs but not @ optimum capacity. I need to get rid of the badly designed mass air sensor and pipe it is attached to. I want so badly to have a 90mm lighning mass air sensor in it's place, if someone knows how to accomplish this i would be grateful. I need to have someone redo the pipe coming from the intercooler to the pipe going to pipe that attaches to the throttle body. This pipe also has the blowoff valve attached to it. I need the pipe to have a nice straught length on it and the inlet for the mass air sensor electronics. here are a few pictures of what i need and what i currently have. the picture of my kit shows the area were the pipe goes (behind the zex brain box in the fenderwell)