Im having a hell of a time tracking down a problem with one of my 1990 TGP's.  So here is the issue, when you start the car it will idle around 1500 rpm and slowly get to 2000 rpm and then it will stay at 3000 rpm.  Also when your driving it at low speeds it runs great, but when you go WOT the boost gauge maxes out and the motor pops, seems like the fuel cutoff kicks in, since the car dosent accelerate, just jerks.  Ive traced all the vacume lines, fixed a couple i found leaking, swaped out the map sensor, replaced the pcv valve. I dont know what it is, it seems to me like a vacume leak, but I cant find it.  anyone have any insight on this ?  thanks  ;)

stuck IAC valve?

I swaped out the IAC with another TGP that runs good. and it didnt help.  Im going to Swap out the TPS and see if thats what is wrong.

adjust the vaccum modulator right near the ecm fuse box, there is a cable for the throttle right there, pop the clip off carefully move 1 hole towards the firewall this will lower the idle speed a lil, or will raise it if you moves it towards the turbo, for the WOT problem and the bucking but no acceleration but gauges are reading correctly and jumping up on the boost, I just had this same problem with mine, I replaced the spark plugs first, plugs wires second, and third most important the ignition coils packs/ Ignition Control module, test them for a spark by finding a good grounded bolt on the frame or engine, unplug 1 spark wire from 1 spark plug at a time, ground them out by clamping the threads of spare spark plug inserted into the unplugged plug wire to the bolt for the dogbone on the drivers side will do, have a friend crank the car over do this for the front three cylinder watching the spark jump across the gap anything but blue spark may mean a weak coil

Ok, so here is an update.

I replaced the plugs and plug wires, didnt help much on the two problems.
I checked the coil packs, they seem to have good spark.
checked the cruse control vacume control and moved cable one notch tword the firewall, didnt help.

So I figured I might as well change out some sensors, since it prob needed it anyways. So I replaced IAC, MAT, MAP,Temp,TPS, and O2.
I replaced them in that order, nothing made a change untill I got to the O2 sensor. The O2 sensor cured my bogging/poping/no acceleration problem. But I still have the high idle problem.  Ive swapped the computer out and the mcal with a known good working one and still no go. Checked fuel pressure, Checked again for vacume leaks, cleaned throttle body again.

Its just weird, if you start the car up when its warm it will idle perfectly untill you give it some gas then it will stay at 2000 rpm and wont come down, then if you turn the car off again and restart it its just fine again untill you rev the engine then 2k again.

Any thoughts?

Any chance your throttle plate is stuck open a little? There is a throttle stop screw.

When it idles low... does it idle rough?

I have the stop screw turned all the way in, its not touching the throttle linkage stop anymore.  when it idles it seems to idle smooth.

ok so I got the computer out and data logged the car,  when I start it up warm the iac sits at around 45 and it idles perfectly, when I give it some gas the iac sits at 65 and it idles high.  So it looks like its the computer making it idle high, I just dont know what its seeing to make it think it should make the iac open up.  I did see the O2 reading going from 100 to 800 like crazy while idling. maybe I have a bad injector dumping fuel in one cylinder or something making the O2 see rich?  maybe I will try ohm out the injectors this weekend. 

If nothing elese im sure learning alot more about this engine :)

Ok so I replaced the Injectors with Yellow top's and replaced the upper intake gasket. Still having the same problem.  when I datalog it, it idles perfect on startup but give it some gas and the iac opens up and the rpms go up to 2500 or so.  So the computer is seeing something. Ok so correct me if im wrong, but the only sensor on the car that can tell the computer if its lean or rich is the O2 sensor.  Unless there is something wacky with the MAP sensor readings.  when the car goes nuts the blm is around 135 and int is at 135-136.  but at startup when it idles good the blm is at 125 and int is around 125 also. 

The pcm was opening my IAC valve for no apparent reason as well... When I would come to a stop, it would close it abruptly. So when it was idling normal, I just unplugged the damn thing.

Have you checked the throttle body linkage itself to make sure it's not sticking occasionally and causing your high idle?

Since you said you're using a computer to datalog the car...Can you post or email me the datalog to take a look at?  mfewtrail @ windstream.net is my email addy, without the spaces of course(put them there to hopefully keep the spam bots from grabbing my addy).

same exact thing is going on with my tgp now with the linkage sticking

Quote from: letsjam on March 11, 2010, 06:54:40 AM
Ok, so here is an update.

I replaced the plugs and plug wires, didnt help much on the two problems.
I checked the coil packs, they seem to have good spark.
checked the cruse control vacume control and moved cable one notch tword the firewall, didnt help.

So I figured I might as well change out some sensors, since it prob needed it anyways. So I replaced IAC, MAT, MAP,Temp,TPS, and O2.
I replaced them in that order, nothing made a change untill I got to the O2 sensor. The O2 sensor cured my bogging/poping/no acceleration problem. But I still have the high idle problem.  Ive swapped the computer out and the mcal with a known good working one and still no go. Checked fuel pressure, Checked again for vacume leaks, cleaned throttle body again.

Its just weird, if you start the car up when its warm it will idle perfectly untill you give it some gas then it will stay at 2000 rpm and wont come down, then if you turn the car off again and restart it its just fine again untill you rev the engine then 2k again.

Any thoughts?

sounds to me you have something sticking in the throttle body , Did you try to shoot some type of cleaner in there..

Are you running a chip?

My linkage is all good, nothing hanging up there.  I might swap out the whole throttle body with my parts car. Maybe something is being stupid in that assembly.  I was running a chip and I just put in the factory chip... does the same thing :(