wayshegoes

was out for a drive Sunday and after 30 minutes of driving fine I come to a red light, I am stopped, however RPM is up 2500 ish, shift light is on, car is stopped, I push gas pedal and let go, RPM jumps up and then goes back down to proper idle

I drive on, next light, same issue, get home connect cable, I notice if i press gas and let go quickly, sometimes the TPS value goes up and down correctly, others it will go up, but not fall back down

Is this a sign that the TPS sensor needs to be replaced? I already replaced it last year, any recommendations on where to get a good OEM one and not a made in China POS?

many thanks,

Jeff

jay123

Yes that is def the TPS giving you the trouble. In Ontario try NAPA for a OEM replacement.

thtanner

iTrader: (1)

RockAuto
ACDELCO 213905 {#17111606} GM Original Equipment

http://www.rockauto.com/en/moreinfo.php?pk=87472

Will probably still be made overseas somewhere. You can also try BWD brand (carried @ O'Reilly's if you have them) - they are often made in Taiwan not China.

JA411

Check for throttle blades sticking (clean carbon bluid up). Also for binding cable or linkage. Don't forget about the floor mat for pushing on pedal. Have seen all of this come into shop for high or iradic idle, with or with out SES lamp and codes.
Joe

wayshegoes

new TPS and still the same problem, however acceleration is much better!

I am going to try cleaning the throttle blades and see if it fixes

wayshegoes

finally got time to clean throttle blades, issue continues, what would be my next step

Bob88GTA

iTrader: (2)

Have you pulled the IAC out and cleaned all that carbon out?

Bob88GTA

iTrader: (2)

Then follow this
https://www.thirdgen.org/forums/tpi/...988-trans.html

wayshegoes

will try, thank you

Bob88GTA

iTrader: (2)

Whatever you do, DO NOT TRY TO UNSCREW THE IAC BY THE CONNECTOR!!!

Use a large socket..I think it 1 !/8"

wayshegoes

following the last suggested steps, cleaned the IAC, re-installed, insert A&B jumper on ALDL, wait 30 sec, pull connector to IAC, start car and adjust idle, cant get the car to start, at most it starts and dies, wont keep running

suggestions?


i didnt take the pintle all the way out in fear of breaking it, but did get it cleaned with it extended, this was replaced recently, but it was a china POS, perhaps I should replace it with a AC delco, as the AC Delco TPS sensor was much better than the china POS one I had previously?

thanks in advance for all the help

Bob88GTA

iTrader: (2)

When you went to start it, the idle was to low. You may have to turn the stop screw out a bit till it will idle on its own, barely. Then do the idle set.

Delco ones worked best for me

wayshegoes

So I had time to complete the steps, got the car to start by turning the idle screw out, got the RPM at about 500 in neutral, 5 speed car, however when i plugged the IAC connector back in and re-started the car was idling very high, maybe 1500, so I turned the screw back, that normal?

did take for a drive and the sticking throttle problem seems solved, dirty IAC, going to replace with a AC Delco, as this was a china POS

wayshegoes

Does the EST wire need to be disconnected while performing the IAC reset?

I have read yes and no, and am confused

Bob88GTA

iTrader: (2)

Some say yes, others say no. I done it both ways. It don't matter.

wayshegoes

How does one get the rpm to stay at the set value after the iac is plugged back in?

Bob88GTA

iTrader: (2)

Theoretically speaking, the computer should keep it in check.
Is your TPS set correctly?
Did you drive the car after the IAC Reset to re-learn?

wayshegoes

No, I did not drive after, i adjusted RPM back down and then drove it, the TPS was at .53

I will go through steps again, this time after plugging IAC if I have a high idle, maybe I need to let it run for a min or two? I noticed the excessive idle and shut the car off

not sure what TPS was at when idle was high, didnt check, will check next time


many thanks for all the great help

Bob88GTA

iTrader: (2)

After IAC portion is set, you still need to reset the TPS before you even leave the driveway. .54volts is where you want. Set it, THEN go for a drive.

Johngypsy

You did not say what year was your Iroc ?

If u have the 1985-1989 you have the mass air flow, this is and could be a few major issues to not, I'll tell u what happened to me and how I fixed my issues doing the same exact issues, so please follow this process to get your car going right,

First off the lowest issues results:

1) the mass flow sensor, if u have a can cleaner of mass air flow or just pick up one can for about 9-13 dollars (starts with a C- forgot the name of it but works great) clean the electrical parts inside of it being careful not to touch the connectors, this mass air flow allows the rpm to flutter up and down thus causing air not to flow due to dirt or decree, common issue we all have with these as we have to replace them about once every 2-3 years depending how much u drive it,,, this should be your first choice to start with,

2) take a digital reader and go to YouTube and search how to check your fuel injectors pulses, this can also do the same for fluxing your motors Rpm's thus causing 1 bad injector to not flow the proper amount of fuel into the motor, causing the the motor to rev higher and lower, the average amount of pressure should be 12.5 to 14.7 and should all be in conjunction to less then .7 at most, if your readings are more then 1 amp apart u will have to change your injectors, even if it's just 1 bad one do them all for only 40-50 dollars for all 8 of them, we all buy them from the lady who sells them in at South Bay fuel injectors for cheap and they are the best in the business (1 (516) 442-4708) grab the bosh III series 24 ponders, depending what size motor u have the 305 or the 350 Tpi she will get u the right set up with all the gaskets to get u going fast,

The reason is the injectors sometimes get clogged and dirty (common for Tpi cars) as the motor will do the same issues u are having and thus causing the same issues for the engine to run hi and low rpm's

3) the other thing is this but again don't know what year your car is: this issue is over looked 90% of the time as 3rd gen guys get stumped about it,

In the far back of the car, there is a solenoid that is called for the egr, check to see if that is working properly or it will sometimes get hot therefore causing the switch to get hot and thus making it not to work properly causing a internal vacuum leak thus making the rpm's flux when getting hot, it's worth a try at most,

4) next i would like you to check your coil that is located in the back of the distributor sounds crazy, but sometimes this will cause also the car not to run good rpm's from contact, basically a tune up part

5) and last part to check, all of your vacuum lines for cracks that can not be seen that might have small cracks into them that are all under the hoses, especially the one that goes to the egr and throttle body,

As Joe stated in this form, clean the throttle body good, as u done but this time take it off by 4 large screws (2 top - 2 lower) replace with a new gasket as sometimes the gasket may also be leaking to, a small job about 40 mins at most, u can get a can of carb spay and start the car and soray away if u see the motor reving hi when spraying u have a leak, my personal option would be take it off and do a full cleaning to it all, not just spray but elbo Greece to get all the black gunk out of her right

Hope this helps

If was my car I would check all the injectors first with a small meter that u can see steep by step on YouTube

Good luck and please post back and tell us all that it's running like a champ again

John
Houston Tx

wayshegoes

Update

I followed your suggestions and got the car started with IAC unplugged, got idle around 500 -- how would I know for sure what idle is, I used the dash gauge, but know it is not accurate enough

Now when the car starts, still needs 3-4 cranks, the idle is up about 1500 and drops down, now sometimes it drops to about 1000, sometimes lower to bout 700ish