Extended cold start

[Tedmag1]

After changing bad injectors on my 89 the idle upon the first start was up around 1500 rpms I quickly lowered the idle adj screw all the way down to get to 600 rpms at a stop in drive, I adjusted the tps to 0.54 volts but now I have to tap the gas pedal when comming to a stop in order to get it to idle down it is like it hangs up I am not sure if it is the IAC valve or the linkage isjust hanging up a little,it runs excellent except for that, and the first initial startup takes an extended cranking I adjusted my fuel pressure regulator to 47lbs key on not running, any ideas would be welcome by the way the injectors were purchased fron jon at fuel injector conection

 

[Hib Halverson]

That "screw" is not an idle speed adjustment. Idle speed is controlled by the ECM. The adjustment you moved is called "minimum air" is not intended for idle speed control. If you change it, the engine will idle poorly and may have trouble starting. My advice is to solve the problem that's causing the high idle then reset the "minimum air" adjustment per the Service Manual.

Also, do not use fuel pressure to solve a starting problem. Use the fuel pressure testing procedure in the service manual to readjust that to factory specs.

My advice is to obtain a factory service manual and follow its instructions for diagnosing a problem with idle speed and stability.

Also, start looking for vacuum leaks along with problems with your IAC (idle air control), accelerator cable, throttle linkage or the throttle body itself.

 

[Curious George]

As Hib said, start looking for a vacuum leak. If you removed the TPI plenum and runners to replace your injectors, there are plenty of gasket surfaces for a leak to start. Everything you did to "fix" the high idle on a TPI motor is a no-no.

CG

 

[Tedmag1]

well thanks for your quik response anyway i went back to square 1 it idles at 1500 rpms reset IAC ACCORDING TO THE MANUEL set tps to manuel specs still high rpms had to lower screw all the way down to prevent the car from blowing up the car will run good there but like i said i have to tap the peddle to get it to kick down to 600 rpms otherwise it will be at 800 rpms any other suggestions

 

[Tedmag1]

i realize that(about tps and idle screw adj.) but it was the only way to keep motor from running at 1500 rpms it runs good exxcept that i have to kick down the peddle comming to a stop or it will idle at 800 rpms

 

[Curious George]

As far as diagnosing the problem... I would start by putting the ecm in diagnostic mode by grounding pins on the ALDL connector. Reference Manual: Chapter 10: Emissions Equipment: ECM ALDL

Turn the key ON, but do not start the car. Connect a paper clip bewtween pins "A and B". This will extend the IAC and block off the idle circuit in the throttle body. Wait about 20 seconds after shorting pins A and B together, then disconnect the 4-pin IAC plug under the hood. Turn OFF key and remove paper clip.

Now start the car and see where it idles. If it does not idle (or idles very very low) then this would indicate the IAC is doing its job of regulating the idle. Although you could still possibly have an issue in the IAC somewhere. However if it continues to idle high, you have a vacuum leak somewhere.

CG

 

[vetteoz]

i have to tap the peddle to get it to kick down to 600 rpms otherwise it will be at 800 rpms any other suggestions

TB is binding up somewhere
Check the cable for binding ( disconnect cable and see if it will return to correct idle after revs ) and also the TB shafts for wear.When worn they can go off center and jam up , not returning fully to the closed position

 

[G Winter]

TB is binding up somewhere
Check the cable for binding ( disconnect cable and see if it will return to correct idle after revs ) and also the TB shafts for wear.When worn they can go off center and jam up , not returning fully to the closed position

I have this problem with mine right now. It is amazing how quickly they go from almost no wear to binding.You can only feel it with the engine shut off, the vacuum pulls so hard you can't move it.

Glenn