TXMach

Can anyone explain this in detail?

I installed the throttle body and the car started fine but would not idle. I adjusted it to idle a bit high (around 1100 rpm) then waited for it to get to operating temperature.

Upon reaching operating temp I re-adjusted it to idle around 800 rpm and test drove the car for a while. Everything was fine.

I parked the car overnight and went to start it up but it wouldn't start. I disconnected the battery and inspected all related vacuum lines and sensor connectors and all was fine. I waited about 15 minutes and reconnected the battery and the car started fine but was idling a bit high.

I let the car idle high until it reached operating temperature, then I turned the car off. I then went to adjust the idle with the engine off and tried to restart the car. It wouldn't start.

I'm stumped...

school boy

Make sure all the connetors that were unplugged during install are connected fully and locked in place. Also check and see if your gasket is sealing.

TXMach

Yeah, all that is 100% plugged up and there are no vac leaks. I'm thinking this is an electric issue maybe.

I know the Mach 1 TPS isn't adjustable, but I've read a few posts about setting the TB up with the IAC unplugged for a bit. I ran out of daylight so I haven't had a chance to try.

Stevo86

Anytime you are trying to adjust idle by way of the TB you should have the IAC unplugged.

The IAC is really just complementary to the mechanical adjustment. It only serves to increase idle for your A/C and fix some driveability stuff like RPM dropping too quick in a manual car when you push in the clutch.

TXMach

Excellent. That's what I wanted to hear. I feel like a loser because I didn't know that, but it wasn't in the instructions. I'll give that a try after I get out of work. Thanks a lot.

cliffyk

The adjustment screw on the TB is not an idle adjustment but rather a stop screw that when properly adjusted allows a specific amount of air to pass through the TB at "closed" throttle. Idle speed is controlled by the PCM which will use the IAC, fueling and ignition timing to do all it can to make the engine idle at whatever speed is defined in the tune. The adjustment of the throttle stop screw is part of this scheme.

Here is how to properly set the idle stop screw...

TXMach

Okay so I set it all up as instructed and it seems fine. I'm waiting a few hours now so the engine can completely cool down. I want to see if it will do a true cold start and idle properly. I'll post whether it's running properly or not. Thanks a lot for the info guys.

cliffyk

Make sure you let it idle for 15 minutes, that is an important part of getting the PCM to learn the new idle trim values...

TXMach

What I did was unplug the battery for the whole day while I was at work then came back and reconnected the battery. I started it up and let it idle.

As it idled I unplugged the IAC and the idle (which was at about 1200) did not change, so I adjusted the idle stop screw to about 700 rpm, then turned the car off and reconnected the IAC.

I then disconnected the battery for about 15 mins, then reconnected it and started the engine. I let it idle for about 10 mins then took it for an easy drive for about 20 mins.

I never gave it more than 20% throttle and never went faster than 60 mph. I clutched in to coast a few times and the revs dropped normally and the car idled at around 700 rpm to 800 rpm.

So I parked the car in the garage and now I'm waiting a few more hours until the engine is completely cool. Then I'll see if it's still good after a cold start.

You said to let it idle for 15 mins. I only did about 10. (didn't know better at the time) So I hope I didn't derail my settings or the PCMs learning.

Thanks again, I'll post with the results.

cliffyk

Then you have done nothing to fix the problem, I guess you did not bother to read the link I posted--THERE IS NO IDLE ADJUSTMENT SCREW.

Read the link and adjust the throttle stop screw properly...