I'm Back! '90 GTUs

[project86]

I think I may have mentioned that I developed an idle surge. I initially had the screw in the top of the TB backed all the way out after the emissions removal and it held around 900RPM.

Lately its been idling around 1500 and surging to 2000 intermittently. So I was reading on the other forum about it and found one thing that said adjust the screw so I screwed it all the way down and it brought it back to around 900-1000. After I started driving it the idle jumped back up to 1500 but didn't surge any more and then settled back down to 900. Still no surge so thats good.

Do you think by BAC could be bad? I know i dont "need" it but it does help with idle speed. I suppose I could unplug it and see how the car responds.

[infernosg]

Originally Posted by project86

I think I may have mentioned that I developed an idle surge. I initially had the screw in the top of the TB backed all the way out after the emissions removal and it held around 900RPM.

Lately its been idling around 1500 and surging to 2000 intermittently. So I was reading on the other forum about it and found one thing that said adjust the screw so I screwed it all the way down and it brought it back to around 900-1000. After I started driving it the idle jumped back up to 1500 but didn't surge any more and then settled back down to 900. Still no surge so thats good.

Do you think by BAC could be bad? I know i dont "need" it but it does help with idle speed. I suppose I could unplug it and see how the car responds.

There's a procedure for adjusting this screw in the FSM. IIRC, while idling and warmed up you have to ground one of the pins in the green check connector located elsewhere in the engine bay and then adjust the screw so the TPS voltage is within a certain range.

EDIT: In the '89 FSM it's in section F1. Pages F1-15 and 16 cover idle adjustment, pages F1-40 and 41 cover idle control and checking the BAC, and page F1-83 covers checking the TPS. Found here: http://www.wright-here.net/files/man...mission_NA.pdf

[project86]

Originally Posted by infernosg

There's a procedure for adjusting this screw in the FSM. IIRC, while idling and warmed up you have to ground one of the pins in the green check connector located elsewhere in the engine bay and then adjust the screw so the TPS voltage is within a certain range.

It wasn't the TPS I was messing with. That we got adjusted correctly a while ago. I'm referring to the "idle screw" on top of the throttle body/UIM.

[infernosg]

Originally Posted by project86

It wasn't the TPS I was messing with. That we got adjusted correctly a while ago. I'm referring to the "idle screw" on top of the throttle body/UIM.

Yeah, there's some other crap you have to do when adjusting idle. You're not supposed to just turn the screw like with a carb. I updated my post above with info from the FSM.

[project86]

Originally Posted by FC Zach

Kyle, that's what he's taking about. . There's more to it than just turning the screw.

Originally Posted by FC Zach

Check your manual.

Originally Posted by infernosg

Yeah, there's some other crap you have to do when adjusting idle. You're not supposed to just turn the screw like with a carb. I updated my post above with info from the FSM.

Oh ok. I gotcha. I'll have another look then. It seems that it did make some difference though.