'87 TII - Idle Too Low Once Warmed Up - Best Solution??
 

Hey guys,

My '87TII is finally back on the road, it's such a pleasure to be driving again but I have recently noticed that the idle is really low once fully warmed up. I have been driving the car longer and longer and have been able to drive it for a half hour straight, so it's definitely warmed up.

It idles at 1200 or so and then gradually winds down to around 600 rpms once the engine is up to temp. Once the car is hot the throttle tab is resting on the throttle stop and the TPS is at 20% according to the Rtek. I have checked the throttle cable and it's fine, I have all new vac lines and gaskets as well - which were all double checked yesterday.

How can I raise the idle a little bit other than the BAC, it seems like it's out of range for the BAC valve to compensate - the screw on the BAC was almost all the way out and it didn't help, yes the initial set coupler was jumped.

Should I try to move the throttle stop screw to keep it open a bit or what?

Thanks so much for your help.

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Just a note, I have heard that gunk inside the TB can cause the low idle but this is a new TB and was cleaned before being installed recently.

It's weird cause it runs awesome when warmed up but just idle a bit too low, it hasn't stalled yet but it comes close at times.

i would adjust the idle manually by the screw behind the TB

"the scew"? which screw?

I just want to adjust the idle speed of the fully warmed up motor, I don't want to mess with the "fast idle".

whats it idle at when cold? what AFR do u have at idle when warm? if its too lean the car might idle low as well.

TIIs have the idle adjust screw on the BAC valve, it's not on the TB like an NA so if it's all the way out, that's not an option.

Okay the RPMs when started cold are only like 1,100 - 1,200, thats a bit low for the cold fast idle in my opinion anyways, so I made some adjustments to the Fast Idle Cam screw once the motor was hot. Basically by backing that screw off I can keep the rpms higher even when the thermowax is fully extended. I was adjusting the TPS as needed to keep it reading 20%.

This seems to have helped quite a bit but why would my idle have dropped like that? I thought it was supposed to idle at 750 when the throttle was agint the stop screw. I have only driven the car for like an hour total since putting the whole motor and everything back in the car, could this just be everything settling in, it seems like the whole rpm range at idle just slid down a few hundred rpms.

maybe the motor building compression has something to do with it?

Well the motor itself has 1,500 miles on the rebuild but I just resintalled the motor recently.

I don't know, last week I could go for a drive and come home and the idle would be 800rpm steady when hot. The only thing I did was take the TB off to put a hose clamp on a coolant line, maybe I torqued some thing when I was twisting the TB around.

I am also curious why it seems like the BAC valve stopped responding, I checked it's resistances and they were good, maybe it was just too low for the BAC to make up for it.