I have some wierd things happening in open loop. The idle varies from 500-800 rpms and sounds like it is gasping for air. Once the car goes into closed loop, the idle is smooth as silk.

What could be causing this?
I've checked everything. All connections are tight, and the TPS/IAC are set correctly.
The TBI is clean as well.
Vacuum? (if that is the case, why would the idle be smooth in closed loop?)
I'm really perplexed by this.
This is only happening when I start the car up. Once the car is warmed up, everything is 100% fine.

 

I had the same symptom on my car a few years ago, too. I then readjusted my idle speed screw ( a 1/8 or 1/4 turn or so screwed in) and then it disappeared. It was probably because of the tip of the idle screw "drilling" itself into the idle stop pad where it seats. When I further expected this spot I could see a small "pit".
With your air cleaner removed, actuate your throttle by hand and look at the area where the idle screw gets in contact with the throttle-lever stop. When you can see a wear mark that goes noticably into it, try adjusting your idle speed screw.
Whatever, readjusting it did help me. Hope this helps you.

Andreas

 

Okay thanks for the tip, I'll check the idle out after, but I have to wait till it goes into closed loop. Open loop it is so wild I can't adjust it at all.

 

Try cleaning the IAC passage way.
And then reset the min idle speed.

 

Okay I reset the idle and cleaned the IAC passageway. Going to let the thing cool off and check out the idle and let you know.

 

I guess it's running a bit better. The idle has mellowed a bit, but is stalling on startup.... Once I get it in gear it acts up for about 30 seconds then goes pretty smooth. I may have adjusted the idle too low.
Other than that, it seems to be running pretty good.
Thanks for the help.
I'll probably end up turning up the idle screw another 1/4 turn and seeing what happens. Seems pretty close but maybe it is a vacuum leak I haven't found.
I'm hoping.

 

It looks like you are coming closer.
Good luck !!

A.

 

Yeah it is still doing it.... I've narrowed it down to either it being a vacuum leak, or my choke?
Could it be the choke causing all this havoc?

I'm guessing it could be, because it seems to happen intermittently now, but I have no clue what to try, except maybe finding some vacuum leak that I missed.
It seems to do this:
I start up the car...
Idles around 1200 or so....
Put it in gear... down to 750... (normal idle)
hit accellerator...
engine idle goes down to around 450 rpms and nearly stalls, picks back up with very light touch on throttle... (sometimes barking the tires..)
It varies from around 450-1000 rpms until it goes closed loop and idles normally again at around 750.
Could I be running lean, or is the choke preventing the engine from idling properly?
Something's not right.

 

TBI's don't have a choke per say. It's all controlled by the ecm. Why is your car idling so high in closed loop or when it's up to normal operating temp? My car idles at 525rpm in gear.
I'd keep checking for a vacuum leak somewhere.

Steve

 

The cam is to blame for that, I think. I can attempt to bring the idle down to around 500-550 and let you know what happens.
I can guess right now. Bog.
Has a little to do with the motor/cam in the car now. It's a radical change from stock.
I changed the idle down... maybe that will do something. I hope it will work.

Edit:

It's now idling around 550 now.
Engine is smooth, but the symptoms persist, until it goes into closed loop. Like I said, when I push on the throttle, the rpm's go down rather than up. I literally goose it to keep the engine running.
Sorry about not stating the modifications on my car.
I'll show my sig.
It must be bog!

Edit:
Now it's running worse. I might have to bump that idle back up. Have to wait till my wife gets back from work tomorrow morning.

 

I had almost the exact same problem. I rebuilt my TBI and it stoped. That might not be the case in your situation, but it is only 25 bucks at AZ you should try that.

 

I kept the idle around 550 rpm and backed off the fuel pressure.
Car is running a LOT better than I expected. However, I also obtained a TPS for the TBI unit.
I have the feeling that my TPS was bad from the beginning. I replaced it and voila! A lot of the problems I was having have vanished.
No wonder I have been so frustrated!
At least the car is idling and accelerating better. It still bogs a tad but not at all like it was before!
It's way too windy out here today, so I will work on it a little more tomorrow and let you know if it makes a little bit of difference with the pressure being backed off a little more.
I still sense a vacuum leak. I think I will take it to a shop and have them check the vacuum lines just to be sure.
But YES it is running a ton better than it was!
Everyone has helped guide me along.