Hollo, 91 305 Tbi firebird with 700. I've bren trying to track this rough idle and surging when going into gear. It idles fairly stready but moves around +/- ~60RPM When it's warm and you go into gear it drops to around 450 and shoots up to 600 a couple of times then settles down at low 500's
Just cleaned the IAC and it helped slightly. Also checked for vacuum leaks but haven't found any although when you touch the gas just a hair there is a whistle sound somewhere from the engine. Push the peddle a little farther and it's gone. Anything I should look for in a data log? I have EBL and a aldl cabl

I should mention its idling lower than what it's set for in the bin but not by too much.
Been out there all night so bed here I come!!

 

> gas just a hair there is a whistle sound somewhere from the engine.

It is usually the gasket between the TBI unit and intake manifold that causes this. They dry out and start to leak.

RBob.

 

mine is doing something similar but I found my iac plug is damaged. please post what you come up with to fix it in case my new iac plug doesn't fix it.

 

I will update if I find the problem.
Didnt know the car had a vacuum ball under the fender! Found a couple leaks from that, doesn't seem to make much difference :/

Ordering a new gasket for the Tbi soon. Do you think that'll cause the going into gear problem? It doesnt seem to do it when it's idling higher.

​​​​​​​Found an exhaust leak at the front clamp on the hollowed cat, may be one father up but having trouble finding one if there is.

 

new tbi gasket on, old one was as hard as plastic but not sure if it leaked from how it looks. idles smoother maybe? Doesn't surge when going into gear while cold now but does when somewhat warm and up. It does in in CL & OL.

Still hear a whistle when barely on the gas. Maybe the iac valve is bad?

 

I suspect it to be this Gasket Would that cause problems?
Okay I found the whistle!! Haven't fixed it yet though. It's the top gasket on the injector pod setup thing.

 

Just replaced it, didn't help. Ordered a tb rebuild kit to see if that helps. The whistle was coming from right where that gasket was, maybe the fpr.

 

old cars man. always something.

 

I was gonna say that that is a fuel passage, so wouldn't be the cause of the whistle. At least replacing the base gasket made the engine run better, so at least it was leaking.

As for the whistle when just on the throttle, is the throttle open enough for the IAC to start to open? Can use the WUD to see this. Can also use a piece of hose stuck in your ear to pin point where the whistle is coming from.

RBob.

 

The throttle body is currently off for the rebuild so I can't test that yet, I did do the hose the other day. The whistle was loudest around the fpr diaphragm gasket but I don't notice any fuel coming out.

Now that I am thinking about it the iac steps only moved 1 when the whistle occurred. Still at 0% tps

 

What is a "stall saver"?

 

It's in the EBL flash bins, may be in stock bins as well. It raises the rpm when it gets to low and stops after a certain rpm ex. Enter:400 Exit:550

 

Rebuilt tbi. Runs better but whistle still there along with one surge or two going into gear. Going from reverse to drive or drive to reverse doesn't do it. Might try raising the idle rpm by 100

 

Look for a lean area in the VE table that is being hit. Being lean is typically what causes an idle surge.

RBob.

 

Will do! Haven't gotten a fuel pressure tester yet but I've seen that red fpr springs are 18psi and the one in mine looked dark red. I do really need to test fp tho.

Hesitation for a second when first pushing the gas where it kind of bogs before picking up. Only does it cold. Probably changing the fuel filter just to rule that out.

 

I have the upper left triangle of the ve table set to 57.65 and get pretty good blm and int at idle. At hot idle I noticed iac steps are 1? While idling in drive it's 25.

 

Problem solved with more tuning and maintenance

 

this thread has been all over. will you post a quick list of the things tuning wise that you believe solved this issue?

 

Looks like it was solved with lower ve changes.

 

What are lower ve changes? My car is doing the same thing. When the car is at operating temperature and stops at a light, the idle drops and the car wants to stall. Once I start going it runs fine.