i have a 92 firebird with 305 tbi. ive replaced a long list of parts pretty much everything except the fuel pump/injectors and ive gone through the vacuum lines no leaks reset iac multiple times new ecm everything and it runs great at anything above idle but when i come to a stop the idle just goes up and down almost in rythm doesnt feel like it wants to die it just wont level out. the spray from the injectors seems fine. im thinking it has something to do with the iac step count and/or stall saver which i know nothing about. so im asking what am i gonna need to check that and where exactly should it be? thanks

 

A bad fuel pump can cause the idle issue you described.

 

definitely seems worse this morning, it wont hold steady at all. it does it in drive too at low rpms i noticed(like creeping around a parking lot) when it spikes up it seems like its pulling me then backs off pulling me then backs off. also while it was doing this i could hear a sucking sound coming from around the gear shifter?! any idea what that is?

 

also i ran some carb cleaner thru it this weekend and it seems to be worse now the idle is constantly going up and down wont level out at all im stumped:/

 

I would add a fuel pressure gauge and while under load check for pressure drop. I would have passanger hold the gauge or tape to outside windshield/side window for passanger to witness.

 

a bad fuel pump can cause it to have bad idle but seem ok at anything above that?

thanks for the help by the way.

 

With the SA connector disconnected with use of a a timing light is the idle SA smooth?

spray some carb cleaner or propane at the base TB gasket checking for vac leak there.

 

sorry but whats the SA?

 

spark advance

 

so im checking to see if the idle spark advance is smooth? ok.
the entire spark system is new from the coil to the plugs and everything in between.
heres a list of everythnig ive done or had done:
distributor
cap
rotor
plugs
wires
coil
iac (x2)
tps
manifold temp sensor
o2 sensor
ECM
fuel filter
vacuum lines
timing

theres more too im sure ive been trying to get this thing to idle for a couple months now! reset the iac multiple times, tried it with the stock air cleaner assy. and my open element one, pretty much everything i can think of except the fuel pump and injectors...

 

ALDL provides a link/port to your sensors. you could datalog the event. You will need to buy or construct a cable and download(free) winALDL. It also will show a code.

Key on engine off the CE light blinks then stays on solid?

 

the check engine light isnt on, it was but the codes were for the o2 sensor and the manifold temp sensor, i changed those and light isnt on anymore.

 

I witnessed a situation with bouncy idle, a little less WOT power feeling and random light hesitation under acceleration. The pump was only producing around 7.5 psi on that thirdgen.

 

that actually sounds alot like my situation. ill test the fuel pressure this week, it should be between 9-13 psi correct?

 

good thing the parts for this car are so damn cheap haha i just picked up the tbi base gasket for $2 and i can get the fuel pump for under $30

 

well i pulled the iac out again and it didnt look like it was seating correctly, there was a wear mark on one side of it from where it was seating and nothing on the other side, looked like the pintle was slightly crooked. the part was under warranty so i got a new one and did the install and reset, and it appeared to hold a steady idle! im not gonna count my chickens before they hatch tho lol i did it on my lunch break so the drive home will be the real test, keep your fingers crossed!!! thanks

 

well it didn't work. well I'm pretty sure now that it HAS to be a fuel issue, I've done everything possible with the air and spark, fuel delivery is the only thing left. lemme ask you this....it seems like when I hot rod the car and floor it everywhere, the car will actually idle better, but when I putt around say like in traffic, it doesn't wanna idle at all...is it possible that hotrodding it around builds enough fuel pressure to keep it running? and when driving it like a grandma there's less pressure so it wants to die??? does that sound right to anyone?? thanks all help is greatly appreciated

 

My fuel pump died all at once. but I hear and presume thy can get funky with performance before the final day. How old is it?

I would add the gauge and monitor. should not be all that difficult to do.

 

as far as i know its the one it came with from the factory. well there is an abnormally loud ticking sound coming from the tbi, i can hear it clear in the cab while driving, ive had had 5 cars with tbi and never heard one this loud, maybe injectors/regulator??

 

The 4 LO3 thirdgens I have checked FP had 11.5 psi. Though was probably set at 12.5-13 at the factory.

 

well my cars been at the chevy dealer all day and the damn car wont act up so i cant show him the problem! the problem is definitely intermittent. we tested the fuel pressure when it was acting fine and it was right at 11 psi, but i couldnt test it while it was acting up because its running fine, but i guarantee that on my way home from work itll start idling funny, about 5 times now ive thought the car was fixed but then on my way home from work it starts running like crap again.

 

well guys i know ive said this before but i think i got it figured out lol. ive been running it with no egr for the last 2 days and its been running great.....

 

how stiff should the diaphram on the egr be? i can put my finger in it and its pretty hard to push in and it returns very slowly too.

 

Probably stuck slightly open. Had this problem once. When I was a teenager, I replaced all kinds of parts trying to figure it out but one day, I had the car idling at my high school auto shop class, and my teacher suggested checking the egr. I unplugged the vacuum line and instantly my stumbly idle went smooth. This problem was intermitten but eventually happened at all times. My problem eventually boiled down to a bad egr solenoid. bad fuel pump gave me a similar symptom probably a year later.