I just traded for this.It is a 91 Camaro 305 TBI.When I got the guy he said there was a sensor needing replaced.So I replaced the coolant temp sensor on front of manifold.No change.I forgot the problem when it starts it will run for a few seconds then dies.Then if I restart it it will idle up and down and then die.It will eventually idle if you can keep it running long enough.So finally I reset the timing it was way advanced I set it down to 0 with the wire unplugged.I also replaced the idle air control valve,I bought a map sensor hooked it up with no difference so I am taking it back.The egr seems to be fine.So I dont know what else to try.Maybe the fuel filter.I was wondering if the TPS would cause this also?I was able to drive it over the weekend but was real disappointed I know its a 305 but no power at all.I also found a burnt plug wire and replaced it.Any suggestions are much appreciated.I have been going thru pages of post but can't find the exact problem.Thanks in advance.

Sorry could someone move this to tech.

Welcome to TGO

There are couple of tests that you should perform.

A very common problem that plaques 'vintage' 3rd gens is a low fuel pressure. 9 out 10 posts with symptoms like you are describing can be traced and eventually attributed to a low fuel pressure. To be certain - get a FP gauge and verify that you have at least 12 PSI. Most Auto parts stores will rent FP gauge set - make sure that this set has GM TBI test fittings - ASK!
Sensors typically are least prone to fail, exception being CTS and MAP. Sensor functionality can be easily verified with a DVM without resorting to replacement.

//RF

Thanks.
This morning I drove it to work.And it would barely move.It did feel like a fuel pressure problem.But would fp make it idle high and low like it does?

'toxic

You need to post as much info as possible - RPM, idle quality, etc. Trying to diagnose a problem across the Internet only on few scant passages can be a load of fun -

At idle the ECM will try to maintain commanded idle RPM by opening IAC a bit more. Larger IAC opening (same as having a larger vacuum leak) will result in idle speed flare-up. ECM will see increased idle speed and will close off IAC a bit - resulting in engine RPM drop. All of this is (possibly) due to low fuel delivery - engine running lean at idle. Since ECM does not know that fuel pressure is low it will attempt to maintain idle speed (this is part of its programmed response loop).

Otherwise, of throttle response is very sluggish - you even may get a pop through the TB.

Check FP before changing anymore parts (and save money)...

//RF

Will do thanks for the info.

check for codes stored in ECU at ALDL link. we assume no CE light lit. I believe if not lit a code may still be stored. I cant imagine car running poorly with no codes.

Yes, low fuel pressure pressure causes the engine to lean out. A lean AFR causes the engine RPM to surge, usually followed by a stall but not always.

Low fuel pressure also causes a lack of power.

RBob.

Thanks for all the input guys I appreciate it.I am going to kick the heat on when I get home and go rent the FP checker.I am going to get a fuel filter also just cause the on there looks pretty old.
Is there a certain mileage that these pumps like to go out.I know late 80s s10 always seemed to go out around 90,000.My car has 108,000?Just curious.

The life of the fuel pump depends upon how well it was treated. Keeping a decent fuel level in the tank and changing the filter on a regular basis is good for the pump.

Running the tank level down can uncover the pump which allows it to run dry. A clogged fuel filter causes the pump to work harder which also shortens it's life.

RBob.

I checked the fuel pressure and at idle it only read around 3-4 psi.Wouldn't even register when I turned the key over had to start it to get it to register.So I changed the filter and no change.So I will be changing the pump this weekend.Thanks for all the help and input again guys..

So guys I installed my new pump last night.Fired it up and idled like a champ and rpmd right up thru the rpm with now hestitation.Thanks again for all the advice..

RBob.

You need to send old RBob some money for a Burger, Fries, and Large Coke.
Know what I mean.

-

Bringing this post up from the dead because I am have some similar issues...
Car starts up and idles great cold, runs great when warm too. But on a re-start after leaving it for say... half hour, RPMs will go up and down a bit then smooth out after a minute of idling. It also shows a lean condition in WOT (Checked with Auto Xray)
Its a TBI/Auto car, 145K, probably stock FP.

Bump-

I recently installed a WBo2 in my car.
Cold start up, runs lean (16-17 AFR) until warm.
Warm start up (after sitting 30min- 1hr) AFR's go all over the place, along with the idle.
Cruising at highway speeds is about right, between 14.6-15.5
WOT is awful lean, sometimes not even getting a reading.
Fuel Pressure at the pump is a little low at 10PSI

Any ideas? THANKS!

Check the fuel pressure under load. Probably dropping like a rock. A quick test is to observe the fuel pressure and wack the throttle open. Can do this at a standstill with the hood up.

If the fuel pressure drops even the slightest then there isn't enough fuel delivery. Clogged fuel filter will also cause this issue.

RBob.

Thanks RBob,
I used a T in the line in place of the fuel filter when I checked it, so I think I can rule out a clogged fuel filter.
I do believe I saw a slight drop in pressure when I stabbed the throttle at idle, went from 10-9PSI in Park.