Ok, I have a 92 Camaro RS 305 TBI....I have changed the PCV Valve and filter, changed the oil, changed the fuel filter and air filter and thats it for right now. Here is my problem STILL: Start engine in the morning and let it warm up (idles up to 1500 then back down to around 600 until you put into drive then its 500) then I head off to work. Everything is fine till i get to about the 2nd or 3rd red light....i sit there waiting and when it turns green and i push the gas pedal...it seems to cough (hesitate) and then slowly but surely it gains momentum....but only gets worse down the road. This morning at about the 6th or 7th red light....it shook the car and the rpms varied from 750 to almost stalling under 500 and then back up again, and this time when i pushed the gas it died....so i pulled over to the side of the road and let it set there for 5 minutes exactly. It started up, but you could still here it hesitate and you could smell the gas....i put it into drive and it died instantly. Well, I tried this over and over and finally decided to call my wife to come get me to take me to work. 10 hrs later I come back to the car and it starts up just fine....drive it back home and it hesitated once at one red light, but nothing like it did on the drive to work this morning. I thought it was the fuel filter, but i was dead wrong. I checked all the hoses (lines) from the tbi I could and they all were fine (no cracks or leaks). I just dont know what to do next? The Check Engine light never came on....but it did come on about a month or so ago on a long interstate drive (about 100 miles). After i pulled over to get some gas and check the oil and got back in....it didnt come back on....so i never thought anything else about it. Anyone got any ideas? I was thinking maybe either injectors clogged, or fuel pump or i heard you all talking about IAC (dont know what that is or what to do about that) maybe O2 sensor? There could be so many different things. Would love and appreciate any and all comments for this under knowledged amateur. Thanks!:hail:

 

I had something similar happen to me a while ago. My car would idle rough and would never quite run right for about a week or so. Finally the problem was revealed when the car up and died one day. It was the alternator, it wasn't producing enough power to run the car correctly. As power wasn't sustained, the car didn't know wheather to run as a TBI or carb and kept doing all kinds of rude crap. Might not be the same problem here, but worth looking into.

 

The check engine light probly came on because of a fault the computer picked up but if it didnt come back on then it was just something the computer didnt like and wasnt a serious fault.
It could be the Iac valve, idle air control valve, it's fairly cheap to replace or you could just clean the old one with some carb cleaner, check you sparkplug wires and your vacum lines if there in good shape then just try raising your throtle to around 700 to 800rpm at idle.
chris

 

I had the same problem. I also have the same car. 1991 TBI 305. Anyway, turns out, it was the fuel pump. The thing just went out. Your idle goes up, and down, up and down. When you accelerate, it will lunge, or it seems as if you have to floor it for it to move. Definitely a fuel pump. I brought it in, and they had to drop the exhaust, drop the tank, and install a new fuel pump. I hope this helps.

 

That's a definite possibility. I had a TBI with a failing fuel pump. The engine would run a little lean at startup, then way rich as soon as it achieved closed-loop. My speculation is that the ECM used the BLM tables when in open loop, so it was too lean. When it hit closed loop, the O² wasn't satisfied and the ECM went full rich to compensate for the low fuel pressure.

Test the fuel pressure. You should be seeing 11-13 PSIG. You'll probably have to install an adapter to test pressure, since GM cleverly omitted the test fitting on TBI setups.


Just to be sure, you should also clean the throttle body, idle air passages, and remove and clean/lube the IAC stepper motor if cleaning the TB doesn't solve the problem.



And for argument's sake, if the oxygen sensor hasn't been replaced in the last 30,000 miles, it's time.

 

Ok thank you so much everyone for all your input....and of course thank you so much Vader for all your wisdom as well....you always seem to have such a great explanation for everything. Im going to go out first and test the codes off the ECM by using the paper clip method I saw on here. Then see what that tells me. I have looked in the book and I never saw a code for the IAC, but Im going to clean it anyway. I have already cleaned the TBI and the air passages and that didnt help me any at all with the problem. You know I really seem to think it is something to do with the fuel. The other day when it died on me at a red light....i could never get it to start back up again...smelled fuel like it was flooding itself to death....so i left it in the parking lot and came back after work (about 9 hrs) and it started right up and I drove it home with no problems. But here it is Sunday....it hasnt been started or driven since Friday now and I know its going to do the exact same thing it always does....it will start and idle and seem fine....until I drive it down the road and hit about the 3rd red light and sit there for a minute....then as soon as i hit the gas....it will bog down and spudder.....and never recover until I let it sit again (ie: work) or die at a red light. Anyway....time to go out and see what I come up with....i really dont want it to be the fuel pump, but oh well....cant always want everything to be perfect with your car at all times. Thanks again everyone for all your knowledge.

 

Well I have done a little work now.....tested the ECM for codes and I got the dreaded Code 32. So of course i look it up and it says EGR System.....so i went ahead and removed the EGR Valve and according to my Haynes Manual...it (the diaphram) seems to move with moderate pressure like it should. So Im wondering now what could it be....maybe the EGR solenoid? I was going to go ahead and remove and clean/lube the IAC, but it seems as if I dont have a big enough wrench to take it off with (gee I didnt know it was that big!) But anyways....what does everyone think? Should I go ahead and spend 50 bucks to replace the EGR thinking that would make my problem solved or should I go ahead and get a wrench and take the IAC out and either clean it or get a new one and install the new one. The EGR valve looked good and like I said moved freely with moderate pressure....the gasket looked good....the hose that went to to the top of it looked good and their is air coming out of the port on top when you push on the diaphram....just wondering which route I should go before i spend more money on something that wont fix my problem. Thanks again in advance for any help!

 

I just bought me a wrench and pulled the IAC valve out.....and I think this actually may be the problem. I cant even move the thing....i mean i measured it so i could see if it was 1 1/8" like the specs say, but you cant even move the thing or twist it....its the type that has the collar so your supposed to be able to move it to make it that length....and you cant. So I think Im just going to go out and buy me an IAC Valve (28 bucks) and replace that and put my EGR back on and see what happens. Let me know if you all think any differently.

 

I finally figured the IAC problem out (like i said before Im not a mechanic by any means) but I saw in some posts that you can move it back and forth....anyway.....i took it out....saw an earlier post by you Vader about cleaning it.....and well I thought about cleaning it, but i thought well I have the money right now why not just go out and buy a new one...it was only 28 bucks so why not....seems like it would be worth it....anyway....installed it to its proper 1 1/8" setting....put everything back to its original status...let it warm up (it sounded really good at first) and drove to the gas station to fill it up. I had read that you should run it at 40mph for a little bit to let the ECM reprogram or something so I did that....and sure enough....next red light.....sat there and sat there and when it turned green.......HESITATION (its almost like it coughs and then goes but still stutters as it goes). When I got back home I thought what the hell lemme try some carb spray....of course that didnt help...but anyway....any suggestions from anyone would be great....I think my next step is going to be to take it to the shop, cause I really dont know what else to do other than EGR (although it looked good when i took it out). Thanks again.