A few months back my car(91 fbird LO3) started giving me trouble. It would stall and be very hard to start. Well, I took it to a family mechanic and he said it was the IAC valve so he changed it and it has been running great; good idle, no problems starting. Today though, I stop at a friend's house but he wasn't there. I go to start my car and it fires up but then dies immediately. So I turn the key again and nothing, just makes that cranking sound. I hold my foot on the gas pedal then try starting it while holding giving it gas. It struggles but starts and runs like crap. RPM's all over the place, sputtering, and when I try to rev the engine it doesn't work so it dies out again. Well, I open the hood and take the lid off the air cleaner. There was some sort of smoke coming from the throttle bodies. I have no idea what that could be. Well, in a last effort, I get in my car turn the key with the gas pedal held down and it starts. There was black smoke coming out of my tailpipes, but after I reved it up for a while it stopped. The idle I noticed was much higher than it usually is. These are the same exact symptoms that it had before. Could it be the IAC valve again? One other thing I noticed was that when the hood was up and I had the lid off the air cleaner, there was a loud hissing noise while the engine was running. I am not anywhere close to a car guy, but I do know the different parts and functions. If anybody can lead me in a general direction I would appreciate it greatly. Thanks.

 

The lound hissing sound is could be a vacuum leak somewhere, which could make starting difficult. You probably ended up flooding the engine that way too. When you crank the engine with the gas pedal floored it goes into "clear flood" mode allowing the excess gas to go out the pipes, which when it finally fired accounts for the black smoke. With the engine running try to pinpoint where the hissing is coming from. A little bit of hissing is normal form the TBI at idle, but it might be a split or disconnected vacuum line.

 

Thanks for the advise andy. But how do check for a vacuum leak. Will you feel air coming out of a line or something like that?

 

You WILL NOT feel air coming out of a vacuum line. You WOULD hear it going into a vacuum line.

You'll have to listen for a vacuum leak, and thoroughly examine each line for cracks holes, or maybe being disconected.

Yes, the black smoke is all the excess gas you just flooded into the engine. Usually on fuel injected cars you dont touch the gas pedal at all. Maybe just press it to the floor and let up while the key is on then try to start it. Holding it to the floor on any motor while cranking should usually be a last resort.

Was it black smoke coming out of the throttle bores or was it white steam?

 

Also bottom line, (since you say you're not a car guy.)

An engine needs three things to start/run.

1. Fuel (Relatively close the correct amount)
2. Air (Agian, not too much or too little)
3. Spark (Good Spark)

For one reason or another one of these was wrong or not present.

This is a generalization, there are of course other factors that effect our now so computerized cars to start/run. But these are always the things to first look for.

 

Don't get me wrong, I know a fair amount about cars, lol, but I'm no expert. I know that in fuel injected models you shouldn't use the gas pedal but that is the ONLY way that it will start. I will check out the vacuum lines when I have a chance. Oh, one last thing, the car will sometimes die out when I come to a red light or stop sign.

 

Check for an injector being clogged.
I've had that problem before and that was the cause.
Come to think of it, all of your symptoms seem to point to that a little.
You fix the problem of not enough fuel when you push the gas down, BUT then you give it to much air.
Get some cleaner then drive around for a while.