Engine dies immediately when starting

Hi all,

Here's my problem: The car was working fine until this problem occurred - it was sudden. Went to start one day, and it starts right away, then dies the instant that it starts. When I give it gas while starting, I can get it to run for a few seconds, but it is really flaky. If I give it too much gas, it'll backfire sometimes. While giving it gas, the rpm's fluctuate alot, even when I'm holding the gas pedal somewhat steady. It's super hard to keep it at a certain rpm level. I cannot get the car to run ever since a couple of days ago when this problem occurred. The fuel pump does work when I turn the key to the "on" position. Any thoughts?

I'm guessing it could be any one of the following issues, could somebody make a recommendation as to what they think it is or isn't?

throttle position sensor
mass air flow sensor
fuel pump
fuel pump relay
fuel pressure regulator
crankshaft position sensor
ecm

Whatever it is, remember the problem happened suddenly.

Thank you!

Check the fuel pump relay first. It could be causing an intermittant fuel pump. The next item would be ignition module under the coil they can go bad and allow the engine to start but not run well. The next item would be the CPS. Try this and repost to see if it helps.

I'll check the fuel pump relay. Do you have any suggestions as to how to check it?

Do you know how to check the spark for the ignition module?

OK, now I know it's not fuel related - everything checks out fine. I know it's not the fuel pump relay. It's probably the Crankshaft pos. sensor or the Ignition control module. I'll have to check them out.

I switch the ignition control module out with a different one, and the problem remains, so I know it's not the ignition control module. Must be the CPS. Any other thoughts?

Not really. If the CPS doesn't work there are only two other things I can think of besides the ECM. First, do you have a security system. If you do and the light is on this could be causing all your problems and would require a different method of correction. If no security system the other possibility is a bad ground somewhere that is causing the ignition system to lose voltage but that is a long shot.

Maybe a MAJOR vacuum leak - like the line to the brake booster? After replacing spark plugs, I forgot to reconnect that line (I had moved it for ease of access) and it sounded similar to what you have going on.

Thanks, I'll check the vacuum lines. I replaced the crankshaft pos. sensor & swapped a computer from another car, and problem remains, so it must be a bad ground or a vacuum leak.

I figure you have probably already replaced the fuel filter, since you are talking about the fuel pump now. I had an 88 Bonne that did a similar thing with a clogged fuel filter--and it was sudden. A month later the fuel pump went out...? Note--there is suddenly a lot of crappy gas out there AND people are letting their tanks get lower and lower trying to limp to the nearby cheapest gas station, inviting ingestion of tank sediment. I predict more folks will have filter problems soon.

when you say everything checks out in the fuel system, did you check the fuel pressure? A fuel pump can operate, but not produce sufficient pressure, which will cause the symptoms you describe. You should have a minumum of 31-35psi depending on what year the car is it could be higher.

Yep, I checked the fuel pressure - around 42 psi, right where it should be. I know It's not fuel related. It's timing-related (probably), since the vacuum operated systems such as power brakes don't work hardly at all anymore. Something is way out of sync.