My truck recently started to not want to start. This problem started about three months ago with having to restart the motor after dying immediatly after starting.now the problem has progressed to this.....When I start the motor it will run for about three seconds then die. If I give it gas , it will continue to run. I can drive it but I have to constantly give it gas or It will die.This does not happen every time I start it, but it is getting to the point where I am thinking that it will not be long before it does.(not stay running every time I start it.)I have changed the fuel filter,checked the fuses and relays.I am starting to think that it may be a sensor problem.MAF sensor....oxygen sensor....ect. any and all opinions and/or help will be greatly valued. Thank you for your time.

 

If the Idle Air Controller isn't working, giving it a little gas makes everything normal. The general consensus seems to be replace the IAC, although some IAC problems are caused by the TPS. IAC is a pretty safe bet.

If giving it some gas will keep it running but it's way down on power, it could be a plugged exhaust.

 

I have fairly new cat back duals...I also have an oiled k&n filter..could it be the oil fouling the mass air flow sensor?

 

Yes, maybe. Your engine goes through three phases of fuel control when you start it. On initial startup, the ECT (coolant temperature) is what determines how much fuel to inject. This lasts for a second or two. Then the MAF takes over for the next few minutes. The computer reads the MAF to determine how much air is flowing and injects the amount of fuel to correspond to that amount of air. After a few minutes, when the O2 sensors warm up, the computer ignores the MAF and adjusts the fuel based on the O2 sensors. Recapping, ECT for a few seconds, MAF for a few minutes, and O2 sensors after warmed up.

So yes, it is possible that the cold start injection is starting the truck and it dies when the MAF takes over. The MAF wouldn't be dead if oil fouled, just read too little flow. The question is, after the truck warms up, when it isn't using the MAF, does it idle OK? If so, I'd agree that the MAF could be the factor.

I still like the IAC theory at least as well. There are posts, you can search them, for cleaning the MAF. It isn't hard, you don't even need a tool to get to it. Worth a try. As to the plugged exhaust, I assume you meant the exhaust from just behind the cats to the bumper. A plugged cat can still allow the classic starts won't run symptom. You can remove the O2 sensors in front of the cat. If it will run then but not with them installed, you have a plugged exhaust. Don't run with them out, just a 1 minute test.

Good luck.