HELP! 5.9L won't stay running ...

Hey guys, looking for some help with this ...

What started as a rough idle has gotten progressively worse - my engine won't stay running now. My check engine light is on, but I forgot to ask the mechanic what code it was throwing. I replaced the PCM because the garage I took my truck to traced it back to that (said 100% sure). Got a reman PCM, made no difference - I think it made things worse, my truck stayed running with the old PCM at least. Took my truck back to the mechanic, he ran a couple more diagnostic tests (not sure exactly what) and decided that I needed a new IAC (again, assured me they were 100% sure). I got a new IAC, put it in and no difference. Now they are stumped I think, and I don't know enough to diagnose what the problem would be. I'm already out $400 in parts that didn't help me, so if somebody could offer any advice on what else to try that would be great!

You can get your codes by doing the key dance. Turn your ignition on off on off on off on and an your odometer it will pop up the code numbers write them down and use that as a starting point. There is a bunch of things that will make it run rough and even not at all. Most popular are clogged cat, cam pos. sensor, check plug wires, or fuel delivery You can check for clogged cat by pulling front o2 sensor and seeing if it will run. cam sensor usually gives a no run situation and no bus in the odometer, check plug wires for crossfire or melting, and make sure your fuel pump is running and your getting fuel and adequate pressure to the rail. That should get you started.

Ok - I didn't know that I'll go give that a try see what I can find myself.

Yeah gonna need the codes.

Also if they were 100% sure and it didn't fix it, shouldn't they have to pay for it?

+1 on getting your money back... if you cant get the key dance to work, Auto Zone will run your code for free. Once you get the code, you will be able to pinpoint it fo sho.

Hey guys, so I did the key dance and it showed P 1685. On a whim I put my old PCM in, and it started right up. Guess the guys sold me a faulty computer? Either way I don't feel I should have to pay for the PCM - wrong diagnosis and a faulty board ....

At any rate, thanks for the input guys!

Glad to hear you figured out what the issue was.