I recently replaced my 5.7 hemi in my 2003 dodge ram. Upon initial start up the engine ran pretty rough, then came to idle seeming to be running pretty good. I tried to give it a little gas and it shut off immediately. When I tried to restart it, it would only crank, then it blew the oil cap off. Once more I tried to start and it did the same thing, loud pop, (guessing a backfire??) and a plume of white smoke. Any ideas?? I'm not sure on mileage of the replacement engine, it seemed to be in great shape just from the looks of the internals. Any ideas???

 

you do anything with the PCM?

cou be many variables. start diagnosing such as plug condition and if you getting fuel and if your getting spark, etc

 

i haven't but am wondering if that could be the problem?? It seems to be running the same way it was before it died the first time. However in the process of trying to get it to start It wound up dropping a valve into the cylinder because of a broken valve spring. Now with engine #2 it seems to be running the same way. Is there an easy way to diagnose the PCM or will I have to take it somewhere?? I saw some refurbished PCM's for $150 bucks.. by the time I have it towed and the dealer to look at it I'll easily be out $150, just wondering if I should just go ahead and buy one? Thanks

 

I'd bet it has an issue with the new engine and the pcm not communicating correctly. Probably going to have to take it down and have the dealer do the relearn or something similar.

And even if you buy a new one you will still have to take it to the deaer to have them vin it to your truck I believe.

 

Blew the oil cap off?! Assuming it was on correctly, that's some serious pressure in the crankcase. I don't see how the PCM could have anything to do with that.

 

I agree, blowing an oil cap seems more mechanical based than software driven my sensors or PCM. What year HEMI is this BTW?

 

Its an 03.. haven't had the same issues today. It started up just fine, had a pretty rough idle still, loping alot. Let it run for 3-4 minutes before giving it any gas, when I gave it gas I took it to about 1500 - 2000 rpms and it kinda smoothed out a little. As soon as I let off the gas the engine died then would not restart.

 

What year HEMI and truck did this come out of? Was is a complete drop in engine?

 

the engine came out of an 04.. It was just the rotating assembly.. All accessories were switched from the old engine.

 

Has it thrown any codes with the rought idle?

Next time you get it to start open the airbox and spray ether in, if it idles better then you are lean. If it doesn't help the idle at all you could be rich.

If lean...it starts with the fuel filter, the fuel pump, the injectors....

If rich...it could me lack of spark, not enough air flow, bad timing.