Ok guys i posted about this a while ago and never really figured it out, im starting to get desperate, im getting 8 miles to the gallon and ive thrown about 1500 dollars at this trying to fix it. Heres the deal.

The truck runs poorly, has trouble starting when cold, idles rough, smokes unburned fuel when its first started, has a random multiple misfire and the 2 o2 sensor codes. It backfires into the intake when full throttle (sounds like popcorn popping in my air box), shutters at low rpm's once it passes about 22-2300 it smoothes out quite a bit but can still tell there is something wrong, it has no power like taking off up a hill it takes everything it has to make it up. Its getting TERRIBLE gas mileage!

Heres what i have done:

Replaced all 8 coil packs, spark plugs neumerous times, fuel injectors.
Had the fuel pump tested at idle, 1500 rpm, and 4000 rpm
had my cats tested
replcaed all o2 sensors
pulled the front cover to make sure it hadnt jumped a tooth on timing
changed air filter
installed cold air intake
replaced throttle position sensor
intake air temp sensor
bought a reman throttle body
Had all 8 cylinders pressure tested and a pressure hold test for 4 hours on each cylinder, the number 1 cylinder leaked down 3 psi in 4 hours, this truck has always had a misfire on cyl one when the plug starts getting old, ive always replaced it and its fine for months.
I took it to the chrysler dealership, they had it for 4 days and returned it to me and said they couldnt find the problem, they hooked it to their computer and its misfiring on all 8 cylinders just randomly, they said there is no pattern, it just does all different cylinders, they reccomended a new PCM, so i bought a pcm off ebay one of th eones where they program it with your vin, put it in and it still does the same thing. And i dont know what else to try.

A friend said that on the 4.7 he has seen the crankshaft sensor make these trucks run strange, and it kind of makes sense to me because if it doesnt know what position the crank is in that could cause problems. But im tired of throwing money at it and i want some other opinions.

I also forgot to mention when it idles its at about 600 rpm and if your trying to park and you turn the wheel to the lock sometimes it dies but always fires right back up. and also sometimes ill be driving and out of no where it will start runing perfect, usualy for no more than 5-10 minutes and very randomly.

 

Did the dealer do a dry and wet compression test? The 3.7, 4.7 and 5.7 are having valve seat problems on the heads. Causing misfire codes and running like crap too.

 

isnt a wet compression test used to check the rings, and the way you verify what you find in a wet test is with a leakdown test, and ive done a leak down test.

if it were having a valve seat problem it would most likely run bad all the time wouldnt it? it doesnt always run bad, its been doing this for about 40000 miles never got any worse or better other than when its really really cold out side, like we had a couple nights in the freezing numbers a couple months back and when i drove it to work on those morning it never had a problem.

I really dont think its internal but if you think i need to do a wet test ill give it a go. Im to the point i really think its a sensor or something sending mixed signals.

 

The dry test is to see if the compression is low or good, the wet test is to see if there is any change, like the rings. Now you could also do a running compression if you want too. A leak down will help you know if there is a leak getting pass the valves. But the pistons need to be top dead center on each cylinder, to get a correct reading.

 

Pat:

I don't see where you have had your battery load tested? These Durnangos and most other Chrysler vehicles are quite sensitive to a failing battery.

If your battery is more than 4 years old, I would replace it just to rule it out.

Sorry to hear you have spent all those bucks with no positive results. The fact that it does run right now and then makes me think an intermittent ground or harness connection somewhere.

Don