Have had what feels like a bad miss for about 3 years now that nobody can seem to figure out. 2001 4.7 4x4 Most noticeable when first driven after the truck sits overnight and seems to go away after about a half hour or so of driving. Much worse in the cold weather and operating temp doesn't seem to make a difference. Idle is always perfect. Every once in a great while it will act like its down a couple cyl on acceleration. Can mash the pedal, it boggs down and just creeps along then jumps back to normal and takes off. Holding a steady speed around 55 or so the truck will jerk fiercely. Had to replace u joints because of it. NEVER thrown a light or code!! fuel pressure checked ok, transmission checked ok, replaced plugs, cam & crank sensors, PCM, & TCM per dodge dealers. All modules have been updated. If anyone has come across something like this any advise would be greatly appreciated.

 

What type of plugs did you use? (Durangos don't like platinums). Did you also replace the cap, rotor and wires?

 

4.7 doesn't have cap, rotor, or wires. Like samnbensdad said, what plugs do you have in it, and hopefully you have replaced the plugs in the past 3 years! Since it does it more when it's cold, I'm willing to bet the gap is too large at this point due to it being fouled.

I'd do a fuel pressure test, because if the injectors aren't getting enough fuel and are being starved, it makes the engine run rough. I'd go ahead and replace the plugs with Champion Copper (el cheapo from your favorite parts store) and don't use anything other than copper core. Gap the plugs to .040, don't trust the box if it says pre-gapped to ____, more often than not you have to gap them yourself the old fashion way anyways.

Like samnbensdad said also, the Durango does NOT, I repeat NOT like Platinum plugs and if that is what is in the engine now, there is your problem. They cause all sorts of problems from blowing a CAT due to running rich, to like your problem is running rough.

That leads me to my next subject, make sure there is minimal back pressure pre-CAT in the exhaust. This can cause backfiring and knocking due to exhaust inadequite flow from the CAT convertor.

First off check those plugs. I added a link below to go by in case you don't know how to read spark plugs.

https://dodgeforum.com/forum/1st-gen...ml#post2030778

 

Oops, I guess I missed the 4.7...

 

Could be an IAC or TPS. You should at least clean the Throttle Body and replace the spark plugs as Widow stated.

 

I've always been convinced it was spark so I'm on the 4th set of plugs. Yes they are the correct ones gapped .040 and they look perfect. It's definately not TPS. Had that go bad before so it's new. Can one of the coils act up and not throw a code? Or maybe cat converter?

 

Yes when the CAT goes it doesn't normally throw a code. If it does it would be like a P0138 or something like that but normally if it's clogged it won't have a MIL.

Get that back pressure check and the pressure will tell you if your CAT is okay or dead.

Also the coil packs don't normally go out but that could lead to your missfire. I'd take it to a mechanic or the dealer (I'd prefer mechanic less likely to get ripped off) and have them test the coil packs.

 

Honestly I'm about fed up with dealers. Everything they've suggested is a mere guess diagnosis wasting a lot of time & money. Can back pressure test be something I can do at home? Also what is IAC? Throttle body is clean

 

The IAC is the Idle Air Control valve that regulates the air flow to the engine during idle. It's got a plunger on the end and located at the back of the TB.

Usually a back pressure test can be available at a local muffler shop and they will do it for free more than likely. If not it's only like $20 or so. It requires a gauge that most people don't have laying around the shop.

 

Thanks WW. Looks like I'm headin to the muffle shop