PLEASE HELP !!
My 97 Ram 4x4 with a 5.9 runs like crap until the engine comes up to operating temperature. It backfires, midfires, dies, won't idle, etc. As soon as it gets warmed up it smoothes right out. At first I had a code indicating the IAC was faulty, so I replaced it,,, no change. Since then I have replaced all these:
IAT MAP, TPS, Cam Sensor, Crank Sensor, Dist. Cap, Rotor, Plugs, Wires, Coolant Sensor, IAC (again), Fuel Pump and Regulator.

I have good cosistant fuel pressure. I have re-outed the plug wires per the TSB.

My understanding is that this is occuring in "open loop" mode. I have a service manual and looked up all the sensors that are affected during this mode and have replaced them all. I do not suspect the Oxygen Sensors since they are ignored during Open Loop.

Can someone please help point me where to go next? What else would cause my truck to run so bad while in open loop?

 

Hey winginged,

I have a 97 5.9 and had a very similar problem. This may or may not lead you to something you havent tried yet.

I had replaced all the same items, and would still get a CEL for #5 cylinder missfire. Only my problem got persistently worse over about a 3-4 month period. My long story short is that I did a compression test, and found that #5 was very much lower than the other 7 cylinders.

I yanked the heads off and found that the #5 exhaust valve was bent... I replaced the heads, and for the first few miles the truck ran like new. I took it on a longer road trip to break things in, and I started having multiple cylinder missfires, low power, high heat, etc.. I thought I melted something down already!

The long story short, the second issue was brought on by a plugged/rattling catalytic converter. I think by having a bent valve for a while like I did I was creating some extra-high exhaust gas temps and it caused the CAT issues.

So, go to Autozone and rent a compression tester if you dont have one.. might check to see if you have a cracked head/bent valve. I've read numerous threads in this forum about the magnum heads cracking, etc.

Good luck!

 

also, check the heater circuit for your o2's... I had a blown fuse on one of mine and it ran similar to yours but off & on warm or cold... worth a look.

 

compression test
o2 sensors
bad PCM

 

sounds like a bad catylitic converter take out you o2 sensors and start it if it runs better your cats out. I had the same problem on my 99.

 

Damn, you sure spent a lot of money swapping parts rather than diagnosing the problem. Get your cat pressure tested.

 

Since Gary showed up... made me think, didnt you have a similar problem because your fuel sync was off when you did your rebuild? if he swapped the cam sensor, his fuel sync could be off

 

I had an issue with the cam sensor being off, that is correct. I had a booger of a time aligning the rotor bug with the #1 Cylinder mark on the cam sensor. But once I got it done, never a problem again. Well, I say that, but there are times when I attempt to start the truck and it fails to catch, so it may need to be adjusted ever so slightly.

BTW Steve, my freaking oil leak is getting BAD. I have to replace that rear main while at the same time rebuild the transmission. My truck is slinging oil like a Texas Wildcatter and she goes through gas like a sailor goes through booze on shore leave. Last weekend I was hauling some Beetles to Tulsa on my trailer and was barely eeking 10mpg. My baby is sick, so she's going on the Injured Reserve list soon.

 

wow that sucks... my '05 is pretty much parked... your probably not aware but I'm commuting 170 mi/day and the ram was killing me in the fuel bill. traded in a '00 QC 4x4 dak towards a '01 vw jetta 1.8t and couldnt be happier... thing is a little screamer for the most part (still stock)... cant wait to put the "steve" touch to it lol will be shooting for 240~250 whp when all is said & done. 300 whp is not unrealistic but not in my future... (live in smog restricted CA)

 

Head over to http://www.vwvortex.com for Jetta mods.