I have 99 Durango with a 5.9 V8 and 4x4. It started suddenly chugging and stalling and with full throttle, only giving me between 200-400 RPM. At this point she'll either stall and act flooded, or she'll power through the mess and start driving again. Sometimes immediately, sometimes after 20 mins. Then she'll run smooth as butter for 10-20 mins and start dying all over again.

I have already removed and completely cleaned the throttle body spotless and replaced gaskets. I cleaned the IAC and MAP with CRC electronic parts cleaner and replaced the TPS. Plenum gasket appears fine and no loss of vacuum pressure in the system. Fuel pump is sending pressure fine and the plugs and wires are all fine and have been replaced recently. I replaced the TPS valve and hose (looked half dead and is a $2 part).

The truck is currently at a repair shop and they're completely stumped. They've spoken with 3 other shops and even Google their a$$ off trying to figure it out. The only thing I haven't heard from the shop about yet is the condition of my CAT and the O2 sensors. Should find out tomorrow. The only codes have been occasional misfires from random valves.

Ideas I'm guessing @ so far:
O2 sensors (pre and post CAT)
CAT
Timing chain
Cap/rotor/coil
Crankshaft Position Sensor

PLEASE HELP! So far the repair shops have been stumped and I'm a disabled vet and father of 3 that makes a living making and selling jewelry. The durango is my family's ONLY vehicle and we need her NOW to get to craft fairs and car shows this summer! Any thoughts would be greatly appreciated everyone!

 

ignition module could be bad (easy enough to test), computer could be getting wonky (harder to test) cats typically don't come and go, crank sensor is another possibility, and the shop should be able to test that, timing chain doesn't fail often, and would jump timing so issue would be more consistent I would think.

 

I hear tell that there is a possible ECM update I may need and I agree with you on the timing chain, if it was over stretched or a tooth busted off or something like that, wouldn't it be a consistent issue? The same is my opinion for the catalytic converter, if it's clogged then why is the issue coming and going? Looks like the ignition system is my next stop! Thanks for the advice! I'll post an update this afternoon with today's troubleshooting results.

 

UPDATE
Talked to the shop and they're determined to have the problem identified today but they've been forced to test every damn sensor and plug and wire in the ignition, intake and exhaust one at a time. Hopefully I'll have good news coming soon. But please don't be afraid to toss suggestions at me. Stumped 6 mechanics so far and counting lol

 

not sure if durangos have it but the coolant temp sensor is bad. I say that because I had a saturn that did the exact same thing and I checked the same things and then found a tip about it buried in google.

edit
also, if you replaced the iac make sure the plunger is set correctly. the one I bought new was not set correctly. I just decided to check before I put it in and it was wrong out of the box thus giving indication that iac was not the problem when in fact it was the problem.

 

So we finally got her fixed! About a dozen mechanics and 3 shops later we got our answer. A partially burned out ECM. It had suffered heat damage in the past and was fading in and out. No codes or anything of course. So Roxy is back and badder than ever! Thank you to everyone that lended a hand figuring this out. This truck is our money maker this time of year

 

Moved to correct section.
FF