BTW check 02 sensor. At high speeds it could be feeding your truck to much gas thus causing it to misfire.

 

Okay guys, I temp tested the cat today (local shop was closed but found a temp tester). Does this sound like a shot cat?

Input temp = 370 F
Output temp = 518 F

I did this with the truck in park, idling, after driving it for about 20 mins letting it reach operating temp. Found the temp immediately before the cat and immediately after.

-Dan

 

Anyone? Don't mean to be antsy, just want to get this figured out before Tues.

Thanks,
-Dan

 

my problem was the map sensor. started just going up hills then kept geting worse. check out my post "knock sensor"

 

Could be the wires, although you're right, that would be weird doing it after all this time, now that I think about it.

The cat looks normal from the temps you gave.

I would have the shop test it out.

 

Let us know what the problem is because mine is doing the same thing. It does it in every gear (manual) and when trying to hold the RPMs between 1200 and 2500. It doesnt do it while not driving though when I hold it in those RPMs. Thought it was the TPS and changed that, wasted $50. It doesnt do it when being given gas or on deceleration, only when being somewhat held at the same speed in those RPM ranges, like going downhill on cruise control is the worst.

 

It also doesnt do it while the engine is still cold...the first 5 minutes of a drive are silky smooth but once it warms up, it's annoying

 

Possibly a Bad fuel pump or going bad.

On these trucks ive done fuel pressure tests that read normal, while the customer has complained of the truck just missfiring for a few weeks, then to just dying out

also you can try looking at the coil

 

Or the CPS. Classic CPS prob after warm up.

 

Everyone,

Sorry for the late reply, didn't keep up with the thread. I think you were right jason.w. Arranged the spark plug wires according to the TSB almost two weeks ago and no more problems to report!

Thanks to everyone for their ideas, I appreciate the help. Saved me some money from the shop

Caseys500: Definately worth a shot to try, only costs you about thirty minutes of your time.

Going to VT tomorrow, will be driving about 600 miles. Updates when I get back.

-Dan