Hey all,

Truck is having a hard time on the highway. For the past couple days, when driving above 70, every now and again the truck almost feels like it misfires for a second then gets right back up. In a 50 mile trip (all highway) it did it three times. So yesterday I only drive 65, not a problem (she did it once when I got up to 70). Today she did it three times at just 55. Tested and does this with O/D on or off. City driving is fine, truck runs and shifts wonderfully.

Any ideas as to what this could be? Possibly related to the TC or the flexplate?

Four days ago replaced the TPS.
About two weeks ago had a shop bend the transmission dust shield back (it was hitting the flexplate when going 65), new tie-rod end
Plugs, wires, cap and rotor (brass), and U-joints for rear driveshaft done about three mos ago.

99 1500 318 4x4 QC Auto, 124,xxx miles (around 50,000 on the tranny)

Thanks all,
-Dan

 

Did you have a CEL Light?

 

I know this doesn't help you at all, but my truck does/did the same thing. Just only my CEL would flash, and not stay on. I would just get outa the gas and slow down. Always scared me so when it started happening i would slow down and stay slowed down. Happened at the same mph. I changed plugs the other day and it hasn't done it since. Guess we will see what happens when i have 2 snowmobiles behind her.

 

Try spark plug wires.

 

Isnt a flahing CEL a missfire.. which means all that un burnt gas is getting pushed into your cat.

 

I had same problem, put new whole exhaust system on, headers, cat, and muffler. problem went away... I think my cat was bad so that could be your problem... mine started same as yours but slowly worked its way worse till it would misfire even when idleing... I would try new cat and even if it isnt the problem your not out a fortune and ur truck will run better

 

That is also true, check your cat

 

No CEL: Going to Autozone tomorrow to have them scan for any codes
Cat's good: Banged on it with a rubber mallet, no rattling
Wires should be good: Replaced three months ago - I would test them if anyone has a method
Plugs should be good: I'll pull them tomorrow and have a look

Called the local shop today and they don't know off the top of their head. Dropping it off Tues to get a diagnosis.

Any other ideas?

Thanks for the help everyone! It's winter and the sleds gotta get up north for SNOW
-Dan

 

Just because the cat isn't rattling doesn't mean it is good. Just means that its probably good. If the wires and everything else test out OK, get it checked. A shop should be able to do that.

Take a multimeter and measure the resistance of each wire, from the spark plug boot end to the distributor cap end. If one of them is way higher than the others, there's probably your culprit. When you replaced the wires, did you route the wires exactly as they were before? Chrysler has a very specific routing procedure for the wires, and if they aren't routed right, it could cause intermittent misfires ("cross fires").

TSB 18-48-98

I doubt its the plugs, but yeah, take a look.

My gut tells me its the wire routing or a broken wire. Hopefully its that simple.

 

jason.w

Can the truck exhibit these problems three months after I replaced the wires? Truck fired perfect before this crap started. It seems like an awful long time before this problem arose, but then again, stranger things have happened.

I never routed the wires in a specific mannor to begin with, so I will re-route according to the TSB specs. Could the wires be bad already? FWIW, the wires are cheapo Pep Boys brand ($30 set I belive).

I'll head to the local muffler shop tomorrow also and have them temp test the cat.

Thanks again,
-Dan