Hi guys,

I hope you can help me out on this one. My father has a 98 1500 with the 318. Has 140k on it. Truck's had a rough life. Alot of stop & start and heavy pulling.

Here's the problem. When the truck gets warm it starts missing and back firing, and generally running like crap. After a day or two of this, it will throw a code. Something to the effect of 02 sensor high voltage. Sorry can't remember exactly which one.

Things that have been replaced in an effort to fix it:

1. Plenum gasket about 10k miles ago
2. Both O2 sensors
3. Cap, rotor, wires, coil, plugs, Etc......Everything to do with ignition and spark.
4. MAF sensor

We are at our wits end on this. He's be fighting this for about a year and it isn't getting any better.
Anybody want to take a shot at what else it could be? I was thinking about a partially plugged cat, but the truck definately doesn't overheat and the cat doesn't rattle.

Any advise would be appreciated.

 

Others will chime in but I'm going with Temp sensor, IAC (Idle Air Control) Sensor or TPS (Throttle Position Sensor). When you replaced the plenum was their a lot of oil or a little oil in/on the pan? 140k on the cat if its original, about time to replace it or punch out the honeycomb and see what happens.

 

your 98 doesn't have an EGR vavle does it?

i think i'd replace crank position sensor and cam position sensor. do a search on those and see if it turns up any of your symptoms.

 

+1 on IAC

id say r/r the IAC

 

Ok the majority seems to lean towards the IAC. Will this cause the symptoms I described? Not just idle? The truck idles ok. A little "bumpy" but doesn't act as if it wants to stall. I searched and it seems when the IAC goes wacky a truck won't idle right.

Not downing anyone's answers, but we are really tired of throwing parts at this truck without fixing it.


Thanks guys.

 

Before replacing the IAC, pull it off the back of the throttle body and clean it real good, try not to move it much while cleaning it and clean the port it goes into. There's probably a ton of carbon build up in there

 

sorry, but the description of backfiring seems to rule out IAC. iac only bypasses closed throttle plate to maintain idle.

backfiring into the intake is related to timing problems or serious valve problems. its probably not a valve problem or it would do it all the time. timing sensors are crank and cam position, probably cam position.

 

I can't find a CAMshaft sensor in any auto parts store list. Crank position yes, but cam no.

 

Are you still getting that O2 sensor high voltage trouble code after replacing the O2 sensors?

Could it be a partially or mostly clogged catalytic converter? That could cause all sorts of running issues.

 

Oh it has brand new Bosch O2 sensors. Still getting that code. It's what led us to replace them.

The cat, I'm not sure about. It doesn't rattle or overheat. What kind of codes/problems can I expect if I punch out the cat?