Started acting up this weekend on a 400 km road trip. On highway I noticed a slight miss. When I came to a stop in a town the truck stalled. It fired right back up but wouldn't idle. It would run though if I tickled the throttle with the gas pedal. I reached my destination and the truck sat for a couple days.

On the return trip, the truck ran great, no symptoms at all. This morning at home, the truck would start but no idle unless I helped it along.

I know the cat is bad, could this be what is causing this or do I start looking elsewhere?

 

most likely IAC or TPS. also weak battery can also cause them to not idle.

if the idle port or the pintle of the IAC is clogged, a cleaning might help. otherwise replace it. don't push, pull, or twist the pintle. w/air filter removed, you can see the iac opening/closing (or not) to maintain idle.

somethimes the tps will throw a code for high or low voltage, sometimes not.

 

I had that same problem recently. Turned out to be a failing crank sensor. But I'd do what DHV suggested first and clean the TB and IAC sensor.

 

Awesome, thanks guys. The battery was new in the spring so I can rule that out. I'll check it out the IAC, errrr, what product is best for cleaning?

 

carb cleaner works fine.

 

remove IAC and check the well, the port at the end of the well, and the pintle itself. carb cleaner, throttle body cleaner, or brake cleaner (in modest amounts and not into the IAC motor) will work. make sure the port is open and there are no solid chunks of stuff interfering with the pintle.

with air filter removed, observe iac. replace it if its not working right. its about $40-50 at local parts stores.

sometimes they won't idle because the tps is messed up, telling the pcm your foot is still in the gas and it doesn't have to idle. in cases like that its not the iac's fault. hopefully it'll throw a tps related code when this happens. otherwise its hard to figure out (unless you get pissed off and replace them both)

 

Hey, just because the battery is new does not neccesarily rule it out. Make sure your Alternator is chargin then rule it out. After that I would investigate The Idle Air Control motor. My battery suddenly dies on me one day even though it had been cranking fine. Truck wouldn't idle after it died but would run past idle. I swapped a good battery in to see if it would even crank and it soon after idled perfectly. Good luck with it!