I have a 2005 1500 with the 4.7, about 200,000 miles. I've had and intermittent, random high idle. IAC has about 20k miles on it. New TPS. New PVC valve and hose. New intake gaskets. New throttle body gasket. New injector orings. It still randomly does it.

I took it to one shop, and hes the one that recommended the pcv hose and intake gaskets. He said with the code it has that most of the time that's it. He showed me what his database said. I replaced those and it's still doing the high idle at times. It can go days without doing it. He knows the engine is tired, burns about a quart of oil in 6 to 700 miles. He said use good oil and keep driving it.

Once I replaced everything and noticed it was still randomly getting the high idle I went to a nearby shop I've used before. Very knowledgeable, but i think overly cautious. He spray carb cleaner around the intake and noticed slight changes. He things it's a small Crack in the intake manifold. But, then he said he'd recommend a new one if I could find it, but he wasn't sure that would fix things since the engine is tired. He started pricing replacement engines.

Any thoughts on things? Totally random and intermittent high idle. Sure, the engine is tired but normally runs great. The rest of the truck is pretty good overall. Thanks for your input!

 

What code are you getting??

 

For IAC and TPS, I'd recommend using only Mopar. Intake manifold is a composite material which looks like plastic but it's not. I usually don't see cracks in them. You can pull off the air hose, stick a rag down the throat and clean everything with carb cleaner, such as the butterfly and areas where it seats ... with a soft toothbrush. Check for cracks in hoses by squeezing along the lengths. Check the hose going to the brake booster and the one going to the back of the valve cover on passenger side. You can even fix these cracks by cleaning off the area with brake fluid and swiping some permatex black RTV on the crack. Not too much to push into hose.

Aside from bad oil maintenance and leaks, the biggest oil burner will be worn out valve stem seals. I replaced mine at over 300K mi (along with valve cover gaskets) and the truck burns no oil today.

https://dodgeforum.com/forum/2nd-gen...tem-seals.html

 

Thank you for all of that info! When I did the intake gaskets I replaced the pcv hose along the passenger side valve cover that goes into the rear of the intake manifold. I also had the throttle body off and cleaned it.

There is a small hose that connects to the throttle body and the end is questionable. I need to figure what size the rubber part is and replace that. I also should just replace the hose to the brake booster. Is snug but not tight at the throttle body.

I used napa parts for the IAC and TPS but it wouldn't hurt to put mopar parts on the eliminate that.

I drove the truck tonight for awhile and it runs great. It actually has a very smooth idle now. The high idle was there a few times, but it's almost like the idle hangs when coming to a stop. I can bump the throttle and it will come down to where it should be. 1000 down to 600rpm. It makes me think something is sticking. Thoughts?

I'll get the codes tomorrow. I know one is for a bank 2 o2 sensor. The other is for the high idle.

Yeah, I've read that valve seals cause most of the oil burning on these. When I idle for awhile and accelerate that's when I see all the blue smoke. I haven't gone into a truck engine beyond the valve covers or intake. Id love to replace those though.

 

The code I have is p0507.

 

That one is a result, not a cause..... but, it does indicate the PCM is aware there is a problem. Lots of stuff can cause high idle though, vacuum leak, leaking egr, or evap system, etc...... basically, unmetered air is making it to the engine. The intermittent nature of the problem though, would suggest it isn't really a mechanical problem..... some other system is having issues, and the PCM hasn't figgered out which one yet....

 

Yep, that sounds like the seals alright

 

Thank you for all of the information. I have a new Mopar IAC valve and TPS ordered. Should arrive next week.

Now, it's doing the high idle most of the time. Its very consistent and smooth, which is weird to me. I would think if it was a vacuum leak it would be fluctuate.

It did something really weird too. When it had the high idle sitting at a stop sign, 950rpm or so, I hit the throttle and there was no response. Took forever to speed up, then all of a sudden it went normal and really sped up.

 

Forgot to say you can cut a bit off the tip off the hose and reattach if too loose.

 

The parts arrived early! I put the new TPS and IAC on this evening. Fingers crossed. I drove it about 30 minutes and it seems good. We'll see how it does tomorrow.

This morning it was having issues shifting. Downshifting late and just acting weird. When i drove it tonight it shifting so smooth, couldn't feel it.

I'll definitely keep you all updated. The first shop I went to actually called me this afternoon to see if I figured it out. He said if it still acts up after the new parts to give him a call. He wants to figure it out, no charge he said.