Hi all. I have a 2003 with the 4.7. For probably 2 years or so, I've had this really inconsistent issue with my idle hunting. Only recently has it become more chronic and almost reproducible. I can say now with confidence that it only happens when the engine it cold, and only happens when transitioning from a gear to neutral or park. For example, if I move the truck with a cold engine a few feet to load it up, I'll get the loping idle as I move from reverse to neutral, then again as I move from drive to neutral and reverse to park. The other day I drove about 100 yards on a cold start across the property to load up some brush. As I moved from drive to neutral to reverse to back up to it, the engine stalled. First time that's ever happened.

I've really held out for it to get worse hoping it would set off a CEL that I could work from. It's at least bad enough now that I can make these observations. The loping can last anywhere from 1 second, to maybe about 30 seconds. In this time the engine RPM drops anywhere from around 650 RPM down to maybe 200 RPM. The tach doesn't really respond fast enough to keep up and makes watching it accurately harder.

I have Torque lite on my phone, and I've tried to watch various functions of the engine at this time. Nothing has really jumped out at me. The original TPS never really changed, and never read below 10.6% or above 75.x%. The new TPS sensor isn't really different, but it reads 12.7% as the lowest and 75.x% as the highest.

The plugs aren't very old, the TB isn't really dirty (cleaned like 5K miles ago), and I think I found all the vacuum leaks I had with the stupid charcoal canister. For giggles I also rest the PCM.

I threw the TPS at it since it was cheap and seemed like an easy culprit. My next suspect is the IAC valve, but I don't really just want to throw ~$80 at that. And the oddity of it only happening when changing gears makes me shy away from the TB anymore.

Any ideas? I'm not sure what to really examine in Torque to try and track this down.

Thanks.

 

Can anyone with Tourqe give my an idea what their 4.7 throttle body reads? I don't want to dismiss that I got a new bad TPS.

Short of any other ideas, I might just have to keep living with it until it get bad enough to make the culprit obvious.

 

Sorry, don't have Torque.


I had the bad idle situation for a while. I cleaned the IAC and it seemed to help for a minute, but not for long. Replaced the TPS with an OEM unit and the truck has idled glass smooth ever since.


You should get some carb cleaner and clean the IAC. Hopefully you got a Mopar TPS?

 

No, I bought an aftermarket sensor. I called the dealer this morning, but they were like "we need the VIN to find the part"... I might be willing to give it a shot if they have a return policy. I'd probably know almost straight away if it doesn't fix anything.

It's really hard to justify to much money for something that amounts to be a very minor annoyance.

 

https://www.amazon.com/Genuine-Chrys.../dp/B00FSDMYT4


It's about 50 bucks on Amazon. It was one of the best purchases for my truck, as it really smoothed out acceleration and idle back to car-like feel. Prior to that, the truck was real jumpy when accelerating slowly and sometimes would stall when coming to a stop.

 

Most common issue is the MAP sensor and / or TPS. Unless it sets a TPS/MAP Correlation DTC, then you may never see which one does it. You can also check for a vacuum leak that may only be present until the heat sets in and expands it closed.


When they come to me like this, I do both of them and avoid chasing my tail. It's cheaper for everyone (:

 

Every time I post, I swear it just vanishes...

I'll pick up a MAP sensor and give it a shot. I suspected the MAP too, and it's a pretty cheap sensor.

Thanks for the link to the genuine TPS part. I'm not certain that the new sensor is good, but I also don't think the old sensor was bad anymore.