Mechanics

ERRATIC IDLE

2002 Dodge Dakota

Engine Mechanical problem
2002 Dodge Dakota V8 Four Wheel Drive Automatic 105000 miles

I have a 2002 dodge Dakota 4.7 V8, 4 Door, 4 wheel drive. It has 100,000 miles. It has never had any significant mechanical issues. About 2 weeks ago, it started idling very erratically. It would should up to close to 2000 RPMs at startup, then fluctuate between about 700 and 1300. At a red light, it would shoot up again and cause the truck to lurch forward. I took a video of what it is doing. Here is the link.
http://www.youtube.com/watch?v=FV2zGJs68SE
This is parked in my driveway after a 20 minute drive. Reading and speaking with a friend, I guessed it could possibly be the Idle air controller. My friend told me to :
"To clean the throttle body and idle control valve, they need to be removed and once on the bench, a good blast of throttle body cleaner in both will hopefully clean them out. Really saturate them to break up the carbon, I'd guess using a whole can of cleaner is not out of line. Compressed air to blow out any residue and carbon solids is helpful but not necessary if you were to put some elbow grease into them. Once they have been cleaned, let them sit so the throttle body cleaner can evaporate before reinstalling. This could take a while.
Well, I almost did that. I was slammed for time, and I have really only worked on carbureted vehicles. I called the Valvoline oil change place and asked if their fuel system cleaning cleaned the Idle air controller. They said it did. I figured paying $60 was worth having someone who knew what they were doing take care of it. It wasn't that thorough of a cleaning. He removed the square black plastic cover on the top of the engine. That led to what I believe is the throttle body. He dipped a stick with a cloth ball on the end into some cleaning solution and swabbed that around in the now exposed metal pipe. I'm calling it a pipe. It had 2 devices coming off the side. One the size of a salt shaker and one maybe half the size of a salt shaker. I believe one of these is the idle air controller. He then poured a fuel system cleaner in the tank and hooked up an 'IV bag with tubes' to the engine. I couldn't see exactly where, because I was pumping the gas when requested. He was flushing a fluid through somewhere and it was causing a ton of white smoke to come out the exhaust. Once they were done, I was thrilled. It seemed fixed. The problem which had occurred constantly was definitely gone. They asked me to go ahead and fill up on gas. I did. As I got down to about 1/4 tank, the problem started to come back. I have since had to fill up again, and the problem is definitely back. The video posted above was from yesterday. It is as bad as ever.
Any ideas? I am short on money right now, and would really like to avoid a trip to the mechanic if possible. I worked on all our car issues (and small engines) with my dad when I was a kid in the 80s and early 90s. I just haven't done a lot of work on more modern cars. What do you think? Should I try a more thorough cleaning of the idle air controller? Do you think that is what it is? Any ideas why the initial cleaning would appear to completely fix it, and then the problem came back within 2 weeks?
Thanks,
Matthew
Avatar
Mkitchin
July 10, 2010.



I watched the video. My guess is that you need a new throttle position sensor (TPS) or idle air control valve needs replaced. I see a red light on the dash. Is that the check engine light?

Would you start with the TPS or idle air control valve? Would you recommend replacing over trying to clean? The light is the parking break. I was a little surprised the check engine light has not come on at all.

Tiny
Mkitchin
Jul 10, 2010.
Without the check engine light, it becomes a guessing game. If there was improbement when you IAC, I would start there. And like you, I am surprised the check engine light hasn't come on.

I guess I will start with the IAC. It looks like it is $70 at auto zone. Would you recommend replacing over attempting to clean? I'm not familiar enough with these to know if it is worth trying to clean.

Tiny
Mkitchin
Jul 10, 2010.
You could try cleaning it. Stop at the local parts store and have them advise you on what to use to clean it.

All fixed. The IAC looked awful when I took it out. It wouldn't move at all and was stuck in a position significantly different than a new one was in when not in use. I went ahead and replaced it and the TPS. At first, it started reving constant around 2000 rpms. I had that not so good feeling, like I had done something to make it worse. Then I saw on the insert a note about how it will do that until you get the engine up normal temp and drive over 40 mph to reset something. Quick trip on I65, and all was well. Thanks for the help!

Tiny
Mkitchin
Jul 12, 2010.
I had a feeling that was the problem. I'm glad you got it fixed. And it was a good idea to replace the TPS too. Take care and let us know if you have questions in the future.

Joe
PS: Sorry it took a couple days to get back. I had a chance to go to Dover where they race nascar. It was great, but they wouldn't let me drive anything (LOL).