Lumpy idle! Help!

[jonlisle20]

My car has 17,000 miles on it now. A couple months after I got in the accident, at about 10,000 miles, my car started to have a really lumpy idle. As RPMs come down the tach settles at about 700. After a second or two, it starts to dance. It pops up 300 rpms, falls just under 700, and continues on like this until it settles at about 400 rpm. Just as you think it's done it starts back up again. This all happens randomly. The only predictable aspect of it, is that it will definitely happen at some point during idle. DEFINITELY.
Because I have an intake and exhaust, this lumpy idle is extremely noticable. (my intake pops, my exhaust revs, and my sanity wears thin) What could be the problem?
I have already taken it to two dealerships and they assure me that nothing is wrong. They hooked up their computers and said that nothing was wrong. After I bought a new MAS.....assholes.
The head technitian told me it was the O2 sensors constantly changing the air/fuel ratio. bulls***! The car was bone stock when this started to happen and it didn't do it before. No other MP3 has done this. (To my knowledge) He came up with a bunch of other excuses but they were easily proved wrong.
The car preforms great when driving so I just let it go. I'm really stumped guys.
Could this be my fuel injectors? (I use 94 octane)
Maybe my spark plugs?
My O2 sensors?
A kink in one of my ECU wires?

ANY info or suggestions you could offer would be highly appreciated. Thanks, Jon.

 

[1sty]

I have been having a similar problem and my Haynes manuel for my old MX-6 proved useful. The manual covers the 2.0L that was in the Probes but is close enough to ours to give some good ideas.

Under Troubleshooting
Engine lopes while idling or idles erraticly:
- Vacuum leak
- Defective EGR valve
- Fuel pump not delivering sufficient fuel to the injectors
- leaking head gasket
- Timing belt and or pulley worn
- Camshaft lobes warn

my problem stems from the addition of both my 180 amp alternator and turbo. I basicly just turned up the idle screw from 700 to 850 and most of my major problems subsided.

 

[promp3]

hmmmm... interesting, if the shop did a full dignostic cheack and it showd nothing wrong!? I find that hard to belive I would try reseting the ecu just to elimate that (disconect the negitive terminal on batt. step on brake...wait...conect it...wait...lights blink...done) I doubt that is your problem but I'd try and elimate all posssabiltys, cheack all visual things, Like make sure the MAFS is not in backwards,hoses and wires are all in good condition just rule out the simple things first.

 

[cyomega]

Replace your spark plug wires. 99.9% that's the culprit. Plus, they're pretty cheap.

 

[promp3]

thats a good point...I'd get some sparkco wires

 

[KYREDP5]

Two words IAC Valve. Probes & MX6's are famous for getting stuck. I would imagine ours aren't mush diffrent.

 

[1sty]

Two words IAC Valve. Probes & MX6's are famous for getting stuck. I would imagine ours aren't mush diffrent.

Can you describe how to diagnose this problem and determin that is infact the IAC?

 

[KYREDP5]

The IAC (idle air control) valve is what delivers air to the to the engine while the throttle is closed. When mine was acting up it would drive 100% normal, untill I stopped. It sounds like yours may be just partially stuck. It usually doesn't need to be repalced. Usually just a cleaning will do. It's the little cannister looking thing over the IM. Your a member of PT right? If you'll ask over there one of the members has a page showing how to clean it. If that's not the problem then all you lose is $5 for the cleaner and about an hour of your time. Not guaranteeing that it's the problem, but it's worth a try.

 

[J Goodz]

I've been having the exact same problem w/ my car's idleing. I only have an intake but it's been happening way before i got that. I'm gonna try new spark plugs and if not try those sparkco wires. Please keep me posted on your progress.

 

[jonlisle20]

Thaks for all your suggestions guys. I'm going to get started on them asap. I'll let you know.

 

[alec172]

I have some of this problem when i start the car. I only have a CAI from Injen but when I start the car, it fluctuates until i step on the gas pedal. It sounds like the IAC valve. Any picture of it?

 

[alec172]

I have some of this problem when i start the car. I only have a CAI from Injen but when I start the car, the idle fluctuates until i step on the gas pedal. It sounds like the IAC valve. Any picture of it?

 

[1FastMP3]

I think your ignition wires are breaking down on you. I had a somewhat similar problem with my Harley. I took it in and when I got it back they said it was just the wires. Good Luck Bro

 

[jonlisle20]

I just installed the Sparkco Ignition wires and Bosch Platinum +4 spark plugs............and NOTHING has changed! Lumpy as ever!
Time to try out the Idle Air Control Valve suggestion. I'll keep you guys posted.

 

[J Goodz]

s*** i was hoping the wires would fix it. keep me posted.

 

[FuNwaGoN]

Hey guys dealing with much the same issue. I am on my 3rd trip to the dealer and they are now telling me that it was my IAC valve the entire time. First they said it was my ecu and then they said it was the base idle and now the IAC valve. Check my thread under Strange Idle??? Possible clicking sound related/ Sorry to say this but I am glad I am not the only one that has had this problem. Not saying I am happy you guys have it but this proves to the dealer that I am not freaking crazy or alone with this problem.

 

[jonlisle20]

Sorry to say it but I'm glad someone else has it as well. PLEASE let us know what happens ASAP! I've been dealing with this for months. Thanks in advance, Jon. Oh yeah, no, you're not crazy............yet!

 

[J Goodz]

ditto

 

[FuNwaGoN]

Well according to my dumbass dealer, they say it was the IAC valve. They said that it was faulty from the factory and that is why I was having all of my problems. Down side is that since I found out that my car has been messed up since I bought it, I am really not sure anymore as to how it is supposed to run or drive. I have never driven another P5 or MP3. I bought the first one I drove. I am just really confused right now. Here I have spent all of this money on this new car and have had such a bad experience at the dealership and the uncertainties they discovered about my car that I have been thinking about selling it. Well that is if it doesn't happen again and make up my mind for me by qualifying for the lemon law program. The thing that pisses me off, irkes me, and just makes me uneasy is that every time I left the dealership they said"Your car is good to go and is driving just like it should be." And every time a day or two later the car has messed up again. Also am really worried that because I drove my car for 4000 miles messed up I wonder if that caused or will cause more problems?????

Wish I could give you guys an answer as to if this fixed it or not but the truth is that I just don't know. It drives and runs completely different now than it ever did before. But I can say that they gave me a bill (warranty paid for it) for $300 stating they changed the IAC Valve and misc. diagnosis and labor charges. IAC Valve alone was over $200.

 

[KYREDP5]

Hehehehehe....Told ya it was the IAC. Glad you found out what was wrong