I've posted about my idle speed running high, revving to 3,000 RPM, dropping to almost stalling, idling down the road at 40 MPH, etc.: https://www.crossfireforum.org/forum...high-idle.html

When it does this it, the idle speed will swing up and down like I'm a total tool at a red light. It's not just a high idle since it's also a bit jerky to drive pulling away from a stop and it will almost stall and then recover with a high rev again.

I've remapped the throttle position sensor and cleaned and replaced the MAF sensor. I found a post on a MB forum where someone had a similar problem that they cured by disconnecting the battery cable to reset the ECU. This worked for me as well but only temporarily - for a few weeks at a time. It acted up again yesterday so I disconnected the battery cable for an hour which seemed to "fix" it but it started again today.

This is really annoying and has my independent MB tech baffled as well. I'm hoping that someone has seen this and figured it out already.

 

What is your intake manifold vacuum reading.

Sounds like a leak on the intake???????????

let us know. WW

 

I haven't directly measured it but that was something I originally tried to track down using the gas from a propane torch which detected nothing. I don't know if my tech measured it a year ago.

I wouldn't think that a vacuum leak could recover for many months (or even a day) by doing an ECU reset via disconnecting the battery cable.

Thanks.

 

+1 you need to get some instrumentation on it, preferably with logging. IAT, coolant temp, MAP, RPM, throttle angle, that sort of thing.

 

I had this when a piece of rubber from a disintegrating cone filter jammed into the throttle body and held the throttle plate open a little. I think the car gets confused with the signals from the accelerator pedal signal and the TPS signal
So my guess is that the Throttle Position Sensor has failed. You should get the codes read to see if there is a fault set.
Even without the CEL on there can be a problem already diagnosed.

 

Thanks 180.

I was just looking at buying an Autel DiagLink. Do you think an AutoZone scanner would show those codes without the CEL being on?

A quick search found new throttle bodies for $1,400 but there are plenty of used ones available.

 

I would give them a try, I had no CEL when mine went haywire.

 

I have one for an NA that was running fine when we installed a 74 mm.
$50 + shipping.

 

Thanks. I'll keep that in mind.

 

Of course, when I drove to Advance Auto to read the codes it was running fine and there were no codes!

I'd like to buy your throttle body. Please DM me. Thanks.

 

PM has been sent.

 

I'm interested in buying your throttle body. PMs don't seem to be very effective.

I've seen some folks say to replace the o-ring and others say just clean it up. What do you recommend?

Thanks.

 

Mr Thanks :
Sorry about that - wife's been in the hospital.
PM me your address and I'll get it shipped right out.
See if it works OK for you, then you can paypal me $50 or so .....

NEVERMIND ! Checked my PM's and I see your address,
George

 

Thanks. I PMed you again. ;-)

 

Any chance you were able to figure out the issue. For the past month I have had something similar. Car acts weird once warm, especially after I shut it down and re-start it warm. The engine will do a few different things at idle/neutral depending on the scenario: Rev up and down between 1500-2200 rpms, stay idling at 1800rpms, or will get stuck around 3000+rpms if I tap the accelerator. I've tried to locate a vacuum leak, but I'm starting to thing its a bad sensor or an electronics issue. I've swapped MAF sensors, TBs, Accelerator assembly, installed new breather lines and T. Checked for vacuum leaks like crazy, reset the TB and reset the CPU. Works fine for the first trip then when I shut it down and restart after a shopping trip the issue resumes. Its drivable, just issues when I'm stopped or in neutral, in gear its ok. No CEL of codes. This is crazy.

 

Yes, you asked me this question on 11/11/20 and the following was my answer:

"Yes, it turns out it was the throttle body. I replaced it with a used one from a member on this forum and the problems went away."

 

LMAO! You get double stars for posting your solution twice, many (too many) never come back to tell us!


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