Engine is reving itself at times and holding high idle??

[bmwtinut]

Well I have taken a look at the forums to try and find a solution to what could be causing my issue and don't see any resolution to anyone that has had a similar issue.
What is happening is that at times my idle is a little high, 1100-1000 and then will eventually settle down. No specific pattern to when this will happen. Havent worried about it too much. Well now a couple of weeks ago I come to a stop light and have the clutch pressed and the idle starts to slowly work its way up to 3000 to 3200 rpm. I pressed on the gas a little and nothing, press harder to bring the rpm above 3000 and then it settled down to about 1000. A little bit later I noticed this when I went to down shift as I was slowing down, the revs should of dropped due the to change in speed but I noticed that as I pushed the clutch in the rpms started to rise. When the clutch was engaged it smoothed everything out and idle was back to normal. I have noticed the idle spiking on its own several other times since then. It does not climb steadily but in small surges. Very strange. I am thinking ICV or the throttle pos sensor.

I also have had very rough idle when the car has sat for a while and not run especially when it is very cold out. Maybe a temp sensor?

Is there any way to check the ICV or Thottle pos sensor, resistance measurements ect?

The car is a 95 Clubsport with 165k on it. It has been my daily driver for the past 10 years. I have already replaced the ICV back around 90-100k and cleaned it last summer. I do still have the old ICV and a complete spare engine(70k) with the sensors to check values against.

I checked the resistance value of the ICV at rest on the spare engine and my engine and got the same value. The old unit was a lower value. Sorry I don't remember what the values were.

Just wondering if anyone has suggestions.

Thanks
Todd

[bmwtinut]

Anyone?????

[Xenocide]

check intake boot for tears/holes

[Philly]

My car even with my swap has done this on a couple occasions since complete.
Exact same thing, but mine always seemed to happen after a really hard rain. Now long story short I have my postcat O2 sensors and my FPR wires ghetto'd up and I found them hanging off a few times. Probably from hydroplaning and ripping them out. It happened a few times last summer, I can't remember what I did to make it stop, I didn't replace any sensors - so I think that may be wiring related?
Anyways, last time it happened my car wouldn't start, after moving it down the driveway it finally started and revv'd itself up 3500, actually fell off and stalled once...so I did a better ghettojob on the wires and the car worked fine again. I think it had more to do with the FPR wire than anything else.
Im sure a number of things could cause it but I replaced my boot as well and i still have funky idle issues, can feel the car surging sort of and hanging around 1k before settling, sometimes I can help it go down to normal idle range by sucking voltage by holding the window button up or turning on the HVAC quickly.
Will yours do that?

Id like to get to the bottom of this to.

[dave45056]

bmwtinut,
Have you checked any codes? That would be the first thing I'd check.
Let us know what you find.

[bmwtinut]

Quick update, barely got out of the driveway this morning.

Car was revving like mad and almost stalled. Pulled this flash code, check engine light was on. 1216 - Throttle Potentiometer

looks like a new throttle pos sensor is needed.

[Philly]

did you replace this yet? if so, problem solved?
my car just started acting abit funny again...

[bmwtinut]

I haven't replaced the sensor yet. I did finally get to take some measurements on my sensor and on the one on the spare engine that I have. I used the procedure and values in the bentley manual.

5v ref signal on wire harness passed.
4k across terminals 1 & 3, passed.
Resistance across 2 & 3. 4.59k to 1.78 seems high.
Strange thing that I noticed is that when moving from 4k down when I get to about 2.7k the resistance goes to infinity, or OL as my meter shows. Then back to about 2.6k until I get down to 1.78. Now if I bring the sensor back up when I reach 3.1 to 3.2k it goes to infinity again. Then smoothly up tp 4.59k. The upper and lower limits were with the sensor in the car. Out of the car the performance is the same with the same breaks but the upper and lower limits are farther out.

I tested both units that I have out of the car 1st and both exhibited the similar break or gap. Ran out of time to really test both in the car. Took some videos of the car though.


Can anyone get some values off of a sensor and see how it behaves? That would help.