Really strange idle problem

[jiggysnitz]

When my car is rolling it idles low (500rpm) and then as soon as I come to a complete stop it goes back up to what I have it set at (850rpm). Anyone know what could be causeing this?

 

[poonman]

clean throttle body and change idle positioning sensor

 

[DSM90AWD]

Unless it's stalling or idle is surging up-down.. I'd say you're ok.
If it does any of the above, then cleaning the TB/ISC (remove and clean inside with q-tip and solvant), boost leak checking/correcting and then verifying/setting Base Idle via the BISS would be in order.

FYI.. all bold words above will get you a ton of results if you wish to search for more info

 

[jiggysnitz]

Ok thanks alot guys. I just checked some of the sensors and the one on the back side of the throttle body that attatches with a little clip like a speaker wire (IAC? I think?) doesnt affect anything if I unplug it while the car is idleing

 

[tybo8127]

my 95 gsx tends to rev up to 2k and drop to 700ish and back up and down while idling. sometimes it just idles normal and then slowly drops down and stalls. also while cruising down the road doin about 60 when i take it out of gear sometimes it stalls. any ideas why? theres around 135k miles on it.. could it be something to do with the vacuum pressure.. possibly a leak?

 

[poonman]

Ok thanks alot guys. I just checked some of the sensors and the one on the back side of the throttle body that attatches with a little clip like a speaker wire (IAC? I think?) doesnt affect anything if I unplug it while the car is idleing

If you unplug the sensor and there is no difference then it sounds like the sensor doesnt work.

Try unpluging the Mass Air Flow Sensor and see if there is a difference. I know that if you have a dirty MAFS it will do just as you describe.

If you can get a new Idle Positioning Sensor try it out, alot of time if it doesnt make a difference you can return it with no problems and get your money back.

Also, is your check engine light on?

 

[poonman]

my 95 gsx tends to rev up to 2k and drop to 700ish and back up and down while idling. sometimes it just idles normal and then slowly drops down and stalls. also while cruising down the road doin about 60 when i take it out of gear sometimes it stalls. any ideas why? theres around 135k miles on it.. could it be something to do with the vacuum pressure.. possibly a leak?

Sounds like you have the same problem my firend. do what we recomended on his, to yours

 

[jiggysnitz]

Yeah, the check engine light comes on everynow and then. I thought maybe my O2 sensor was going but I'll check the MAFS. Oil change, New valve cover gasket, new plugs, new wires, clean throttle body, clean MAFS all goes in today hopfully that will make some difference!

 

[kahl23]

tybo, I had a problem with my idle going up and down from about 2k down to just above stalling and then back up. It turned out that the TPS had worked its way loose. Check all connections on the tb and see if that helps. Jiggy, the sensor that you unplugged is simply a sensor that tells when the throttle is closed. This is a redundancy (Mitsubishi engineering at its best) because the TPS will tell the ECU when the throttle is closed. I'd also check the ISC and TPS connections and see if that helps. If it doesn't, check out the VFAQ and look up the articles on cleaning a throttle body.

 

[poonman]

MAKE SURE my friend your are EXTREMLY careful cleaning a MAF, get yourself some SENSATIVE Electronic cleaner from the auto store, tell them what your cleaning and they should know just what to get

 

[kahl23]

Believe it or not, CRC now makes a cleaner specifically for MAFs.

http://www.amazon.com/CRC-Mass-Flow-Sensor-Cleaner/dp/B000EGH57G