out of control RPM at idle
 

my gf has a 99 sl1

when she brakes and pushes in the clutch the RPMs go up to 4K and when she's at a full stop it revs high and sometime stays up there and sometimes decreases. no rhyme or reason

ideas?

200K on it.

also at inspection the code for EGR was on but i just cleaned the EGR and ran the car and it passed legally. could this be the EGR getting dirty again?

Hmmm,

1) I would start with a thorough throttle body cleaning and see if that helps. Be sure to get the back of the throttle plate and the small passage at the front edge(Idle Air Control (IAC) valve) nice and clean using throttle body cleaner (not carb cleaner).

2) SES light on? Any codes? Please post as Pxxxx, not the text description

3) You may have a crack in a vacuum line causing a vacuum leak. It may be that the vac line is flexing or getting jostled around while you drive. in the right position, it leaks, in he wrong position it doesn't , and everywhere in between. One of the usual suspects is the vac line from the PCV to the throttle body.

4) 4K is the RPM where the rev limiter kicks in to prevent engine damage when the vehicle speed sensor output tells the PCM that the car is moving 3 mph (approx) or less.

Is it pinned at exactly 4K RPM, reproducibly, and only below 3mph?

If the Vehicle speed sensor (VSS) was an issue I'm pretty sure it would throw a code

5) Try the following:

When the you brake to a stop in an area where there are no other cars AND the RPMs are sticking high at a complete stop, turn off the engine. Count slowly to 5 and restart the engine.

If the engine idles normally (850 ish), the throttle position sensor is likely the culprit.
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Most EGR issues are a result of carbon buildup. Either the center pintle, whose position is constantly monitored electronically at the top of the unit, gets hung up, can't close all the way, or can't open all the way. The EGR codes are usually for insufficient flow, pintle not where it was commanded to be, etc. Most EGR issues show up on accel and decel.

When she puts the clutch in for every shift, what do the rpms do while the clutch pedal is down?

Personally, I don't believe this to be an EGR decel related issue, as the RPMs often gyrate up and down all over the place.

You will need to keep up with the EGR cleanings, as it will get carboned up more quickly as oil consumption increases. Sometimes you can get a second cleaning ot of them, sometimes not.....