Hello everyone! I have a 2000 Saturn SL with the 5-speed manual transmission and 155K miles. This car has an occasional high idle issue (1500 to 1600 rpm's or so) after coming to a stop. It happens very infrequently, and so far I have always been able to correct it by switching off the engine and then starting it again and it goes back down to the normal 750 rpm. Otherwise the car idles fine and smoothly, with no rough idle at either the high rpm's or the normal idle rpm's. There is no check engine light (so far, anyway, LOL). I haven't yet checked for "hidden" codes with a code reader but I'll do that. There are no other driveability issues that I can detect and it accelerates and decelerates just fine and it gets good gas mileage (low to mid 30's mpg driving around town). Engine temperature is normal at 3/8 to 7/16 of the way on the coolant temp gauge when fully warmed up (this car has a Stant thermostat that appears to be functioning properly). ECTS was replaced with a brass unit a while back.

I think I read somewhere that this condition is likely the result of a bad throttle position sensor. Is that correct? If not, what are other possible causes here? Thanks!

 

Could be several things. I'd look at it with a scan tool when it acts up and see it the TPS is normal as well as other things.

 

Part of being an s car owner.
Needs a throttle body cleaning at most. I had my 95 SC2 do this for the first time in a while about 2 days ago.
I have always suspected that the throttle plate is not quite returning to home position.
My suspicion is bolstered by the fact that even a light on-car throttle body cleaning, including the back and edges of the throttle plate, iac and the throttle return spring takes care of the issue.

I just punch the gas pedal to 3K rom in neutral and it usually stops it from happening.
And as you described it is usually only at warmup, though there are times where it will sit at 1500 while warm. If I can't punch the gas to get it back on track, then a throttle body cleaning always does the trick.

 

Thanks Derf! Actually this issue usually occurs for me AFTER the car has completely warmed up (when it should be idling at 750 rpm). It has been a while since I cleaned the throttle body on this car, so I'll plan on doing that soon. I have used Seafoam in the past for that, and it seems to work well. However, I did hook up my OBD scanner (a ThinkOBD 100) to the car last night, and there is a pending code P0404 (Exhaust Gas Recirculation Circuit Range/Performance). There is no check engine light at the present time, so this seems to indicate an intermittent problem that hasn't occurred enough times to trigger the check engine light (yet, anyway). So should I remove the EGR valve and inspect it and possibly clean it? Or is the EGR valve bad and does it need to be replaced? This is new territory for me, so any suggestions based on any of your past experiences fixing similar issues would be greatly appreciated! BTW, my ThinkOBD 100 scanner is capable of streaming some data from the engine computer (although unfortunately it can't command certain devices/sensors to do certain things), so if there's anything I should be looking for in that data, please let me know that as well.

 

You should go ahead and remove the ERG valve and clean both it and the EGR tube. Derf can definitely walk you through that process. He's done it more than once!

 

Thanks Rubehayseed! I plan on removing and cleaning the EGR valve this weekend. You mentioned the EGR tube - where is that? It is not connected to the valve itself. There is a tube running off the air duct to the engine (part of the PCV system maybe?) - is that what you are referring to? For cleaning the EGR, I plan to use carb cleaner/Seafoam and/or brake cleaner and let it soak for a couple of hours or so and scrub out as much carbon as I reasonably can.

 

Carb cleaner will work fine. When you take the EGR off, you will see two openings. One is the incoming pipe with exhaust gases, the other is the output exhaust after having gone through the EGR. He's referring to what feeds the exhaust and what takes away the exhaust as pipes. The intake pipe is the one with all the carpet in it, well most of it.

The part that moves up and down to open and close the EGR is the pintle which is in the center of the valve. Be gentle with it and do not bend it or you will ruin the valve. I believe it has a Torx on the end of it for you to hold the pencil still while you clean the rest of it, and to work the pencil gently in and out until it returns to full range operation. You can also spin it

It should move freely up and down.

Once you are sure it's clean, clean it a second time.
Just trust me on this

 

OK, so yesterday I removed the EGR valve and cleaned it as best I could with carb cleaner. There was a LOT of carbon in it! However, I could not manually move the pintle. It seems stuck, and maybe that is the issue. So I ordered a new Delphi EGR valve from Rock Auto and will replace it with that. I also ordered a wire brush kit with various sizes of nylon, brass and steel brushes so I can more thoroughly clean the passages that connect to the EGR valve. Cost for all of that was a little over $100 including shipping. For now, I’ve reinstalled the old one and I still get the pending P0404 code again after clearing it. So I’m suspecting this valve is history.

 

You probably wasted your money. You can't move the pintle with just your fingers, Do you understand how it works?

 

Yeah, I hear you! I saw a video of the exact same EGR valve design where the guy was able to move it with his fingers after he worked quite hard cleaning it and applying voltage. Not sure I want to invest that amount of effort on this, so I went ahead and just ordered a new one. I probably could get this one working as y'all suggested, but this should ensure this problem goes away, or at least that the EGR is no longer an issue. I do plan on cleaning the EGR input and output ports as thoroughly as I can with nylon brushes (and plenty of carb cleaner) before installing the new one.