Help please. I have 2000 SL2 twin cam. Lately the idle has been sort of jumping...up, down, up, up, down, etc. I had planned to replace the TPS on Monday when the parts store is open because I figured that was likely the problem. But, today as I was driving I could feel the engine throttling up really high and sort of pulling me along. I pulled over and put the car in park and now the throttle wants to run wide open. I shut the engine off and back on several times but the problem persists. It just throttles all the way like it's stuck or something. Is it likely the TPS? Do I need to clean the IAC or throttle body? Vacuum leak? All of the above? Any help is much appreciated. Thanks.

 

It sounds like you might have a dirty throttle body and dirty IAC valve (Idle Air Control) valve. If the Idle Air Control valve pintle is dirty, this can cause your engine to idle roughly, too low, or too high. Or even in your case, to jump around. I would recommend inspecting the interior of the throttle body. All you have to do is remove the air intake hose, and open the throttle plate. If you see a bunch of dirt on, around, and behind the plate, your problem might be helped by thoroughly cleaning of the throttle body and the IAC valve.

A good way to do it is to remove the throttle body, remove the iac valve, and then use the correct carburetor cleaner or throttle body cleaner with some soft brushes to get it nice and clean to function correctly. If you're going to do this, make sure you have a replacement gasket for the Throttle Body to Air Intake. You also want to have a replacement O-ring handy for the IAC valve.

Here is an image of my throttle body before I cleaned it. It was causing problems with the idle and it was making the gas pedal stick badly. After removing it, removing the IAC valve, and cleaning it, the vehicle idled much more smoothly. The fuel trims also improved by about 5%.

Some mechanic friends said its one of the dirties they've ever seen. Have a look and see what yours looks like.



Here's a link to your particular throttle body assembly:

2000 Saturn Sl2 Throttle Body

Read everything carefully. Make sure to use a cleaner that doesn't contain methyl ethyl ketone.

If it doesn't look too dirty then the issue might be somewhere else, but I would start by inspecting the throttle body.

 

Wow! That has got to be the filthiest throttle body I've ever seen. And the car was still running with all of that crud in there? Saturns are amazing cars, aren't they?

 

Clean it on the vehicle first. If that doesn't work to solve your problem, then look into getting a new throttle body gasket and if you obtain one, then pull it off the car.

I recommend this instead of immediate removal because it's easier for the not terribly experienced to perform (not meant as a slam and if it does not apply to you, please ignore the comment) and doesn't really require any tools except those to remove their intake plastic tube.

Hold the throttle plate open all the way by rotating against the spring force when under the hood to ensure you get a good dousing on the back of the throttle plate. Use a throttle body cleaner not a carburetor cleaner. If it is truly scuzzy, you can use a soft toothbrush.

Be sure to spray down the spring for the throttle body and the plate shaft where it goes through the throttle body itself.

Again, try this without removing it from the vehicle first.

Indeed, give some attention to the IAC valve, But be gentle with it. Let the cleaner do the work. It's the opening on the bottom in front of the throttle plate. Things will run back out so I have a towel handy.

If you choose to spray throttle body cleaner into the throttle body while the vehicle is running, keep your towel away from the opening. It has some pretty good vacuum pull and you don't want your towel sucked in. Only takes once to learn your lesson.

Shine a flashlight down past the throttle plate and get a looksie i at the top portion of the intake manifold. You're not going to be able to get that clean while on the vehicle but most of the problematic build up will be in the throttle body for your concern.

Cleaning with The throttle body attached to the vehicle creates a bit of a difficulty in starting the vehicle if you spray too much throttle body cleaner down the intake without the engine running and burning it. Every so often you may wish to pause your cleaning and start the vehicle to clear out the built up dirty TB. rinse.

Some would argue that this method just rinses all the crap down to the injectors. I've never had a problem in 29 years doing it this way. Just saying.

When you do start the vehicle, it will act in a manner someone equivalent to a vehicle of old being flooded. Simply hold the gas pedal to the floor which clears the flood in this vehicle, and once it starts to fire, work the gas pedal up and down until you get it to idle. Sounds confusing first time, once you do it you'll understand.

If the idle air control valve does not get sufficiently clean, it may in fact stick open when it shouldn't, allowing extra air into the fuel mix, somewhat akin to a vacuum leak, or not close all the way when the car is at idle, also allowing too much air, both of these situations may well lead to extra air joining the fuel mix, often sporadically because the valve is fighting to open or close, it's not just sitting still. This may indeed cause of the RPMs to juggle / increase.

Please keep us informed and we will continue to assist you as necessary. Because that's what we do here.

 

Is that a woodworking clamp holding the throttle body open?
Never even remotely considered that. Guess I know what I'm using from now on.
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I take it that's a DOHC with nasty oil burning issues?
How many miles and how many quarts does that represent?
Ballpark......

 

Yes, I agree with derf about giving a try to clean it while its still on the vehicle. You can make a big improvement by cleaning the throttle body without actually removing it. Maybe you can do that first and then see if you get a positive outcome.

 

Yea! its a IRWIN Quick-Grip carpentry clamp.
She is a SOHC, 175k miles, and it does consume about 1/2 to 3/4 a quart of oil every 500 miles. I'm going to start using high mileage oil on the next oil change, and I am planning to use some high mileage SeaFoam in the crank case for about 100 miles before I do the oil change, so see if that helps the oil consumption. Any tips on how to reduce oil consumption? Or preventing it from getting worse?

I bought it at 120k miles, and I'd never cleaned the throttle body before. So its at least 50k miles of buildup.

 

Search saturn mmo soak.

Depends on how bad the oil control rings are varnished as to how much you can loosen them up. Helps for some, doesn't for others.

Also search on Saturn Seafoam and give that a whirl as well.