Idle issues
 

Alright, so, I am having weird idle issues regarding my 02 SL1. When I bought this car back in May, it had a bad intake manifold gasket and the wrong gap on the number 1 plug. Had a dead miss at idle when I purchased it. I fixed those issues and it has been running fine. Now, at least once a day, the idle speed will go from 750 rpm to 1500rpm and stay there until you shut the car off. If you start it right back up, it idles at 750 again. Also, sometimes it will idle too low. When this happens it will droop down to 500rpm, almost die, and then come back up to 750.

This happens intermittently. When it started I replaced the ECTS with a AC Delco unit, and replaced the plug by soldering it into the harness. No service engine soon light either.

My question is, will a bad Idle Air Control Valve not throw a code?

Any help is appreciated.

as I've learned over the years and continue to learn, DTCs are only set when criteria are not met. The key is----what are those criteria????

Unless there is no voltage / open circuit or the reading is completely out of whack with something else it should be tracking with, alot of things you might expect to throw codes DON'T simply because they don't meet the designed criteria.
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Take the ECTS: 1992 old resin tipped one. Reading the equiv of -40F. That's WHACK......unless you live where the temp is -40F. Result: No code

Pull the connector off? Code--CTS low voltage.....CODE.
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I think that's why unless the IAC's and TPS's on the saturns are reading voltages outside the design ranges OR the data is not tracking with something else within reason as it should, they don't throw codes.

Sounds like a TPS issue to me. Notorious for whacked behavior like that which can be cleared as if it never happened by powercycling the car

TPS as in throttle position sensor?

Indeed

Screws are T25's I think

(just stole that info from Richpin never disappoints.....said in the replies to the comments he actually had the problem himself. Also noted, however that if it is very very intermittent it may just be loose / poor connection.

Put some hockey tape on those knuckles

Lol, I wish I had skin on my knuckles to protect. I'll pull the connector and look at it. I will report what I find.

I was unaware that a manual car with a cable throttle would have a tps. Learn something everyday.

Thank you good sir.

Rob

Edit: That makes sense now. Something has to tell the ecm how far open the throttle body butterfly valve is.

I just had some fun with my TPS on my car. Check my threads to read up on it. Also be wary of where you get your parts. Stuff made in Taiwan isn't always the best things.

Agreed, as Rube would caution if he was logged on right now.
Thanks for the reminder, Dave

Avoid AutoBlows, Advance, and the like. NAPA parts are often a step up.

Rockauto,com is pretty much the cheapest reliable place to buy quality parts.
They usually offer everything from "economy" (= crap) to very high quality parts depending on what it is. I tend to stay w AC/Delco when possible.

Just stay away from the really cheap stuff and you will be fine.
The mid grade stuff is made in a nicer part of China.

Got one in from Rock Auto yesterday afternoon. Took about 10 min to install. It wasn't as close to the firewall as I thought. Maybe the single cam engines have a little more room back there.

Anyway, seems to have solved the issue. I have only put 20 miles, or so, on it since the change, but no weird high idle now. I will update the thread if anything changes. Thanks Derf, for the point in the right direction.

No problem, Rob.
My pleasure to help out another satty dude keep their ride running smoothly.

When you remove the TPS, you can see the coil of wire and the wiper that make up the rheostat. Its usually a little corrosion or dirt on the wire that causes the issue. It can be cleaned with some MAF cleaner, gumout or just some rubbing alcohol. I just dropped mine into a small cup of rubbing alcohol for a hour or so, worked the wiper a few times and reinstalled, no more issues.

BTW, this was on my 97 Nissan Pick Up, my Saturn never had an issue with the TPS.