Extremely high idle, impossible fix.
 

Hey all. I need some help badly. I have owned nothing but Honda's all my life, and due to my circumstances, I no longer own my new Honda, and was able to pick up a running 1998 SL2 for $500. Now the story.

I was in need of a car (so I didn't have to bicycle in the winter here in Ohio). New car completely out of budget, I met someone that sold me a running 98 SL2 for $500. The thing idled at 2200 rpm, but hey, it ran and shifted great (5-speed) all working lights, AC worked, etc for $500, so I grabbed it and took off.

My thought was hey, I'll tinker with it a bit and get that idle back to normal. Seven days into ****ing with this thing and 2 new sensors, nothing. Here's the details.

I initially took it to Autozone to have them scan it. It threw a bad O2 sensor (like every single car that's not brand new does) and it threw the IAC motor. Perfect, $40 and ten minutes, car is fixed.....No. I put the brand new IAC in, and now car idles at 4,000 rpms. I did the whole reset computer thing (disconnect negative on battery for 5 minutes, start, engine, let warm up, drive steady 40mph in 4th gear, shut off for 1 minute, restart, and idle "will" reset). Another negative. The car started overheating and boiling the over flow antifreeze. After reading some less informative forums, people that have this problem run with the AC compressor ON to combat the over heating issue. While this is working, I'm still idling at 2500-3000 rpms.

More hours spent on forums, I saw that there was a vacuum test to be done. Disconnect the massive air intake tube from the throttle body (which was shiny clean the first time I took the TB off to put the new IAC in), place your thumb over the IAC bypass valve, and engine should die. Rpms went from 3500 down to about 700. OK, we have a vacuum leak somewhere. Forums had advised me to spray WD40 around the intake gasket (#1 cylinder reputably), PVC valve and hose, and if there is a vacuum leak, idle would surge. Nothing....and I hosed that bitch down with the WD-40. My engine purred perfectly at 3200, not reacting a single bit to the WD40 drowning the engine bay. My gearhead buddy was here for that test and said "Dude, that's your TPS man, just replace it and you will be fine." So, another $50 part, installed, the whole "reset your ****ing computer thing" and still, I have high idle. Mind you though, now I'm at about 2700 rpms instead of 3000. It seams every little thing I replace brings the rpms slightly down. So I figure another $400 and a few more parts and I may be in the 1000 rpm idle I would like (this is sarcasm....it's been a frustrating week).

Here's a side note. When I do cruise along, it still will want to push up to 2500-3000 rpms. Depending on which gear I'm in, it's kinda like having ghetto cruise control (har har). Every five minutes or so, with my foot OFF of the accelerator pedal, the engine will sputter a bit and seem as if now it wants to coast down to idle speed, then it will remember it's on cocaine, and swiftly get back up to 3000 rpm and regain its "cruise control".

I'm at a loss here guys. What in Sam **** is causing this high idle?! I know nothing of the SL2 line, and I really want to get this fixed. I realize I have a running vehicle for $500 and should be happy with that, but if I can get the idle fixed, I could probably drive this thing for another five years reliably (it only has 196,000 miles, zero rust, absolutely no ticking in the engine at all, manual trans shifts better than my new Honda did, etc).

I have spent all week on forums, calling dealerships, talking to "gearhead" friends, and I get different answers from everyone, and its draining my bank account. Is there a fix to this, or will I need to race everyone I am next to at a stop light because they think I'm picking a fight with them "revving my engine"....

Please help.

Best wishes,
Jeremy.

Try reading all the posts on the subject.

Go to the new member area and give yourself a proper introduction. Then take a minute and open the USER CP top left of the page and add your first name, location, and car info to your "signature"

It MIGHT be your ECTS. Do NOT purchase a new one anywhere except from a Saturn friendly GM dealership. The aftermarket ones are not calibrated correctly and generally are a waste of money. Take a close look at the connector to it too. You may want to go ahead and replace it too. Both parts together run around fifty bucks. The new one needs to be brass tipped and not resin tipped. If they try to give you the resin one, tell them no, you need the brass one.

New Findings.
 

I tore into it again after work today. The ECTS looks brand new and the connector is nice and clean. I installed the new TPS last night but did no vacuum checks. Today, I pulled off all vacuum hoses to make sure they are free and clear of cracks. They all passed with flying colors. I removed the air intake tube, covered the TB inlet with my palm, and the engine instantly died. That rules out any vacuum leaks, correct? The only two things I have not replaced is the ECTS and the EGS. Any clues guys? I feel like the vacuum check may help point in the right direction.

Also, the Low Coolant warning light is lit on the dash. There is really no coolant in the over flow under the hood. I am pretty mechanically inclined and don't see how low coolant would cause high idle, but again I do not know the SL2 line well at all. Please HELP!!!

I THINK you can rule out vacuum leaks due to what you've done. Where are you purchasing your parts? If at Autozone, that may be the problem. As a former employee and parts manager for them, I saw a lot of returns on electrical parts. They're crap. Find yourself a nice Saturn friendly GM dealership and get your parts from them. Yeah, you'll pay more, but at least you know you're not getting aftermarket parts that are not up to spec. I'm relatively new to Saturns too, so am not a lot of help. I don't see how low coolant would do that, but you never know with some cars. Top it off and see what happens. I think your problem is related to the throttle body somehow. I'd pull the damn thing off it were mine, take it apart and give it a thorough cleaning and put it back together. Check all of your electrical connections and make sure they're clean and tight. Just a little corrosion on one can drive you bat**** crazy!

If you have the original IAC, put it back in, the ones AutoZone sells will always idle high. Next, check the throttle stop screw. This is not an idle adjustment but some people have been known to turn them in to keep the engine alive when it won't idle at a reasonable RPM. Back the screw out until there is a gap, then screw it in until it just touches the throttle stop, than about a quarter turn more should do it. If it still idles high, back it out just a little.

If you can't get the idle down with this, then you have an air leak somewhere or the wire from the PCM to the IAC is broken.

I failed to mention that I have tried adjusting the idle screw in every which way. As a last ditch effort today, I checked the fuse box to see if I had any blown fuses, and of course, none. Then I pulled the electrical connector off the MAP while engine was on, and the car died (so my assumption is a bad MAP is ruled out now). At this point, I figure I'll just return the TPS and IAC I just bought (yes I saved the old ones) and use the return money to have the $99 engine diag done by a professional mechanic (not auto zone).

I have a feeling that the issue is going to be some incredibly minuet thing that has been smacking me in the face this entire time, with a correction cost of maybe $10. But whatever it is, I can't find it. Rather than keep sinking $50 a day in a new damn sensor, I conclude that it's time to give in and let the pro's handle it (or the guy that has the pro diag computer if you will). If you guys have any more thoughts, please post, otherwise, I'll let you now what the super computer down at Firestone tells me. Thanks again guys.

Have you checked your EGR valve, man? I'm not sure when it comes into play, but if it's carboned up real bad and not allowing the pintle to operate properly, maybe that's it. Take it off and clean it and the intake passage and see what happens. Nothing ventured, nothing gained, right?

Find the answer to the idle problem. Let us know what you found.

steve stewart
 

just trying to clear up the high idle problem for people . Most high idle problems with no trouble codes . high idle 2000 to 3000 will need a new throttle body, this means no parts store parts. GM only then vehicle will have to be reprogrammed by dealer ship or a local shop.

Steve, you do realize that thread is almost 4 years old and the OP was banned, right?

Thank you for the tip, Steve.

May be true for other brands in the GM line, but in 13 years of moderating this forum, i don't believe we've EVER had a single owner have to replace the throttle body on an S series to achieve a normal idle 850 ish on a M/T).

1st design ECTS failure and associated connector corrosion accounts for about 70% of everything that hoses the operation of the S series engine.
Front O2, dirty EGR, vacuum leaks (especially at #1 on 2nd and 3rd gen SOHCs -- the gasket gets partially sucked into the port and therefore unmetered air gets in and messes up the A/F ratio......) CKP (no signal = no spark + no fuel inj pulse = not gonna run.

My guess (since I never took one on this thread) is that

1)the ECTS was not a GM sourced ECTS. The BS ECTS in there was defective or failed. As they usually failed open, the V across it (0) is translated at the PCM as about -40. It never changes. Engine heats up. If cooling system is tight, temp usually stabilizes and you are fine until you get stuck in traffic and the coolant temp rises b c there is no air flow across the engine.

The aux cooling fan enable is triggered by the ECTS, which is always interpreted as-40 in this case. So the cooling fan never turns on and the engine overheats.

I don't know if his expansion reservoir was almost empty from overheating and him not refilling it or if the cooling system had a leak. I suspect both, actually.

Running with a SUPER RICH mixture meant for -40 degrees will jack up your idle into the 2K range (not uncommon).

I bet a simple throttle body cleaning would have been the first one the car ever had and would have allowed the plate to move freely to its intended destination, and the idle air passage would have been cleaned out to allow the proper amount of air to bypass at idle. As it was, that passage was probably restricted, not allowing enough air into the mix regardless of IAC operation. This, in turn, would force the engine to get the needed air from SOMEWHERE to satisfy the A/F ratio commanded in the fuel map for idle. That somewhere would be a vacuum leak, most likely at the intake manifold. If it was a metered air intake, the idle would be expected to go down; since it is unmetered the rpms go up since the air isn't accounted for in the A/F ratio to determine fuel requirements.

IIRC, the PCM will get the rpms as close to normal idle as it can by futzing w the air/fuel ratio, but will stop futzing when it determines no further improvement can be made.

Also the fact that the vehicle seemed to run smoothly otherwise removes a lot of things from the equation.

Throttle position sensor? Not really consistent with the ghetto cruise control he mentioned since it was not a constant FORCED rpm but more of a mutating one that slowly rose. Could have been checked with a DVM.

So in summary:
1) Dirty Throttle body and restricted idle air passage
2) Prob IAC from being gummed up
3) Non-GM sourced ECTS and almost certainly failed ECTS
4) Vac leak
5) Possible cooling system leak

I understand why the guy sold it for $500. It is a confusing mix of issues contributing to the observed behavior if you don't know Saturn S series engines.

Another useless forensic analysis completed that hopefully partially convinces Steve that the S series engines had some common issues of their own, but throttle body replacement was never necessary (in that I've not seen it recommended on this site, not that it is never the issue)

I'm sure there are cases where it is warranted, but, like S car PCMs, failures are few and far between.