Idle speed is 2100 rpm

I have a '94 SL1, manual, 100k miles.

For the past few weeks a high pitched whine could be heard coming from the engine compartment after about 3 mins of idling after start-up in warm weather and would continue while driving. The pitch or frequency of the whine didn't change with increased rpms up until 3000 rpm, after which the noise would go away (and return when the rpms dropped below 3000 rpm).

Then 2 days ago, the noise disappeared, but the idle speed has increased dramatically. Now on initial start up the idle speed is 2500 rpm and after about 10 seconds the speed drops to 2100 rpm and stays there any time the car idles during a trip.

Also, the service engine light comes on intermittantly over this entire period.

I checked the codes and got 35 and 49.

Can anyone advise me on what needs attention and where I might find the item(s) in the engine compartment?

Thanks in advance.

35. IAC valve, rpm out of range
49. Idle rpm out of limit high (vacuum leak)

49 says you have a high idle, 35 says the idle air control isn't helping.

try the pinpoint the source of the vaccum leak(start with the vacuum lines). a vaccum leak can make a hiss noise, any chance this is the whine you hear? also try cleaning the throttle body/IAC with carb and choke cleaner. carb and choke cleaner can also be used to confirm the area of a vacuum leak. spraying the cleaner on the suppected leak area will cause the engine rpm to drop if in fact there is a leak.

There is no hissing / whining sound now. That all stopped at around the same time as when the idle went from normal to 2100 rpm (co-incidence or could the IAC valve have been making the noise??).

I'll check for vacuum leaks as you suggest. (Not sure if I will get to it this weekend).

Once I started looking for vacuum leaks, I realized that I'm not too sure what to look at or for. There was no obvious leaks on the few lines that I did look at. However, if I knew the answers to the following questions I'd be in a better position to evaluate the situation: What lines make up the "vacuum lines"? Would a leak be easily visible or audible or would it be a hairline type crack?

Anyway, I felt that the IAC valve was at the root of the problem, so I took a flyer and replaced it.....no change...idle still 2100 rpm. The IAC valve did come with some idle rpm reset instructions (eg drive at 40 mph or idle for 1 min and the PCM establishes an accurate reference with respect to the pintle position). None of them seemed to work. But I was wondering if it would be worth resetting the PCM and, if so, how would I do that?

I have a similar problem. My 1997 SC1 started to idle around 2000 RPM each time I came to a stop or started the car. After a few seconds, it would settle down.

On a whim, I changed the IAC valve. Now it seems to just floor itself to around 3000 RPM all the time (it feels like someone's pressing on the gas). I checked the voltage on the IAC connector as shown in the repair manual, and it stays at 10.9VDC, but does not fluctuate as the manual says it should. I tried driving around my neighborhood hoping that the PCM would adjust, but it didn't.

Do I need to take it out on the highway to get the PCM to adjust? I bought the IAC valve at Autozone ... could it be bad? Any suggestions?

Thanks,

Chris

Ya, you can hear a vacuum leak as Seirrap mentioned. There should be a vacuum schematic under the hood that will give you a better idea of whats there. Start by checking the rubber hoses. They can be either brittle and cracked or soft and gummy. Neither is good and they should be replaced. Also check around the intake manifold with the carb and choke cleaner. Try around the passenger side of the intake especially.

Creelove, The IAC valve has to be adjusted to a zero position when installed so the PCM knows where it is. See Idle Air Control Valve (http://www1.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/19/a0/0e/0900823d8019a00e.jsp) . Did you clean the port the IAC fits into?
Also have you updated the ECTS to the brass tip design (saturn oem part). The original composite/plastic tipped one will fail and cause a lot of problems. Cheap fix/insurance. Got mine at saturnparts.com for under $20.00 including $8.50 shipping and handling.Install is not much harder than changing a spark plug.

You can reset the PCM by either disconnecting the battery or pulling the PCM fuse. Look it's location up in your owners manual.

Problem fixed! I took the new IAC valve out and extended the plunger in and out of the valve by twisting it like a screw. I left it about half way extended and re-installed it. I also disconnected the battery to reset the PCM.

Once it was reinstalled, the idle immediately settled down and after taking a quick drive and letting it run, the idle is back to around 650 RPM and doesn't rev when I go into neutral. I guess the plunger was stuck in the valve and needed to be loosened a bit.

Thanks so much!

I love a happy ending. :smile: Click on the link I put in my last post. It is for autozones online repair manual. Specifically the IAC. Lots of good info on that site. :thumbsup:

I followed Autozone's online repair for the IAC valve - however, I didn't have the same outcome as Creelove.

I measured the voltage at the 4-pin connector to the IAC valve. Autozone says that I should see 0 - 10.5 volts. I saw a constant 11.5 volts at A/B and C/D. (Note: the old IAC valve looked like its coils were fried).

I reset the PCM - no change - still idles at 2100rpm.

Then I removed the IAC valve again and screwed out the pintle closer to its max extension. When I started the engine the idle was initially 1000rpm, but it then raised gradually over a minute to 2100rpm again. When I inspected the IAC valve again the pintle was not as extended as when I initially put it in.

What does all this tell me?
What input / condition is telling the PCM to apply a constant 11.5 volts to the IAC valve?

i don't like the way Autozone.com has that writen up(which is just a copy of the Chilion's manual) there is a better way, but a bit harder.

after reseting the PCM, it may take a few miles for the PCM to relearn what it needs to set the idle.

but besides that - see if the codes come back, and if the idle does not inprove in the next day, repost and we will double check for vaccum leaks.

Remaining code = 49.

Idle speed still at 2100rpm, even after resetting the pcm and driving for a bit.

first, buy a can of carb and choke cleaner, clean the throttle body and IAC. start the engine. give it a minute to get running, then spray lightly around the exterior of the vacuum lines, PCV hose, throttle body to intake manifold gasket and intake manifold to head gasket, and anywhere else a vacuum leak is possible. if the sprayed area is leaking the RPM will drop briefly. if nothing is found. turn off the engine. disconnect all vacuum lines from the throttle body except the line to the MAP sensor and plug the now free ports on the throttle body (you can buy a set of vacuum plugs or masking /duct/electical tape should work for the two minutes you need it to). restart the engine, if idle is normal. plug in the lines one by one to pinpoint the leak. if idle is still high, diagnosis will require more effort and a few special tools(or take it to a shop)

2 days before I got around to following your advice the idle speed took a turn for the worst. Gone is the 2100 rpm and now the engine idles at almost 4000 rpm. It's 4000 rpm on initial start-up, and when the engine is warm, and any time the clutch is pressed. On the road the car does 50mph in 4th gear without having to touch the accelerator. I checked the codes again and none are registered (apart from code 12)?!

So with the engine roaring I sprayed the areas you mentioned with carb cleaner. Apart from when I cleaned the inside of the TB, there was no hint of a drop in rpm's.

Then I moved onto disconnecting the vacuum lines. i saw 4 vacuum lines coming from the TB - (#1) the line to the MAP, (#2) the line to the EVAP CONSTR purge SOL VLV on the block, (#3) the line to the EGR solenoid and (#4) the PCV hose. I didn't touch the MAP line. #2 and #3 didn't seem to want to come away from the TB so, in case they aren't supposed to come away from the TB, I tried to disconnected these lines at the other end. #3 slid off easily. #2 was impossible to access at the block, so I didn't get that line off at either end. #4 came off easily. I taped off the TB ports. Result = no change.

Did you double check that the throttle plate is closing all the way? Maybe the throttle cable is hanging up? Try to close it by hand.

when did it get worse?(driving, start-up, warm, cold, hit a bump?) also it is idling high even at a stop right?

those lines should be able to come off the throttle body, but after time they can get stuck, instead of pulling them straght off, try twisting them or use a REALLY smal flathead srcewdriver or a pick to get them started.

jumper the ALDC again with the engine off. wait 1 minute, then disconnect the electrical connection for the IAC. then start the engine. the IAC should be fully closed

but honestly it would be very hard for a small vacuum line or the IAC to cause a 4000 idle. but there it one vacuum line that can. the brake booster line. it is a thick hose connecting the intake manifold(bottomside i beleave) to the brake booster(disk shape thing the master cylinder is connected to)

if all else fails, post on saturnfans.com

I took the IAC off the TB and saw that the pintle had come off the thread rod and was sitting on top of the intake manifold. I put the pintle back on and started the engine and now the ridle is back down to 2100 rpm. Phew!

Then I repeated the spraying of the vacuum lines - no speed droop.

I also repeated removing the vacuum lines from the TB (the troublesome 2 lines did come off eventually). I didn't remove the line to the brake booster (was that the right thing to do?). Anyway, rpms remained high.

I jumpered the ALDC, waited 1 min, disconnected the IAC plug and then started the engine. The revs immediately just took off and headed to 4000 rpm - this must mean that the IAC is wide open instead of shut - right? This combined with the constant 10.5V at the IAC terminals combined with the fried coil on the replaced IAC valve makes me wonder about the signal to the IAC valve.

No codes register at the moment (but I didn't drive it much after working on it).

Are there any other sensors / switches that I should consider replacing? (The ECTS as mentioned below?).

jumpering the ALDL should have fully seated the IAC(pintle fully extended, pintle valve seat conpletely shut/sealed). reinspect the IAC, see if the pintle fell off again (which may i add i have NEVER heard of happening before :sly: ) if you still have your old IAC compare the two, make sure the part store gave you the right peice. make sure the seat in throttle body is not abnormally worn or damaged, and is clean(carb cleaner again). inspect the IAC O-ring. if it is possible(not sure with the TBI engine) see if you can seat the IAC again(via ALDL) and see if the pintle is making contact with the seat. i have a good feeling we have found the problem area

Problem fixed - idle speed back to normal. It didn't take me this long to fix it, it just took me 4 weeks to get to look at it again.

The clincher? - I replaced the hose going from the pcv valve to the engine-side of the TB.

Why didn't I spot the leak sooner? Two reasons.
1) I didn't follow the advice to the letter. Because the pcv hose was so difficult for me to get off the TB I decided that taping off the engine-end was good enough - bad decision.
2) The leak was at the TB end and was on the underside of the hose, so I hadn't a prayer of getting carb cleaner to it during the line check.

When I did a line check again I decided to put duct tape around the pvc hose and when the rpms shifted down the penny dropped.

So it wasn't the IAC after all.

Thanks to all for the help.

Thanxs for the update.

good to hear indeed, i assume the line cracked or dry rotted?

Ok, I am having the exact same problem. I am going to try sierrap15's method in the morning. I will also probably replace that brake booster line, as it is really soft and looks ragedy. I've done everything else posted on these forums so far. If these last two things don't fix the high idle, I think it's time to let an actual mechanic look at it.

Ok, I am having the exact same problem. I am going to try sierrap15's method in the morning. I will also probably replace that brake booster line, as it is really soft and looks ragedy. I've done everything else posted on these forums so far. If these last two things don't fix the high idle, I think it's time to let an actual mechanic look at it.
Kee[ the faith brother. Give it a try. If it does not work start a new thread and will give you more things to try. Love to see others working. :evillol:

I take it we are all familiar with that nylon/rubber blue hose that everone uses on cold air intakes..... That's what was connecting my TB to the PCV valve. The same thing connects my cold air intake to another metal line coming off the valve cover. I dont know what its called, but both ends of that hose leak oil even with hose clamps on them. I replaced both of those cheap blue hoses with 3/8" fuel line from Auto Zone. Problem is, I neglected to put the hose clamps back on and they fell out of the engine bay somewhere between Auto Zone and my house. So, seeing as how those two hoses aren't clamped and just kind of resting on the connection points... could this have anything to do with the 3k rpm idle?

I'm still going to dissconnect the vaccuum lines and plug the ports one by one tommorrow.

heres a decent shot of how the engine looked before I replace the two blue hoses.

www.cardomain.com/id/saturnstud2000