Engine very slow to return to idle

ort5 · Post by **ort5** » Tue Mar 02, 2004 3:53 pm

When I "blip" the throttle on my 91 Turbo 5spd, the revs rise quickly but they fall very slowly. This is annoying to me, and I was wondering if there is anything that I can do about it.

Thanks!

Dave

vrg3 · Post by **vrg3** » Tue Mar 02, 2004 5:20 pm

Is this after the engine has warmed up? That tends to happen much more when the motor is cold.

I can't tell you if what you're seeing is abnormal or not. The engine does take longer to slow down than most of us would probably like. A good solution appears to be a lightened flywheel.

ort5 · Post by **ort5** » Tue Mar 02, 2004 7:19 pm

Flywheel is an option...but I was hoping for something easier and cheaper

It is certainly more pronounced on a cold engine, but it is still quite slow when warmed up. I wonder if it is an ECU thing? I know that sometimes stuff like this is done for better emissions etc.

Thanks,
Dave

evolutionmovement · Post by **evolutionmovement** » Tue Mar 02, 2004 7:57 pm

When cold the ECU slows it down to speed warm up, but when warm it's most likele just the flywheel. Try the older Subarus if you want slow wind down.

Steve

ciper · Post by **ciper** » Tue Mar 02, 2004 8:10 pm

I say flywheel combined with cold idle. Is this your first manual transmisison vehicle?

Kelly · Post by **Kelly** » Tue Mar 02, 2004 8:29 pm

Mine does the same thing. Doesnt matter if its cold or hot, and is intermittant. I know its not a flywheel issue, more like the throttle plate staying open. I oiled the cable, and throttle linkage, but to no avail.

My question is, is there a problem with oil building up inside the throttle body, gumming up, and making it stick? Or is it more likely an ECU issue, or possably TPS?

Id love to just pull off my throttle body, but with my intercooler, its eisier said than done.

Jus curious if any of you have any other ideas, so as to shorten my troubleshooting time

Post by **Legacy777** » Tue Mar 02, 2004 9:27 pm

your TB pretty much isn't messing with your idle too much as long as it's closed. It's your IAC valve.

ort5 · Post by **ort5** » Tue Mar 02, 2004 11:20 pm

This is not my first manual transmission vehicle, nor my first manual transmission turbo, awd Subaru

In checking around under the hood, it seems that my throttle cable is a bit loose, so I will try to adjust it.

Thanks for the help.

Dave

Post by **Legacy777** » Tue Mar 02, 2004 11:25 pm

don't bother messing with your throttle cable. Check the throttle plate and stop screw around the TB. If it's closing fine, then it has nothing to do with the throttle area.

ciper · Post by **ciper** » Tue Mar 02, 2004 11:39 pm

I asked because it is common to notice this when someone owns the first manual after driven automatics. Ive had to explain the difference before.

entirelyturbo · Post by **entirelyturbo** » Wed Mar 03, 2004 6:01 am

Does the idle drop slowly, but steadily? This would be the heavy flywheel problem. As Steve alluded to, EA-series engines are FAR worse about it...

If it is not dropping steadily, then you have an IAC valve problem.

ort5 · Post by **ort5** » Wed Mar 03, 2004 7:19 pm

I would not say the drop is slow and steady. It seems to drop quickly, and then pause at around 2k rpms for around a half a second, and then slowly get down to normal idle (700 rpm or so).

Dave

evolutionmovement · Post by **evolutionmovement** » Wed Mar 03, 2004 7:53 pm

It does sound stuck in cold start.

Steve

vrg3 · Post by **vrg3** » Wed Mar 03, 2004 7:54 pm

It does sound like the IAC valve isn't functioning smoothly. When you let go of the throttle it's supposed to open somewhat to act as a dashpot but it sounds like you're getting too much of that effect. I'd say try cleaning it.

syphon · Post by **syphon** » Wed Mar 03, 2004 10:39 pm

Mine does the exact same thing.

When my engine is cold... if I "blip" the throttle, it'll hang at 2k for almost 2 seconds before SLOWLY coming back down to idle.

biggreen96 · Post by **biggreen96** » Sat Aug 25, 2007 11:37 pm

bump.

After a track day my engine is doing this, when warmed up and is very annoying since I DO have a light flywheel and the RPMs should fall quickly.

I took the magnetic actuator off the IAC and I spun the knob back and forth, it seemed like there was a little stickiness at one end of the play, has anybody had luck taking it off and cleaning it?

Imprezive · Post by **Imprezive** » Sun Aug 26, 2007 8:11 pm

my IAC valve is giving me all sorts of problems, not only does it do the previously mentioned slow return to idle, it nearly kills my car every time I stop at a stop light...

IronMonkeyL255 · Post by **IronMonkeyL255** » Mon Aug 27, 2007 5:18 pm

Mine has an annoying tendency to maintain RPMs when I push in the clutch. It seems I have to wait an abnormally long time before the RPMs drop any.

biggreen96 · Post by **biggreen96** » Mon Aug 27, 2007 8:45 pm

Well I found my problem:

The throttle cable somehow got tighter and wasn't allowing the throttle to close all the way. I loosened the nut that holds the throttle cable by the TB and released some tension and a test drive confirmed the fix.

This was after I spent a while messing with the adjustment of the IAC actuator, which is working just fine.

92ss satinsvoice · Post by **92ss satinsvoice** » Wed Aug 29, 2007 3:03 am

my car has this problem also. ive done a manual swap and my ecu still thinks its aan auto because i havent put a ground wire in one of the pins. (cant remember witch one it is). so my idle will sit around 1100 rpms almost all the time. some times even higher like 1500 or 2000.

im going to try cleaning the iac valve and see if it helps any.

biggreen96 · Post by **biggreen96** » Wed Aug 29, 2007 3:18 am

satin - to avoid taking the whole fucker off which is a pain just take the white cap, the part the harness plugs into, off. If the knob under there can move back and forth easy then it shouldn't need attention.

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Engine very slow to return to idle

Engine very slow to return to idle