Hanging RPMs while coasting in Neutral/clutch pushed in.

This had happened off and on last year but seemed to go away until now. While driving, If I push the clutch in or put it in neutral, the RPMS always hang around 2k. It stays there until I come almost to a stop and then it will drop down to normal idle RPM.

Even if I am say in 5th gear going a little slower so im sitting at say 1.5k RPM, if I put the clutch in, the RPM raises up to 2k. Seems to like 2k no matter what speed I go unless I am under like 5mph or something. Then it will drop down.

Kind of annoying and probably not the best for gas mileage although I have not seen much of an impact yet. I just dont like hearing my engine at 2k while I am coasting to a stop.

What could be causing this? IAC? Something with the clutch? It shifts and drives fine otherwise.

 

I noticed mine does that too.

 

I cleaned the throttle body and MAF last year... Maybe i need to try that again. I never cleaned the IAC valve, so i guess I should get a gasket and do that while I'm at it.

Not sure what else could cause it. Just weird that it only hangs while moving. If I am stopped or moving slow, it does not hang at all.

 

I've noticed this in my truck aswell (V6). Sometimes I'll turn the engine off while coasting, but if i start it again while still moving either by bump or by key, it will still idle high while in neutral MOST of the times. A few times it has gone down back to about 700 rpms. I think it has something to do with keeping the engine up to speed incase you shift up/down. Kinda like how when you're driving and you let your foot off the gas, and then push the clutch, it revs up a bit.

However, this very well could be a moot point depending on what you're trying to achieve. The Tacoma's have something called Deceleration Fuel Cut Off (DFCO). Essentially, while you are coasting IN GEAR, fuel stops being injected into the engine, while the momentum of the car will keep the engine turning. This will apply some additional resistance/braking power. Good when coming to a stop or maintaining speed going downhill. You can read more about DFCO at the link below.

http://ecomodder.com/forum/showthread.php/please-explain-dfco-deceleration-fuel-cut-off-14362.html

 

Interesting...

Just seems weird that It seemed to do it and not do it at times... At least as far as I recall.

Doubt its hurting anything... My MPG still seems good.. (20mpg average).

Still probably go through and give all the goodies a cleaning. Could use it anyways.

 

DFCO would have no effect if in neutral or the clutch depressed since the transmission would be disconnected from the engine.

If the RPM's remain high, it could be the throttle position sensor (TPS).

 

Is that something I can clean? Or test and replace? Why only while moving?

 

Its happens to me (v6, manual) right after a cold start. Appears that once the engine reaches normal driving conditions the rps come down to where they're supposed to be.

 

Mine does not come down after warming up. I drive about 20 miles to work each way and its just the same when I get there.

 

What you are describing is normal for just about every car and helps the engine reach operating temp faster for better emissions. This is not what the OP is describing.

 

Nothing to clean on the TPS other than the contacts maybe but you should test it with a volt meter to see if it's performing within specs.

 

Strange... Did not do it at all on my way home from work yesterday. But I stopped at the store before home and when I went home from there, it did it the whole time (couple miles). I was in the store maybe 5 minutes.

I rode my motorcycle this morning.

 

i have the same problem. i cleaned the iac valve ad maf sensor, didn't change a thing. brought it to the shop and they said they could not fix it because its something with the computer because all the other sensors are operating normally.

 

Thanks for the reply... This is very strange. Would be cool to swap the ECU with another truck and see if it persists or not...

 

Mine did this when I had a bad TPS.

 

I had a corolla 5 speed that did this, try taping the accelerator to jump rpms just a fuzz while coasting. In my Corolla the rpm would drop to normal idle after the bump or if I coasted for longer than something like 30 seconds. Ymmv

Edit. 04 Corolla. No idea if higher rpm is normal

 

This.

Same symptoms for my truck years ago. High revs when in neutral (idling and coasting) and when the clutch would be pushed in.

Replaced the TPS and fixed everything.

 

Mine does this random;y and will drop down to about 800 from 1500 when I rev it. Maybe TPS you think?

 

Finally threw a cel... p0120 throttle position

 

Funny when you are sorta relieved to see the trouble light.
"At least now I know WTH is it."