Following up on this with (hopefully) a youtube video showing my coasting idle issue. I apologize for the terrible and shaky video quality. Audio isn't needed unless you enjoy listening to wind noise. Video shows coasting in neutral from 60 mph to a full stop. AC is on during the coast, but the only difference I've noticed between ac on and off during coasting is the rpm difference once stopped. AC on stopped idle rpm is 100-150 higher than ac off stopped idle rpm. No dtc's set or pending and it's done this since the day 1 of my ownership.

Any insight or help would be greatly appreciated.

2000 Toyota 4Runner 5spd/5VZ neutral coast from 60mph to stopped - YouTube

Doesn't look like an issue to me. My MT Toyotas (previous 3s-fe Camry and 3s-gte swapped Camry) both idle higher while moving and slowly drop just like that when stopped. Probably 900-1000 while moving and ~700 stopped (AC off).

-Charlie

Thanks for your input. It's been in the 1300-1500 rpm range while moving which seems high to me. Compared to the 98 manual I test drove it went to 700-800 rpm when coasting in neutral as soon as I took it out of gear. Sometimes it will go to around 1000 rpm's while coasting down, but most of the time it doesn't. Seems strange to me.

I believe my 1997 does the same as that 1998 you test drove does. As soon as you let off the gas it heads to normal idle. I can't verify it though as I have it still in pieces.



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Sorry this is a little unsteady but it shows the opposite of your experience

Taking R150F out of gear on the freeway - YouTube

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Thanks for the video. It confirms my suspicions, but I have no idea why it's idling high until my road speed drops. My stopped idle (cold and hot) is within spec so that tells me the IAC is good. MAF readings when coasting aren't out of the ordinary. Same with the throttle position. It's a mystery.

Unless the speed sensor [ abs] are telling the ecu to keep the idle above 1k.


What happens when you pull the abs fuse as a test [ besides your speedometer being ] will the engine still hold the higher idle or will it go back down to normal idle position?


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I may be way off base, here, but consider this:

A manual transmission when rolling down the road in neutral may have the propensity, due to internal frictions, to encourage the input shaft to spin, which is then transmitted to the engine through the pilot bearing in the flywheel. This could increase the engine idle during the coasting and would be greater at higher speed.

It's my theory. You should hear about my theory on dinosaurs sometime.

The speedometer gets it's information from the wheel speed sensors from the abs ecu. I don't have any abs codes and my speedometer is accurate. Even if the ecm were looking at the wheel speed it doesn't explain why my rpms are higher than anyone else's rpms (by about 300 rpm) when coasting.

There is nothing coupling the input and output shafts in the transmission when not in gear though. If anything the added weight of the clutch/pressure plate/input shaft/bearing resistances should cause the engine rpm to be lower when the clutch is out and the transmission isn't in gear compared to disengaging the clutch.

Also coasting in neutral with the clutch disengaged completely separates engine from transmission and the high coasting rpms remains.

With the clutch engaged, there will still be some viscous coupling between the input and output gearsets. This happens all the time in MT vehicles - start it with the wheels off the ground in neutral and the wheels will spin (but can be stopped by hand fairly easily). It is a fraction of a hp transferred though, so probably isn't affecting anything here (as proved by the fact that it still does it with the clutch pedal pressed).

I still don't think this is an actual issue though. Disable ABS (and thus the speedo and speed signal to the ECU) and see if it still does it.

Also, watch that video again. The idle speed goes down in even 25rpm increments like every second or half second - it is very well controlled and looks 'planned'.

-Charlie

I don't coast out of gear with the clutch engaged, normally. The video I took is with no pedals depressed.

I can repeat the exercise holding the clutch pedal down.

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Ah.. you did a in gear manual test. I believe this will hold the rpm higher as it does in automatics. Might want to redo your test with the clutch pedal in. Then again with the transmission in Neutral as I expect these 2 results to be the same.. :-)

I'm sorry I was not clear.

R150F trans
Highway driving in 4th gear
Start video
Depressed clutch pedal
Shifted out of gear into neutral
Released clutch pedal
Allowed truck to coast
End of video

I am willing to repeat the exercise keeping the clutch pedal depressed but I rarely do that unless I'm in traffic cause lazy

Any questions?

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To clarify, clutch pedal released is when the clutch is engaged. When you depress the clutch pedal you disengage the clutch. This is ASE definitions by the way. I don’t make the rules. I just take the severely out dated automotive tests. I can’t believe I had questions regarding points and vacuum advance. Ancient technology now in my opinion.

So did removing the abs fuse change anything on your idle issue your trying to resolve?




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