Wierd Idle/Low RPM ness

[myconid]

I have a 92 V6 auto w/ 125k on it. When it starts up, it revs immediately to 2 grand (almost like the starter is torquing it up that high.. but i let go of the starter immediately), then drops to ~800rpms. Is this normal?

Also, when im doing ~40 on a flat, and let off the gas, the engine drops from ~1.8 to 1.0, then comes back up to 1.2. It also seems to drop out of gear..it makes the slight noise than a 3-4 shift makes.. a little clunk (not really audable.. most 3rd gens ive been in make the 3-4shift noise) or maybe its just the tq dropping lockup? If I press the gas it immediately revs back up to 1.8.

If I turn off O/D, it seems to stay at the higher rev (2.8?), or drop slightly to 2.6. If I slow down to ~30, 3rd gear exhibits the same wierd idle as 4th, and also seems to "drop out of gear".

This doesn't happen if the motor is reving above 2500rpm though it seems.

Any ideas on the wierd idle (I revved it a little in the parking lot, and it goes up to 2000rpm, drops to 800rpms.. every time.. though once or twice it seemed to skip then recover..)

Would replacing the sparks & wires be a good idea?

For kicks I just checked codes.. None

It is also mildly cold out (70's), and rainy. It doesn't seem to be exhibiting the idle wierdness. I only drove to the store and back though (~10 miles). It usually does it from a cold start though, and does it warm as well.

[1GR-FE]

the idle is normal yer RPMs will be higher on start up the IAC valve stays open to allow more air thru the throttle body and as far as yer tranny goes sounds normal too, the trans will always want to upshift to the highest gear possible to increase fuel econ and reduce emissions, so when u give it gas and then let off the trannny will select a higher gear when u switch off the OD then the tranny will stay in the lower gears longer and ur OD will not engage

[myconid]

If im driving along.. minding my own business.. doing 40.. and let off the gas.. sometimes it will go to 1000rpm, to 1300rpm, and back and forth a couple times. Not always, but pretty regularly. Sometimes its just once, rarely it is like 4-5 times.

[bobby769]

Originally posted by myconid
If im driving along.. minding my own business.. doing 40.. and let off the gas.. sometimes it will go to 1000rpm, to 1300rpm, and back and forth a couple times. Not always, but pretty regularly. Sometimes its just once, rarely it is like 4-5 times.

I have a similar problem on my '88 Camry.
The idle jumps up and down a couple hundred RPM around 35-40 MPH.

[gcs118]

Originally posted by myconid
If im driving along.. minding my own business.. doing 40.. and let off the gas.. sometimes it will go to 1000rpm, to 1300rpm, and back and forth a couple times. Not always, but pretty regularly. Sometimes its just once, rarely it is like 4-5 times.

I don't think it's a problem, most, if not all, automatics do that. It seems like the transmission disconnects from the engine when you let off the throttle. This is comparable to disengaging the clutch on a 5-speed. You can usually feel the automatic re-engaging when you push the gas pedal once again.

[myconid]

I don't think it's a problem, most, if not all, automatics do that. It seems like the transmission disconnects from the engine when you let off the throttle. This is comparable to disengaging the clutch on a 5-speed. You can usually feel the automatic re-engaging when you push the gas pedal once again.

The transmission does not disengage when you let off the gas. You can observe this yourself by doing 60, letting off the gas, and watching the tachometer fall, or alternatively drive down a hill, and watch it climb. Even at low speeds it does not completely disengage. Even if it was, the motor should not go back and forth between 1000rpm and 1400rpm, back and forth. That is NOT normal, and no other automatic I have driven it has done it (short list: 1994 Camry LE I4, 1996 Beretta V6, 1991 Supra I6, 2000 Malibu V6, 1995 BMW 525/540i, 1993 Celica, 2001 Subaru Legacy GT, 1989/1992/2002 MR2, 1989/1994 MX6 etcetcetc).

[rezzle]

You really shouldn't listen to me because I am not a mechanic ...


but ....

Its all normal.

The coasting thing is just the electronic control on the automatic transmission trying to figure out what you really want it to do and it takes some time to disengage the torque converter lock etc. Sometimes there is also a small bit of hysterisis between it and the electronic fuel control as well.

The idle reving at startup is also normal just don't assist it by putting your foot on the gas until it evens out.

[gcs118]

Originally posted by myconid


The transmission does not disengage when you let off the gas. You can observe this yourself by doing 60, letting off the gas, and watching the tachometer fall, or alternatively drive down a hill, and watch it climb. Even at low speeds it does not completely disengage. Even if it was, the motor should not go back and forth between 1000rpm and 1400rpm, back and forth. That is NOT normal, and no other automatic I have driven it has done it (short list: 1994 Camry LE I4, 1996 Beretta V6, 1991 Supra I6, 2000 Malibu V6, 1995 BMW 525/540i, 1993 Celica, 2001 Subaru Legacy GT, 1989/1992/2002 MR2, 1989/1994 MX6 etcetcetc).

Ah, thanks for pointing me in the right direction (and not being a dick about it). I drive an auto once every few months, if that. It was just something that I had noticed, how the RPMs would drop oddly...

[Nick]

yeah, my 92v6 also has bouncy idle when i'm coasting, i don't think its a problem

[myconid]

It isnt a problem I guess, its just an annoyance. It seems like sometimes it does it at higher speeds (eg o/d off, doing 50.. doing a lil engine breaking at ~3000rpms around a corner.. and it seems to do the funny idle a little bit.. not alot .. but i can definately feel it modulating). Maybe ill start ripping vacuum lines apart, or replace sparks and such. Its that time anyways.

[bobby769]

Originally posted by rezzle
You really shouldn't listen to me because I am not a mechanic ...


but ....

Its all normal.

The coasting thing is just the electronic control on the automatic transmission trying to figure out what you really want it to do and it takes some time to disengage the torque converter lock etc. Sometimes there is also a small bit of hysterisis between it and the electronic fuel control as well.

The idle reving at startup is also normal just don't assist it by putting your foot on the gas until it evens out.

ok, now i'm confused. You as a nonmechanic are saying that its normal. u tellin me I shouldn't be listening to u?
As a non mechanic, how do u know its normal?

[gcs118]

Originally posted by bobby769



ok, now i'm confused. You as a nonmechanic are saying that its normal. u tellin me I shouldn't be listening to u?
As a non mechanic, how do u know its normal?

he was probably just sharing his personal experience and beliefs, but doesn't want to take full credit if you mess something up :p

[bobby769]

Originally posted by gcs118


he was probably just sharing his personal experience and beliefs, but doesn't want to take full credit if you mess something up :p

i c

[rezzle]

Just trust me

but don't listen to me


Everything you have said happens on most cars with automatics with lockup torque converters and fuel injection.

The reason for the disclaimer is that although this happenstance is 'normal.' I cannot feel how 'severe' a problem you may be having. Who knows you could be feeling a real *clunk* while the rest of us are imagining something we feel everyday.

The dropping out of gear you are feeling is the lock-up torque converter.

You may want to check your fluid level just in case.
Get the car to running temperature, put on the emergancy brake and put the car in neutral, leaving it running check the transmission fluid with the transmission dipstick.