Weird behaviour of my Camry 2000

[dimabor]

Hi everybody!
My first post here is inspired by weird behaviour of my V6 Camry CE. It showed for the first time last winter. I have this car since September 2007 so I do not know how long this problem exists.
The symptoms are as following: time to time something happens to my car and it delays with shifting gears, upshifts and downshift. When I'm just starting the car after traffic light for example I accelerate very gently but RPM goes up to 3000 on hot engine and only then upshifts to second gear (without this problem it usually upshifts at 1600-1800). Same picture with shifting from 2-nd to 3-rd. When I slow down downshifts are delayed too and before shifting from 2-nd to 1-st gear RPM drops dramatically and engine tends to stall. One more thing: when I drive on some street with a lot of stop-and-go's after coming to full stop and depressing accelerator engine stalls for the moment but then returns to life again. Not after releasing brakes when car slowly starts moving but just after gentle depressing of accelerator. Delays with upshifting have one more interesting detail: no matter how I do accelerate upshifting will take place after some period of time. I mean I can push accelerator and rise RPM to 3000 and higher or I can accelerate it to speed at which upshift usually happens and then ease my foot from pedal - shifting will trigger after 'n' seconds in both cases. Seems like there is some timing device which doesn't permit upshifting until 'n' seconds over. Also switching from Parking to Drive or to Reverse is significantly harsh - car jolts back or forward and I'm starting to worry about my tranny, it won't last long after such hits.
This behaviour might start at any time and last for half an hour or several days and then spontaneously disappear. Also may be this is just coincidence but I noticed several times that if after I turn the key to ON position and right away start the engine - it starts roughly, RPM very low and the problem I described above is very likely to appear. If I turn the key to ON position, wait for 5..7 seconds and only then start the engine - it starts normally and, if I don't currently have that problem, it's unlikely to appear after such delayed engine start. ECU needs time to warm up?
As I said this problem started to show last winter, more precisely with first cold days. Most of the winter time I had this problem and I thought that this might be related to ATF (too high viscosity when cold). With warm weather this problem has disappeared but just recently returned back in pretty warm days.
I read error codes and sensors data with scan tool. Two error codes were recordered - P0120 (throttle position sensor "A" failure) and P0446 (evaporative emission system vent control circuit failure). Sensor data do not show anything extraordinaire, regular values. MIL light should be on but it isn't - bulb burned out? :-) Or dealer cut off the wire?
Somebody experienced same problem? Or maybe somebody can point out the problem based on symptoms?
Please anybody give me some suggestions.
Great thanks!

[kocho]

Did you check the tranny fluid level? If low it can do similar things and not shift properly...

[dimabor]

Originally Posted by kocho

Did you check the tranny fluid level? If low it can do similar things and not shift properly...

Thanks for the answer. Yes, I checked ATF level with running engine - it is between upper (hot) marks. ATF doesn't smell burnt, color is not brand new pink but satisfactory (pink and just a little bit brown).
Could this problem be related to wrong data from throttle position sensor or defective accelerator cable (the one that goes from throttle body to tranny)?

[Kep]

Did you check to see if there were any error codes for the transmission?

You mentioned that even though you are accelerating slowly the car will go up to 3000 RPM. Do I understand that it is accelerating uncontrollably (and rapidly) to 3000 RPM or is it accelerating up to 3000 RPM in direct relation to how you have the gas pedal depressed but it is just not shifting until 3000 RPM?

I think you really should have it evaluated by an honest transmission shop.

Luck,
Kep

[dimabor]

Originally Posted by Kep

Did you check to see if there were any error codes for the transmission?

You mentioned that even though you are accelerating slowly the car will go up to 3000 RPM. Do I understand that it is accelerating uncontrollably (and rapidly) to 3000 RPM or is it accelerating up to 3000 RPM in direct relation to how you have the gas pedal depressed but it is just not shifting until 3000 RPM?

I think you really should have it evaluated by an honest transmission shop.

Luck,
Kep

Thanks Kep,
the car accelerates in accordance with the effort I apply to gas pedal, but with that gentle effort I apply I expect upshifting at 1600..1800 RPM but the RPM continues accelerating up to 3000 and only then upshifts. Or, as I said before, I accelerate it to 2000, then ease my foot from gas pedal, car rolls and then after 2..3 seconds upshifts.
Check the tranny is good idea, I thought about this too but why the engine stalls sometimes when I press the gas when starting after full stop?

[Hajoca]

I had to replace my V6's TPS in early 2004.

There is two ranges of resistance signals that the TPS will report to the ECU/ECM, and what you describe is the ECU is thinking that you are pressing down on the throttle heavily even though your not.

I recall the part was about 75 CDN and 5 minutes to replace.

The 0446 is a vacuum switching valve that is probably corroded and seized now, but is not going to affect drivability that you describe.

[Kep]

I believe that you have multiple problems here. I understood that you had the two error codes (P0120 & P0446) but I hadn't understood that the engine was sometimes stalling.

When you first turn the car on it activates all of your dash error lights to allow you to determine that the lights work. The MIL/CEL light should momentarily come on at this time to reassure you that it is (or is not) working. If it does (as I suspect it will) then the wires have not been cut and the light is operational. If the light works but it isn’t flashing yet the ECM may not have gotten enough error hits from the sensors to warrant flashing the MIL/CEL yet.

The shifting points and hard shifts still seems like transmission to me.

The stalling and rough starts are likely unrelated and likely a result of a problem with the EGR system and/or the throttle position sensor. I think I would clean out the EGR first and see if you can clear the errors. It wouldn’t hurt to go ahead and clean the throttle body and squirt some cleaner in the IAC valve as well. If the PO120 code still comes on then you’ll need to troubleshoot the throttle position sensor system as well.

If a trany shop suggests that you replace or rebuild the transmission I might consider changing the transmission fluid, flushing the transmission or using a transmission fluid additive to see if it helps first. (The worst case scenario is that it messes the transmission up more but since you’ve been told to replace it anyhow you will only have lost the expense of what ever treatment(s) you select.) There are several out there that say they help to prevent hard shifts. My 1990 had a similar problem and I just got very adept at letting up on the accelerator in order for it to shift softly where I wanted it to shift. It never got bad enough for me to want to take it in for evaluation.

Sorry that I don’t have more definitive answers for you.

Kep

[dimabor]

Thank you guys for the answers and suggestions. I'll add them to my armoury.