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2001 Corolla POOR performance PLS HELP




Guest HateMyToyota

When I hit the gas the car actually drops in RPM (250-500 RPM drop) before climbing. This problem occours in neutral as well as in drive and at any RPM range. If the car is at rest on any type of incline and I hit the throttle the RPM will drop to 500 and stay at 500 even with 100% throttle. The car will stay stationary or roll back. I can get it moving if I use the brake to build torque.

From 1250-4000 RPM the car feels normal as long as i keep my foot on the gas. Above 4000 RPM I have a serious loss in torque even at 100% throttle the car may shift 1500 RPM short of normal i think due to low torque.

I have changed the air filter and cleaned injectors. The check engine light is on and stays on, it just came on though and the problem has been going on for a while. The car has 36K and always maintained according to dealer specs.

Thanks to anyone who can help!!!

Right now, your Toyota hates YOU, because she's telling you there's a problem in the only way she knows how-- by the "Check Engine" light-- and you are ignoring it and just trying to modify your driving style to work around the problem.

You need to hook it up to a code reader to find out what the problem is. Your dealer, or a competent mechanic with a well-outfitted shop, can do this for you.

Could be a bunch of things causing the engine "bogging" that you describe. Depends on how many miles are on the car, last tune up, maintenance schedule, etc. Was this happening ever since you got the car? Or was it something that just popped up or happened over time. Simple things to check out:

- possible restriction in the airbox or filter not correct for vehicle

- check condition of spark splugs - if in doubt, replace them

- could be bad O2 sensor

- could be bad throttle position sensor

- could be a plugged fuel filter (hard to get to - it is in the tank)

- could be a slipping transmission (has it been changed?)

- could be faulty VVT valve (long shot, kicks in at 4200rpm - but some early models had pin wear on the VVT pulley assembly giving poor high rpm performance)

If you haven't had a tune up or don't remember when you did the last one - good tune up will cover all the normal maintanence issues that might cause this behavior. AlaricD has a good point to get you car's OBDII scanned for trouble codes. A check engine light will not tell you the severity of the problem at hand - usually having it come up is not a good sign - if the above checks out OK be prepared to spend some $$$.

Good luck.

Guest HateMyToyota

Thanks for the info! The check engine light just came on yesterday so I am not really ignoring it but in all honesty I did ignore the previous symptoms and I really should know better. A ~little~ knowledge proves to be a dangerous thing.

I checked the air box for obstructions and the MAF looks good but what do I know.... I double checked and the filter is correct, clean and new.

Plugs/wires appear perfect but I have no exp. w/iridum.

O2, TPS or fuel filter are good to hope for i guess and the scan should reveal a problem there if I am not mistaken.

Slipping tranny hmmmm....could that bring the RPM down to 500 under full throttle and allow the car to roll back?

I think VVT could only be a secondary problem.

I have an appointment tomorrow morning to pull the code and I will report the results tomorrow evening.

Thanks again.

Guest HateMyToyota

Trouble code came up as PO172 system always rich.

O2 sensor tested OK no problems found with fuel delivery filter or injectors.

What am i missing?

Well you got it narrowed down - PO172 a rich mixture points to thses common problems:

- MAP sensor output faulty

- Injector damaged of faulty

- Fuel pressure out of spec

- Intake air leaks

- Vacuum leaks or missing/damaged hose(s)

- Heated oxygen sensor (one before the cat)

- Adjustment need to AFC (air / fuel controller)

Most likely culprits are the O2 sensor, ignition problem, and/or vacuum leaks.

Most should show up under the OBDII scanner. Also, unfortunately, codes may not point to the same thing from manufacturer to manufacturer.

A slipping tranny may be the culprit - but it sounds more like an engine bogging problem (getting too much gas or not enough air).

Iridium plugs are supposed to run 100-120K miles without needing to be replaced. Like you said - plugs look perfect - I wouldn't change them.

Longshot - O2 sensor will still read "good" if in open loop mode or has an offset bias voltage (applied when O2 sensor is not up to working temperature range). If the scanner doesn't pick up on this - it will measure an "invalid" voltage, but will not register a "fault".

Hope this helps. Good Luck.



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