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onlydrive5speedcorollas

2000 Corolla Hesitation/bucking

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Hello All

 

I am a new member. I purchaed a 2000 CE 5 speed 86K miles about two months ago to replace my beloved 89 DX 4-door 230K. The 2000 ran well for month one and developed hesitation under a load. The car will run at 65 MPH however if you back off the throttle for traffic and try to resume, the car hesitates and bucks, Same with accelerating from a stop or pulling a hill. Need to wind out the gears otherwise car bucks if you shift as normal. No CEL to date. I have done the folliowing: pulled plugs, car has correct NGK, all look fine and consistent. Air filter is like new, I cleaned the TBI, mass a/f, PCV and OCV filter per the helpful DIY by Fishexpo. TBI was pretty dirty, toothbrush black, OCV filter was clear except for oil as expected. I tried a bottle of dry gas and STP fuel injec cleaner. No real improvement. I hear a hissing sound near the intake, however co-workers Corolla sound exactly the same with no drivability problems. This car came from a Ford dealer as a trade so I have no repair records. Car appears to have been cared for. Any suggestions and will the ECM register a code if no CEL is triggered. I know the causes are endless, however I am up for advice and typically pretty handy(two timing belts, head gasket brakes etc while owning the 89 DX for 10 years, and timing belt on wife's 2000 CRV last weekend, outside with no compressor, 25 degrees without the wind chill).

Edited by onlydrive5speedcorollas

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trap

Hard to say, as you've already touched upon most of the other possible culprits (OCV filter, MAF sensor, TB, etc.) - could be an electrical/ignition related issue (coil is overheating/electrical load), bad injector (sticking), or vacuum leak somewhere.

 

Have you noticed if the hesitation is keyed to a specific throttle position (i.e, 1/2 throttle, 1/3 throttle, etc.) or a set RPM, RPM range?

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Hard to say, as you've already touched upon most of the other possible culprits (OCV filter, MAF sensor, TB, etc.) - could be an electrical/ignition related issue (coil is overheating/electrical load), bad injector (sticking), or vacuum leak somewhere.

 

Have you noticed if the hesitation is keyed to a specific throttle position (i.e, 1/2 throttle, 1/3 throttle, etc.) or a set RPM, RPM range?

 

thanks in advance, hesitation happens from second gear on basically during acceleration or when attempting to resume speed. Car wil cruise at 65 MPH no problem, but if you back off and pick up again, problem is there. I forgot to mention that I ran it somewhat low on gas just before problem started. Low fuel light never came on, but was down to 1/8 tank or so. Bad idea I know. Should plug wires/coil be changed at certain intervals. My 89 had a regular cap/rotor so this set up is new to me.

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If you consistently run on a low tank, that might be a problem - could have pulled in some water into the system, that could be causing some misfiring, but the Gas-Dry stuff should have cleared that up.

 

The iridium plugs are designed to be good for 120K miles for typical driving, though some have seen extensive electrode wear at 80K-90K. Coil on plugs do not have specified replacement interval - just replace when they go bad.

 

For this hesitation/stumbling on acceleration, this can be caused by the following:

 

- fouled or stuck fuel injectors

- faulty MAF sensor

- faulty IAT sensor (same module as the MAF)

- faulty TPS sensor on the TB

- excessively worn spark plugs

- dying coil

- low or inconsistent fuel pressure (possible leaky fuel pressure regulator or weak fuel pump - both are part of the fuel pump assembly and inside the gas tank)

- vacuum leaks (possible sources are vacuum hoses, vacuum t's, intake manifold, throttle body, brake booster)

- bad tank of gas

- bad O2 sensor (upstream, pre-cat)

 

Since you can get up to cruise and it only stumbles afterwards, I'd suspect a vacuum leak or possibly a bad O2 sensor. Bad or dirty MAF is the usually culprits in this case, though since you didn't see a significant difference after you cleaned it - unlikely it is the cause. Bad TPS sensors are very rare, but can happen. Also given that is seems to happen on a heavier engine load - I'd also check the serpentine belt and alternator - as the 1ZZ-FE is very sensitive to electrical noise. Slipping belt or noisy alternator will also give this hesitation behavior.

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Thanks for such a detailed reply. I am pleased to report that my problem was resolved via simply adding a bottle of Chevron Techron to the tank. It is two weeks post Chevron and the vehicle is back to 100%. Perhaps a gummed up injector as suggested. In any event, I still believe that the TBI/OCV/PCV DIY is great preventitive maintenance. Great tips and photos on that.

 

 

 

 

 

 

 

If you consistently run on a low tank, that might be a problem - could have pulled in some water into the system, that could be causing some misfiring, but the Gas-Dry stuff should have cleared that up.

 

The iridium plugs are designed to be good for 120K miles for typical driving, though some have seen extensive electrode wear at 80K-90K. Coil on plugs do not have specified replacement interval - just replace when they go bad.

 

For this hesitation/stumbling on acceleration, this can be caused by the following:

 

- fouled or stuck fuel injectors

- faulty MAF sensor

- faulty IAT sensor (same module as the MAF)

- faulty TPS sensor on the TB

- excessively worn spark plugs

- dying coil

- low or inconsistent fuel pressure (possible leaky fuel pressure regulator or weak fuel pump - both are part of the fuel pump assembly and inside the gas tank)

- vacuum leaks (possible sources are vacuum hoses, vacuum t's, intake manifold, throttle body, brake booster)

- bad tank of gas

- bad O2 sensor (upstream, pre-cat)

 

Since you can get up to cruise and it only stumbles afterwards, I'd suspect a vacuum leak or possibly a bad O2 sensor. Bad or dirty MAF is the usually culprits in this case, though since you didn't see a significant difference after you cleaned it - unlikely it is the cause. Bad TPS sensors are very rare, but can happen. Also given that is seems to happen on a heavier engine load - I'd also check the serpentine belt and alternator - as the 1ZZ-FE is very sensitive to electrical noise. Slipping belt or noisy alternator will also give this hesitation behavior.

 

 

 

 

 

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So I am back again. My hesitation/bucking returned after about three weeks/800 miles of use. I added another bottle of Chevron/Techron and, once again noticed a big improvement. Now the symptoms are back again about three weeks later. I believe the problem is now narrowed down to fuel and not spark. I removed the rear seat and pulled the fuel pump/sender. The fuel strainer is not plugged. I did not notice any sediment and the pump draws from a small "basin" within the tank. The basin and fuel in it looked immaculate. Anyone have experience with injector cleaning both commercial or DIY?

By the way, there is a obvious miss at idle speeds, thanks

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If the Chevron additive made a markedly difference in idle quality and driveability - I'd suspect that either your injectors are very dirty or there is a significant amount of carbon build up inside the combustion chambers. A professional injector service - where they disconnect the fuel line and run the car off a pressurized bottle of solvent + fuel, might solve your issue.

 

Another possibility is one of the injectors is sticking or starting to fail on you - may just be running the additive with better operation is just a coincidence. Could try adding a couple of ounces of Marvel Mystery Oil (~4 ounces should be plenty) to a full tank of gas and see how it runs. Its an old trick on carburated cars that does seem to work on some fuel injected applications - supposed to "lube" the injectors. Not sure if I believe that, but it is a decent solvent and a decent fuel stabilizer and can dissolve gum/varnish that some fuel injector cleaners cannot remove.

 

Also track the mileage with and without additives, and see if there is an appreciable change. Could be something else that is causing this stumbling/missing at idle/off-idle speeds that may not be fuel related.

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After reviewing my options, I chose to have the on-car fuel injector/decarbon service at a local Firestone. I prefer to do my own work, but had this done professionally. So far so good as the hesitation is gone and the car did really seem to benefit from the service. It is a little costly at $99.00 plus tax/fees, however it appears to be an advantage if you plan to keep the vehicle for some time.

Thanks for the suggestion.

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After reviewing my options, I chose to have the on-car fuel injector/decarbon service at a local Firestone. I prefer to do my own work, but had this done professionally. So far so good as the hesitation is gone and the car did really seem to benefit from the service. It is a little costly at $99.00 plus tax/fees, however it appears to be an advantage if you plan to keep the vehicle for some time.

Thanks for the suggestion.

 

 

onlydrive5speedcorollas,

 

My sister-in-law just purchased and '01 Corolla S w/5spd and it's displaying the exact same scenario the you've described in this thread. I'm just curious if yours is still running well after the professional flush?

 

Thanks,

-rob

 

 

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I was having similar symptoms and it ended up being my o-rings on my injectors (fuel rail side). I replaced them, and works like newish again. just FYI.

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I was having similar symptoms and it ended up being my o-rings on my injectors (fuel rail side). I replaced them, and works like newish again. just FYI.

 

Alex, Was there a noticeable leak on your car? thanks, -rob

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sorry for the delay in my reply. The professional fuel system cleaning cured the problem for a few days. The car has been hesitating ever since. My car has a miss that you can notice while stopped at a red light. You feel it in the car. My mileage just hit 100,000. Otherwise, the car has been super. My next step is to check fuel pressure, however I need to obtain stuff so my current gauge will work. thanks

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Hmm. Given that this has been pretty persistent and "seems" to be improved with fuel treatments - I'd start suspecting the pre-cat O2 sensor. Some people have been able to get some mega-mileage and lifespan from the OEM sensor, others had them go bad as early as 30K miles. This is more likely, if the car does this after it reaches operating temperatures. Though fuel economy generally starts to nose-dive at the same time as well.

 

Otherwise, I'd suspect dying injectors or dried out o-rings by the injectors/rails, sucking in air. If you are able to get OBD-II data logging while the car is operating, it might be able to shed some light on what the car is doing. This is more likely in cases where the fuel economy hasn't really changed that much from before - injectors are leaking extra air past them, leaning out your air/fuel mix. Can tries to compensate by increase injector duration - but if they are already jammed up on their duty cycle and don't have any more headroom, misfiring and stumbling will usually result.

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Hmm. Given that this has been pretty persistent and "seems" to be improved with fuel treatments - I'd start suspecting the pre-cat O2 sensor. Some people have been able to get some mega-mileage and lifespan from the OEM sensor, others had them go bad as early as 30K miles. This is more likely, if the car does this after it reaches operating temperatures. Though fuel economy generally starts to nose-dive at the same time as well.

 

Otherwise, I'd suspect dying injectors or dried out o-rings by the injectors/rails, sucking in air. If you are able to get OBD-II data logging while the car is operating, it might be able to shed some light on what the car is doing. This is more likely in cases where the fuel economy hasn't really changed that much from before - injectors are leaking extra air past them, leaning out your air/fuel mix. Can tries to compensate by increase injector duration - but if they are already jammed up on their duty cycle and don't have any more headroom, misfiring and stumbling will usually result.

 

 

Funny you should mention the car reaching operating temperature. I only notice the miss after the engine has reached operating temp. Maybe the idle is higher when cold, however the miss is obvious only after driving for several blocks. Seems to be worse during damp weather. I assume that the pre-cat 02 sensore is located in the manifold? Also any way to test it other than buying new? I have a multi meter. by the way, no CEL light to date.

 

One other thought worth mentioning. I pulled the plugs about a week ago to check for normal wear. #1 plug wire/coil appears to have been changed by a prior owner. It was cast differently than the other 3 and had obvious aftermarket numbers and markings. The hex of the plug for #1 had this red dust and corrosion as if removed from a lake. The other three plugs were fine. I suspected heavy resistance. I cleaned the mounting surface of the head, however no improvement in performace was noted. The car is not a rust bucket and has little underhood corrosion. Something to ponder.

 

thanks again

Edited by onlydrive5speedcorollas

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You can "backprobe" the O2 sensor to check its operation. Trying to measure resistance over the sensing element with a multimeter can damage the O2 sensor. For this generation - the pre-cat O2 sensor is on the front exhaust pipe, between the bottom of the exhaust manifold and the pipe leading to the catalytic converter. Kind of a pain to get to - might have to attack it from above with some long socket extensions and wobble joint and if you have larger hands/arms - below if you have smaller hands/more flexible. I'd also visually inspect the connection and the wiring to the O2 sensor. Possible that the sensor is fine, but the wiring is either shorted out to ground or there is corrosion inside the connector.

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