Corrolla loss of power during acceleration

My 98 Corolla looses power (RPM’s) upon acceleration. The power loss varies from barely perceptible to so bad I have to pull off down a side street to get out of traffic. It happens pretty randomly (don’t see a real pattern) but seems to be more noticeable on more rapid acceleration. An O2 sensor was recently replaced. It has 96k miles and is due for a timing belt replacement.

I wonder what are the most likely causes in part to determine if it’s worth the money to replace the timing belt or is the car on it’s last leg?

Any ideas on what to do?

You need to say some things about the basic maintenance - like what has been done lately and what is up to date. The places to start for all problems like this are the basics - fuel filter, air filter, plugs & wires. After that checking fuel pressure wouldn’t be a bad idea.

Is the “check engine light” on?


Until the car is brought up to date with basic maintenance, it is not easy to “cherry pick” any one source of this problem. Once it is brought up to date with maintenance, the problem may go away, or at least it will be easier to diagnose.

Incidentally, the car is not due for a timing belt replacement.
It is actually grossly OVERDUE by about 3 years.

Take a look at the Toyota maintenance schedule (it should be in your glove compartment, probably inside the Owner’s Manual), and you will see that there is an elapsed time limit for all maintenance procedures, in addition to the odometer mileage limit, with the proviso, “whichever comes first”, as in “X miles or X months, whichever comes first”.

Despite the relatively low odometer mileage on this car, it was definitely due for the very vital replacement of the timing belt by 2006, at the latest.

Time to read the Owner’s Manual!!

I do read the owners manual, perform regular maintenance,and I am not asking anyone to cherry pick. I did not own the car in 2006 for all I know the belt has been changed but I can only assume it has not. I am simply asking for possible answers. According to what I have read so far any problem there may be with the timing belt would not cause this problem the car is now having.

So, I would still appreciate an answer to the question of what may cause the loss of power problem.

Thank you.

A tune up was performed last September after which gas mileage dropped a bit so I had them look at it again. They double checked their work and added seafoam to the car. Immediately the check engine light came on. That is when the O2 sensor had to be replaced (by another mechanic). After that is when the problem with loss of power started. The fuel filter I’m told is designed to not need regular replacement. It is part of the the fuel pump inside the tank. The air filter is fine. The check engine light is not on.

Fuel pressure. Interesting. Is that something a mechanic must do or is that something anyone can do?

Thank you.

No matter what anyone told you, the fuel filter does need to be replaced on a regular basis, preferably every 30k at most. When an engine is run for an extended period of time with a partially blocked fuel filter, this can lead to early failure of the fuel pump.

So, if everything else listed in the Toyota maintenance schedule is up to date (with the exception of that ignored fuel filter), then I would strongly suggest that you have the fuel filter changed. If that does not help, then you may need a fuel pump, but to save on labor in the long run, have the fuel pump’s pressure tested when the fuel filter is replaced.

And, since you acknowledge that you don’t know whether the timing belt was replaced or not, you have to assume that it was not. When that belt snaps, major engine damage will take place, so I would suggest having that job done a.s.a.p.

Fuel pressure testing is generally easy and not expensive if you ask someone to do it. For about $40 you can also pick up a pressure gauge and learn to do it yourself. It may be best to rig up a relatively long hook up for it, run it out & tape it to the outside of the windshield so that you can have a helper watch its behavior as you test drive.

Of course, with all of that new info about problems starting after a tune up and O2 sensor I really wonder whether or not there was a problem there somewhere. What does the mechanic say about the accel problem?

You should also listen to VDC and do something with the fuel filter. It also couldn’t hurt to clean your MAF sensor. (The tune up didn’t include a K&N air filter did it?)

I regret to inform you that your Corolla 1.8L engine ain’t got no timing belt. Hits got a timing chain, which will outlast the rest of the engine.

I would double check to make sure the correct ox sensor was used.

Can you start it right back up when it stalls?

It could also be the ignition module. Does the tach act erratic when it stumbles?

It could be the ignition switch. Try wiggling the key when it acts up.

Could also be fuel pump relay or fuel injector ballast resistor, if it has only one, vs one for each injector.

I didn’t say it stalls. It looses RPM’s.

I will look into the fuel filter issue again. Someone also suggested the mass air sensor which I will also look into.

I will.

What do you mean you wonder whether or not there was a problem? Before or after the O2 sensor?

The mechanic has not been able to duplicate the problem. It is intermittent. The weather is getting warmer here and it seems to be doing it less and less. Someone told me it takes a few miles of driving (50-100)after something like an O2 sensor is replaced for the engine to ‘reset’ itself. This sounds goofy to me. Beside that it’s been several hundred miles.

I will look into the MAF sensor. Never heard of that before. No the tune up did not include and air filter.


The engine doesn’t have the power to accelerate. That spells lack of fuel being injected into the engine. This problem requires a little understanding of what controls fuel flow (injection) and how it’s done. This is rookie mechanic kind of stuff; yet, no one seems to understand it. A pity.

Check fuel pressure AFTER the fuel filter has been replaced. A dirty fuel filter drops fuel pressure and flow rate. Here’s how the fuel filter is replaced:

Checking fuel pressure is more than just attaching a fuel pressure test gauge to the fuel line. Since the problem is acceleration, do the fuel pressure test at acceleration, as stated by Cigroller. Tell me, how else can you tell if the fuel pressure is what it should be?

After you get the actual operational fuel pressure, we can talk about signal inputs and signal outputs which involve fuel flow.

This is an awesome link. Thanks!
I will look into the fuel filter issue/replacement and bookmark the link you gave for use in the future as well.

P.S. Interesting that the mechanics at the local Goodyear Gemini shop (they installed the O2 sensor but have NOT been doing the later diagnosis) said the fuel filter was part of the fuel pump as is not designed to be replaced as it is in the gas tank! Considering some of the other things they have told me that turned out to be wrong it appears they are not very knowledgeable or trustworthy. Again thanks for the info.

Hey Buddy,
Do you notice any foul odor coming from exhaust or smell it in car? (Other than leaving Taco Bell) Now when you do accel., does it bog down completely or does it tend to miss, lurch, shudder, etc. I’m beginning to suspicion Catalytic Converter.
Hope we’re getting you somewhere.

No odors. It just looses RPM and slows down. Sometimes if I let up on the gas and push down again it breaks free but only sometimes. no missing, lurching, shudders… The catalytic converter was checked when I had the transmission checked (almost forgot about that).
Thank you

The Mass Air Flow sensor is a fairly expensive one, and probably NOT the problem. The ODB-II system is fairly sophisticated, and would have flagged that sensor if there was a problem. However, the ODB-II system does not monitor fuel pressure, only the feedback from the injectors. And will only trigger a fuel injector problem if it gets eractic feedback signals. This does not include fuel injector flow rates. Dirty injectors also cause this problem, and may not set a code until the problem gets much worse. I suggest you get a diagnosis done before throwing parts at it. Throwing parts gets to be very expensive quickly.