I have a Toyota Corolla LE 1.8L with 250,000 miles. Recently, I started having issues with acceleration and rough idling. After stopping the car, most of the time it does not accelerate and suddenly it picks up acceleration. I had the mechanism take a look at the MAP sensor, Throttle body, and Fuel Injector. All seems to be fine. The Air filter is a little bit dirty but not too bad. I will be replacing it soon. I am running out of ideas as to what could be going wrong.
I connected the OBDII meter and looks like the Short fuel trim seems to drop immediately when the issue happens.
I really appreciate any help in providing some advice on how to diagnose and fix the issue.
Thank you.
It seems the throttle body is acting up but if you can hook up a scan tool and record the data when the car acts up, that helps you a lot in finding the issue.
It would be helpful if we knew the year of the vehicle plus the actual codes and fuel trim readings. Aside from the air filter how old are the spark plugs and fuel filter? Fuel pressure OK?
Thank you. The year is 1999. I forgot to mention, I replaced the spark plugs. The short fuel trim readings used to go up to 10 and suddenly drop to 0 even when I had the gas peddle completely pressed. I can try to get more accurate readings and provide an update.
I was planning to replace the fuel filter next. How do I check fuel pressure?
How do I check fuel pressure?
You check fuel pressure with a fuel pressure gauge. I'm not sure if that's one of the tools that parts stores loan out but you could look into it.
Your symptoms are classic for a clogged fuel filter and/or low fuel pressure but the car is obviously quite old (nearly 1/4 century) so anything goes. At that age and mileage it might not be a bad idea to do compression and leakdown tests to verify internal engine condition. It would also be a good idea to check for vacuum leaks.