I have a 98 Camry 2.2L. About a week ago it started to hesitate intermittently when the accelerator was pressed. I added injector cleaner with the last fill up, and cleaned and re-gapped the the spark plugs (plugs and wires were replaced one year ago). This did not help.
I then had the error code read at Autozone, and was told that cylinder 1 and 4 were misfiring. I replaced the coil that feeds 1 and 4, but it still has not fixed the hesitation.
I haven't gone down the path of cleaning the throttle body or it's related parts yet, because it seems to me that that would effect all 4 cylinders and not just 1 and 4. But if new plugs don't help out, I'll do that next.
I have to agree that it could simply be those 2 spark plug wires, especially if you replaced them a year ago with an aftermarket set. Remove each wire and check the resistance with a digital volt/ohmeter. You shoudl get about 25,000 ohms max. Don't be surprised if you can't get any reading. That means there is an open circuit; in other words, a break inside the wire.
Agree with Mike above. Problem with 1&4 would lean toward a coil/spark plug wire/spark plug issue. Don't worry about other things yet. Make sure your ignition system is working properly before moving on.
I pulled the #1 spark plug wire while the engine was running (which I had done earlier too), but this time I rev'd the engine at the same time and saw a spark arcing between wires 1 and 4 just above the boot on the coil end of the wire.
They were still under warranty, so a got a free replacement set of wires, but I think I'm gonna get an actual Toyota set this week.
I had a professional tech once tell me that cheap plug wires last about a year. If you plan on keeping the car any length of time, bite the bullet and go with the Toyota OEM's.
Another thing I like to do is to keep old parts that I have replaced as maintainance in an old bin. That is, if I know they were still functional, but replaced as part of general maintainance. They make good test parts if something goes wrong down the road. Old plug wires, if they were good when replaced, would fall under that category.