Toyota woes

2001 camry 4 cylinder,auto.

Problem: running rough.

Independent mechanic says a misfire and plugs and wires needed. Dealer says same thing. Both put car on their computer.

So i change the plugs and wires because dealer wants $300. Car is still running rough.

The week before the catalytic converter was replaced.Would this have anything to do with the issue?

Any ideas as i’m at a loss?


How many miles on the car? Are you burning any oil?

Cat converters don’t wear out, they only get contaminated, usually by burning oil. That same burning oil could have contaminated your oxygen sensors, especially the “upstream” one that trims the fuel mix. The test for these is to put them on a scope and look at their output signals.

You may have needed the plugs and wires anyway, especially of you still had the originals on there (?) so I wouldn’t be too hard on the mechanics for this…however if it turns out you needed an oxygen sensor and would like to verbally abuse them for changing the cat converter without looking at the sensor signals, be my guest.

There are a few other things that can cause rough running under specfic conditions such a a sticky EGR valve, but I think a diagnostician is in order here.

Thanks for your reply,
Are you saying that a bad oxygen sensor could be the culprit? It seems strange now, that all this happened after the CAT. replacement.

Yeah, I’m saying you could have a bad upstream sensor. The wire to it could also have been damaged during the cat replacement. I;n also saying the sensors can be tested definitively.

I’m also saying that if the plugs and wires were original you probably needed new ones anyway.

And I’m saying that there are some other causes for rough running, so don;t change any parts until it’s looked at again.

I agree that going off willy nilly and changing things can be very expensive and still not fix the problem.

The car has about 101000 mi.and doesn’t burn any oil.

I have another good mechanic i’m going to have take into his shop next week.

One more question,does this car have coil packs,or some such things? I’m thinking a bad coil.

Problem solved.

It turns out that spark plug wires were mysteriously SWITCHED!!!
I attribute this to mechanic error at shop that replaced the CAT.

Either it was done on purpose to generate more business,or if it was removed to scan for codes,etc. it was not replaced correctly.

In any case i’m up and running.
Thanks for your help.