Avalon cylinders misfiring - Toyota Nation Forum : Toyota Car and Truck Forums

Digi · 05-07-2005, 11:41 PM

I was driving on my way from Boston to Upstate NY. Going up a big hill in New Hampshire, I noticed the check engine light go on. The thing with this Avalon is that it burns up motor oil, so I have to replenish it on occasion, so I pulled on the side of the road, and noticed the oil level to be low, filled it with oil, but it did not stop the light.

So I got off at some small town, and was lucky to find an Autozone, the OBDII gave me the information I needed: cylinders 3 and 4 were misfiring, I believe the code was P0300. Now, the thing is that I didn't notice any difference in the ride of the car - it didnt lose power or even slow down when the light came on, if it wasnt for the light, I wouldn't have noticed anything to be wrong.

I should also say that this happened the last time I made this trip in the end of December, I got the spark plugs changed, all of them, and was told by the mechanic that this was the reason they were misfiring. But I know that spark plugs shouldn't burn out after only ~4 months!

My Avalon is old, 1995 with over 130,000 miles. What I want to know is if it is safe for me to make the drive back to Boston (I HAve to be back on Monday) and get it fixed there. It's about 300 miles from here.

flex-appeal · 05-08-2005, 06:50 AM

I'd guess that it was the misfiring that caused the worn out spark plugs. The mechanic should have looked for the cause of the misfiring instead of just changing them. There are lots of things that could be causing the misfiring, I would suspect the ignition system although its not the only place that the problem could be coming from. Often misfiring is caused by a weak spark or a plug not firing at all. If you are certain that it is only occuring on two of the cylinders then you can rule out the common ignition components, it is likely that it is the individual plug terminals, plug wires etc. Of course, this is assuming that the cylinders are actually sealing properly and are receiving the correct amounts of air and fuel. If any of the conditions are met, the cylinder can't fire properly anyway. There is also the possibility that the last mechanic installed the wrong kind of plugs.
Get it checked out before a long trip, if you absolutely don't have time then just change the plugs and it might (at least temporarily) fix the problem so you can get home and spend more time troubleshooting.

Toysrme · 05-08-2005, 11:06 AM

Blown head gasket. Oil is probably burning on the spark plugs, the carbon deposite left behind are causing the misfire.

Get the compression checked.

OEMonkey · 05-09-2005, 01:05 AM

p0300 is random misfire. if a specific cyl is misfiring(ie cyl 3&4), codes p0303 and p0304 would have come up.
when you take your car to the shop, make sure your oil consumption problem is diagnosed. it might be a massive oil leak or a blowby problem or both. and remember to mention that the vehicle was under heavy load(going up hill) when the mil turned on.

amerikim · 05-09-2005, 08:21 PM

Sounds like mucky plugs. Pull 'em and look.
You didn't say when was the last time you changed oil, plugs or anything.
If its been a while, put fresh plugs in and make sure your oil is topped up, don't overfill to compensate.

flex-appeal · 05-10-2005, 01:00 AM

He said they were changed 4 months ago. Shouldnt get 'mucky' that fast unless something else is wrong