99 Avalon Engine Miss

[bgust]

I have a 1999 Avalon which develops a bad engine miss after driving 20-30 miles on the interstate above 60mph. There are no check engine lights or codes, but the dealer replaced the plugs and wires. This did not fix the problem. After the engine begins to miss, it will run rough, even at low speeds until the engine is turned off. The dealer is clueless and won't drive it long enough to reproduce the problem. Anyone know what can cause this?

[artrip36]

Originally Posted by bgust

I have a 1999 Avalon which develops a bad engine miss after driving 20-30 miles on the interstate above 60mph. There are no check engine lights or codes, but the dealer replaced the plugs and wires. This did not fix the problem. After the engine begins to miss, it will run rough, even at low speeds until the engine is turned off. The dealer is clueless and won't drive it long enough to reproduce the problem. Anyone know what can cause this?

a 99 avalon only has 3 wires that feed the back 3 cylinders. the front 3 are powered by 3 seperate coils. these coils are pretty common to go out. so are injectors on a 1mzfe v6. most misfires will cause your check engine light to flash and store a diagnostic code in the ecu. tell the dealer to look harder.

[chadsosne]

artip36, do you know ofhand what error code this problem produces?

[artrip36]

Originally Posted by chadsosne

artip36, do you know ofhand what error code this problem produces?

a general misfire will produce a code P0300 which says random/multiple cylinder misfire. codes p0301,p0302,p0303,p0304,p0305,p0306 all pertain to a specific cylinder, 1-6

[pinkflydxx]

Not sure if this is same problem I had on a 99 Avalon, but after running on interstate for a while at high speed, would get a "miss" - actually a very rough idling condition. Ran "ok" at higher speeds, but when slowed down or stopped - terrible idle.

However, after car cooled off, it ran fine, until engine got somewhat hot again, then same problem. During all of this, it never once threw a check engine code. I checked out numerous items on the car. Finally I took off the EGR valve and cleaned it thoroughly (numerous times) with thottle body cleaner, and worked the spring up and down a lot during the cleaning process, and viola' - no more problems since.

Some other recommendations of items to check (I received from other people):
1. Check vacuum lines for leak
2. Check air intake for cracks
3. Clean MAF sensor
4. Clean throttle body
5. Check throttle body position sensor
6. Coolant temperature sensor
7. PCV Valve
8. Idle Air Controller (not a cheap item)

Good luck and I hope this helps.

[papirringo]

if you have any problem with sensors, you are going to have a code, either a hard code or pending code, and if you have a pending code, the engine light is no gonna come on, I suggest you to drive the car and when you start having problems, force it, step on gas and drive it, you might creat a hard code and you will have a better clue to start from. but check gas, it might be contamination. coils and plugs? nop, that will give you a misfiring code, injectors? the same. good luck, oh and another thing, if you do have a misfiring code, you might need to check the ignition coil, your car have a tsb on that