6 Misfire Diagnostic Codes

[Russ450]

Last week the car began running rough and the check engine/TRAC lights came on. The same thing had happened in February and at that time I took it to a shop where they diagnosed/replaced a bad coil on #4 cyl ($250.00). This time, since I did not have a diagnostic tool, so I checked the coils the old fashioned way by disconnecting them while the engine was running to see if it made a change. On 2 of the cylinders there was no change, so even though I thought it unlikely 2 would be bad at the same time, I replaced them and the car ran fine for 2 days. Today the lights came on again and the car stumbled during acceleration. I borrowed a diagnostic tool and it reads 6 codes... 5 for faulty ignition on specific cylinders and 1 for general random misfire. Any ideas what could cause this? I don't think it's a bad batch of gas, but who knows? Thanks...

[George_Jetson]

Multiple random misfires can be caused by excessly lean mixture, commonly caused by vac leaks. So a good place to start is checking all hoses for splits, crackes, and other leaks. Low fuel pressure can also cause a lean condition, but you need a fuel gauge and correct fittings to check this.

I would be surprised if it was bad gas, but when was the last time that you replaced the fuel filter? While you are at it, I would buy a tank of good gas, ie Cheveron, Texaco, or one of the other name brands, and toss in a can of fuel injection cleaner.

PS. I would recomend not disconnecting components while the engine is running. Some componets will generate a voltage spike when unpluged or plugged in. It is possible to cause additional damage while you are troubleshooting.

[Russ450]

Multiple random misfires can be caused by excessly lean mixture, commonly caused by vac leaks. So a good place to start is checking all hoses for splits, crackes, and other leaks. Low fuel pressure can also cause a lean condition, but you need a fuel gauge and correct fittings to check this.

I would be surprised if it was bad gas, but when was the last time that you replaced the fuel filter? While you are at it, I would buy a tank of good gas, ie Cheveron, Texaco, or one of the other name brands, and toss in a can of fuel injection cleaner.

PS. I would recomend not disconnecting components while the engine is running. Some componets will generate a voltage spike when unpluged or plugged in. It is possible to cause additional damage while you are troubleshooting.

Thanks, I'll check the hoses. I've never replaced the fuel filter, so I'll do that too.

[vetmx1]

What are the specific codes being generated? What does the forum say about those? Have you reset the ecu by disconnecting the battery for a while? that may clear the codes.

I have a 2000 es300 w/141k. I have replaced 4 coil packs. I diagnose the same way - by disconnecting one at a time. I've replaced 4 of them. i did one a long time back, then in a period of one month, i lost 3 packs with 10-14 days in between each. I'm now carrying a spare.

my point being- i had multiples go out. maybe you too...?

My local dealer gave me a good price - $80 a coil pack out the door. retail was $92 or 96 + tax (IL cook co. = 10%!)

REF: Autozone will check your codes for free.

[Lex67]

have your ecu checked i had this happen to me at the begining of the year the code read most likely are mis fires and knock sensor are bad when i took it to the dealership they replaced my ecu and checked my cylinders due to the knock sensors going bad which was good cause they saved me money.