Hey guys, come seeking some advice. I recently bought a 2000 Honda Accord EX with V6. CEL was on when I bought it but the car ran fine and still does. I pulled the codes and found several cylinders showed misfire, plus a random misfire code. The car had 81,000 miles on it when bought so I figured it just needed some plugs. Bought some Double Platinum plugs from AZ checked gap and installed, cleared code, but after a day or two the light came back. Next I started unplugging coil packs while car was idling, found one that made no change in idle so I replaced it. Light keeps returning! To me the car runs very well and I do not fill a misfire at all. I cleaned EGR valve and plan to clean passages as soon as new gaskets come in. Any advice on where to go from here would be greatly appreciated.

 

Check again for codes. Replacing spark plugs may have set a new code.

Listen at exhaust pipe for missing (put, put,...)

good luck

 

Thanks TexasHonda, either I'm real deaf or there isn't any put put. Forgot to mention that I have run 2 bottles of injection cleaner with last two fill ups. Probably will Seafoam next. I have ScanXE professional along with OBDWiz on laptop, so I am able to pull most data and clear codes. I work nights and a lot of OT lately, so I haven't been able to put a lot of time into diagnosis. I bought compression tester and plan on checking that also. Will post my results ASAP. Keep the ideas coming guys, just a shade tree mechanic from Louisiana.

 

Got my brother in law to listen to exhaust and said was a small put put. So I am deaf! Think that could be from 25 years marriage. Lmao!!!

 

Random misfire (P0300) usually means a fuel or air problem, and not spark.

What does Long Term Fuel Trim (LTFT) and Short Term Fuel Trim (STFT show on your scanner.

good luck

 

You can get a (P0300) with a bad coil pack

 

Hey friends, I over slept today but was able to get some things checked. Battery checked out with load tester... GOOD. Pulled all plugs and removed fuel pump/ign fuse for compression check. Did a dry and wet test...here are the results.

Cylinder #1 dry=142 wet=160
Cylinder #2 dry=136 wet=145
Cylinder #3 dry=137 wet=152
Cylinder #4 dry=130 wet=150
Cylinder #5 dry=123 wet=132 (ouch!!!)
Cylinder #6 dry=145 wet=160

Was without help and could not find a spark tester for recessed plugs anywhere local. So plan on checking that tomorrow the old fashion way. I did a seafoam application, letting it sit for now.

As for as info from scan, I will post what you asked tomorrow. Not real familiar with software because just got it, but will do my best.

 

Hey again, got the numbers you asked for.

STFT= min/-5.47
mean/ 1.47
max/ 15.62

LTFT was 0's across the board.

Hope this helps. Seafoam did seem to make the put,put go away. Waiting for your suggestions.

 

These fuel trims are good and indicate fuel distribution/injection is not causing misfires.

Any other codes besides P0300?

One low compression would not cause random misfire. It's slightly below the minimum service limit of 135 psi. Worth checking to see if leakage is valves or rings (put about tablespoon of oil in cylinder and see if compresion increases, yes rings, no valves).

Tight valves can cause compression loss and missing. This has been reported on other Honda/Acura V6's. Fix is to adjust valves.

Suggest checking for intake air leaks w/ throttle body cleaner sprayed at jts and leak possibilities.

good luck

 

Thanks again TexasHonda!! Bare with me, if you can.

I am getting multiple cylinders showing misfire. Can't recall exactly which ones. Seems like it was 1,3,4,5,6. Will double check in the morning. The compression test was done with oil added to cylinders after a dry check. #5 only came up 9 psi after adding oil. Will check for vacuum leaks in the morning also.
After seafoam treatment, getting a slight grinding sound from around the belt/pulley area. Is it possible seafoam could have damaged smog pump?
Anyway. .. cleared codes drove to work, 45 miles. After a couples hours cranked car and light returned.
Correct me if I'm wrong, but read somewhere that my car has hydraulic valves and can't be adjusted.