Stumped and Frustrated....

[kswiss]

Car is an '02 P5, 72,000 miles, bone stock.

Changed in last couple days:
Coil Packs, Wires, Spark Plugs
EGR Valve
Fresh Tank of gas

Changed in Last year:
Alternator
Rebuild Transmission
New ECU (old Alternator had a defect and fried a lot of the electronics in car.)

Car start and idle find. Intermittently will have a misfire. After extended driving (30+ minutes) the misfire gets worse. Sometimes punching the gas helps, sometimes it doesn't. Problem is far more pronounced under load. At times it seems that a cylinder (or 2) completely stops firing for extended period of time. Stopping car and restarting will usually temporarily solve the issue, but for a matter of minutes at most. Stopping and letting the car rest for several minutes will usually reset the problem.

Only CEL code is P0300, random misfire.

When it is driving good, it drives very good. Once it starts having an episode, it is hell to drive.

Since I've gone through the ignition, I'm thinking of going through fuel next. I wonder about the older electrical problem possibly frying something else, but I don't see why the problem would be so intermittent if there was a fried part somewhere.

Any ideas? Thanks in advance. I've already searched and read all related threads, and there doesn't seem to be an answer for this particular situation.

[cspcrx]

Is it possible you have an injector the sticking or going bad? You can use a long screw driver or automotive stethoscope to listen to the injector to hear if its ticking. Had a similiar issue on a Honda and found that I had a bad injector and found it this way. Just something to consider.

[kswiss]

I think its possible. The only odd thing is that it is a random misfire occuring in multiple cylinders. If it was an injector going bad, wouldn't it only cause a misfire in one cylinder?

Today, I pulled the fuel pump and replaced the strainer, also cleaned the MAF sensor and added a bottle of seafoam. Test drove it and got a misfire again, but not as pronounced, didn't last as long, and was much farther between episodes. My plan is to drive like a demon for a couple days and really get some fuel moving through the system. I guess I'll see where I'm at from there.

Any other ideas are extremely welcome.

Thanks

[kswiss]

So, as mentioned in another thread, I opened up the hood while the car was acting up, and by chance saw an electrical short between the first fuel injector and the valve cover. On further inspection, it seems that the PO had done some after market work on the car, then turned it back to stock. There is some sort of hanger for the wiring harness as it goes across the top of the valve cover, and my car is missing it.

I used electrical tape and separated the wires, and then hung them from the bar that runs over the valve cover so they wouldn't ground out, and so I could see shorts better if they happened.

Took car for test drive. No CEL, no misfire. Must have been my problem. Now just need to find a source for that hanger, and probably a new wiring harness, (or at least that piece of it.)

[widgit117]

Aw snap! I hate it when people do that. They mod their cars and when they sell it they take all the parts off and forget that alot of the time you have to add or modify the existing components. Then they return it to stock not even thinking about the next driver.

[Diehonda]

Glad you got is squared away!

Check out the FS section for part outs, pm a vendor, or check a local junk yard for a regular protege, P5, or MSP.

If I am understanding you correctly, you are missing the cover that goes around the wire harness that goes across your valve cover. Youc an get a plastic spool from Autozone that has a split down the side. Tape up the wires, cover them with a section of spool, then wrapit all in electrical tape. the attachments that hold the wire in place on the valve cover are crap. The threads break easily. The wrapped spool can rest on the valve cover without issues.

[jamesk]

Check the Crank and cam sensor, make sure those are in working order.

[kswiss]

Problem still persists.... not nearly as bad as before though, so I'm figuring the wiring was contributing to the problem. It really seems like either an injector (or multiple) is cutting out, or its fuel starvation. I need to find some way to check fuel pressure continuously to see if the fuel pump is failing, if not that leaves just the injectors and wiring.