P0300 3-5Krpm triggers Check Engine Light and Hold light flashes.

[Christopher]

P0300 3-5Krpm triggers Check Engine Light and Hold light flashes. Otherwise my wife’s 2005, 145kMiles runs great.


I have searched the forum with varied success concerning this issue. It seems like it haunts more than one owner. I have a new clue to solving the issue. Since I have tried remedies from many different threads I would start this one in hope of finding a answer once and for all.


I have found that many things can cause a P0300- Random/Multiple Cylinder Misfire Detected


Vacuum leaks, bad coil, bad wires, EGR Valve, Fuel pressure or pump, Fuel injectors, .


I have changed the plugs, wires, coil, changed the EGR valve, check the batt cables, and battery, and all vacuum lines and the problem still exists.


While the last round of testing I have found that the code starts when under load in third gear right after the shift. Not to say that easy driving also produces the code and lights.


Any further suggestions?

[avguy]

A realtime OBD data stream reader might be helpful in diagnosing your misfire. There are phone apps available as well, which cost less than a commercial reader unit. You could also remove the throttle body and clean it, along with the TPS and IAC, both of which can be removed from the TB on the '05. And yes, there are many things that can cause misfire, including others that you didn't list.

[Christopher]

Thanks I'll work on the TB next.

My meter does show live data however I don't know what I should be looking for to help with the problem.

[petrified.rabbit]

What kind of spark plugs did you use?

If you run correctly and only have a flashing hold light + CEL, the problem might not be a misfire at all, it might be the signal from the coil to the transmission ECU.. This could be a bad ground on the transmission, or it could be strictly a transmission problem. If you replaced everything else, check the coil again, make sure the replacement had the same number of pins in the plug, and even swap them back to see if the problem is the same. Trace out the wire. The hold light and the coil at the same time suggest coil is the issue.

[Christopher]

Bosh Platinum plugs but just got a set of copper core to swap out. will check trans ground and swap out the coil and check the plug.

Thanks for your input.

[Christopher]

Changed the Trans filter and fluid. Ground wire seems to be in good shape. Did not seem to cut out on my test drive but roads were miserable wet. Did notice that on top it all I found found the pass side ball joint to be bad. Which would account for that shaky wheel.

Most likely will do the struts also. Merry Christmas