Diagnose this! (check engine light on, misfire)

Ye olde check engine light is on. Truck is a 99 2.7L w/ 4x4. Codes are P0300 Random/Multiple Cylinder Misfire Detected and P0302 Cylinder 2 Misfire Detected. I initially thought it would be an oxygen sensor because the exhaust stinks like there are emission problems.

Here's what I've done so far: a check of spark plug 2, and it was loose, so I thought that was it, but it wasn't. So then switched spark plugs between cylinders, and it didn't fix it. So then, switched wires between cylinders, didn't fix it. So, bought a new coil, and that made it misfire worse, so I'm assuming its not the coil. (got a refund on the part).

Any other suggestions? Fuel Injection? Any electrical further up the line to look out for? I'm hoping to drive this 600 miles this weekend. It runs ok, but I don't want to damage the engine, etc.

Any help appreciated.

 

What kind of plugs are you running and how long has it been since you changed them?

 

Thanks for the reply. Plugs are 3 years old, have maybe 20K on them. I think they are NGK's, but I forget. I'll check tomorrow in the daylight (it is pouring rain now too!) and let you know. If you got a suggestion on plug type I should use, I'm all ears. I might as well change the plugs to new, as that is so cheap.

 

Well my 2000 with the 2.7 did the same thing with the misfire but I had recently put platinum plugs in it from toyota. I knew there was one engine that the platinums would not work in and got reminded right quickly which one it was. I usually put Denso's in mine but this last time when I figured it out I just put NGK's in it and it ran fine.

You haven't washed the engine lately have you? Pull the plug wires and check down in there around the plugs to see if there is water shorting the plugs out. (Yup did that too.) Other than that IDK. I hope you can get it figured out. That's all I got.

 

Do you know if the plug is misfiring? have you looked at the spark with the plug out? does it look strong? Fuel delivery in that cylinder and all cylinders might be suspect. check fuel pressure.

 

Is there a distributor on that year? Cap and rotor?

 

I believe the 99's had coil packs like the 2000

 

I am sorry that you still have this problem. You may want to look at the intake for a vacuum leak. A hose or a gasket could be leaking and giving the code. You may want to look at the throttle body and see if it dirty. If it is dirty, use some intake manifold cleaner to make it run better. You could also have a EGR problem that will make the code trigger. It is a lot to do for this problem, because the P0 code is a general misfire code and not a specific one, so you have to look at many different things. Good Luck.