Vigilante

My truck has had a misfire for a little while now. The miss seems to be pretty constant, and does not seem to be affected by the temperature. The truck has thrown the p0303 (misfire #3 cylinder) code a couple of times, so i think I at least have a specific place to look for the problem. I have read a few posts on here about testing the resistance of the plug wires, the coil packs and the fuel injectors. I'm a real novice when it comes to using a multimeter, so bear with me.

To test a plug wire, I would need to insert the positive and negative test leads into either end of the plug wire and it will give me the resistance (assuming that I have the multimeter on the correct resistance setting)? I know that the problem is not a plug wire in my situation, since the #3 cylinder does not actually have a plug wire. I just want to know for future reference. Now, to test the fuel injector, I would just have to take the connector off of the injector, then touch the test leads to the two prongs sticking out that fit into the connector? How would one test the resistance of the coil pack?

Any input would be appreciated. Thanks.

netwt12

more than likely your problem is a coil. hopefully just a plug. i wouldn't even wory about the injector until i had verified it wasn't a bad coil or plug.

thmpr

The engine should be cooled down first before checking for resistance on the injectors. With a cool engine, the injectors should read around 14-18 ohms. Anything higher than that means it is faulty. I just went through an entire injector replacement which took a day to complete.




Good luck.

Vigilante

Well, I pulled the coil of of the #3 cylinder. I still don't know how to use the multimeter to test it, so I didn't. It did look pretty good though. I pulled the #3 plug as well, and it looks like it's in decent shape. I then pulled the connector off of the #3 injector and tested the resistance (I think that I did it correctly) and I got a reading of 21 ohms. I then tested the #1 fuel injector and got 15 ohms, which would lead me to believe that I am testing the injectors correctly. The engine was cold by the way. Would 21 ohms of resistance cause the injector to malfunction? Does this seem like it may be the cause of my misfire?

thmpr

its out of spec.

Texas_Ace

Sounds like you found your problem, though while you are doing all of that i would get new wires and plugs all around, for the few bucks it is well worth it to rule all of that out. Injectors get real $$$. But that does sound like your problem.

Vigilante

Alright, I'll buy a new injector and see what happens then. Thanks guys.

toy_tek

You could also swap the coil pack to another cylinder and see if the problem stays in 3 or follows to the new cylinder. If the problem stays in the same cylinder, then you could swap the injector to another cylinder and see if it follows then. I know its tight in there so I'm not sure how much time that would take, but it wouldn't cost anything.

Vigilante

I could I suppose, but the only problem with that is that the truck has only thrown that code 2 times in the past month. It may be a while before the check engine light comes on again. If the MIL was coming on more often I would definitely try your trick.