Cylinder #4 misfire!

I've triple checked the plugs and wires. Everything is nice and tight. Guess its time to take it to a shop

 

I have had this exact same CEL and the same thing happening on my '03 3.4L...I only get the code occasionally, and it only happens when it takes a few too many cranks to start the truck.

I have done everything, like you have said, swapped coils, checked plugs...although the code was gone, but, it did come back on one of those days when it took a longer crank to start.

I just gave up, it runs fine, gas mileage hasn't changed any, been doing it for over 2 yrs and maybe happens 5X a year to me.

The hell if I am going to pay a shop, or even worse the dealer to tell me something I already know.

 

phd- okay no cel you say, but I assume a code telling you misfire on #4.

Process of elimination free thinking here.

I know you have checked it, but does not hurt to check again. Check all your connections even the simple one of getting the spark plug boot/wire seated on the plug right. I had one that looked like it was on good, but then when I wiggled it and pushed down on it the wire seated and clicked onto the end of the plug.

Have you had the engine in water (i.e. power sprayed it to clean it etc). Could be an issue until it dries out maybe.

If it is ignition related and it is not a connection issue then you can test the pieces and see where you are if you have an ohm meter.

For the v6 the spark plug wires should have a MAX of 25,000 ohms resistance per wire. While testing this hold the test leads in solid and gently move the wires around a little. This will help you find any internal issues within the wire. Any that have higher resistance than 25,000 need replacing.

On the coils, remove the plugs and test the primary resistance. Connect the meter, one lead to each prong, on the coil where the plug connects. With the coil cold the reading should be .67 to 1.05 ohm. If not within this range then replace the coil. Can get you the "hot" readings if you need them as well. Just don't have them to hand at the mo. If you've not run the truck and it isn't in the middle of a below zero blizzard where you are you should be fine with the cold readings.

To test the secondary resistance on the coil you will need to remove the coil. Then test from where the coil connects to the plug to the plug wire connection. The cold resistance should be between 9.3 and 16 ohm. If not within that range replace the coil.

You could have an injector issue. As mentioned on previous posts, you could swap the injector to another spot, erase the code and see if the problem moves. Have you tried running some Chevron fuel system cleaner through it?

As a thought, how does the plug look on that cylinder? Any fouling, raw fuel smell, glazing, soot, black gunk, damage? When installing the plug are you taking care to install to 13 foot pounds torque? Are you taking care to remove the plug wire correctly and not pulling on the wire itself?

Cheers

Wrote all that and finally had a moment to find the link for the factory service manual pages on the ignition. Gives same info as above, but gives you the hot values as well etc. Hope it helps. Let us know how you get on.

 

Thought I would post an update on this. It did turn out being the cylinder 4 injector so I ordered a new one and waiting for it to get here in the mail. Thanks everyone for the help

 

Sorry to revive an old thread and maybe some haven't been on in forever. Where can I get the injectors flowed? Any particular shop?

 

In case it helps any body, I had the cylinder 4 misfire code and it ended up being my spark plugs were shot. All of the electrodes were down to little points. I am ashamed I let them get that bad.

I had the sudden shuddering and lose of power, check engine light came on, pulled over and checked P0304 cyl 4 misfire. Reset and limped home. CEL came on right away, if I gave it half throttle the CEL started flashing.
Got home and had CEL P0304, P0171 (lean Bank), P0300 (Multi Misfire), 305 (cyl 5 misfire).
New plugs and wires and it runs like a champ!
2004 TRD, 200k

 

I started with a p0300 and now I have a p0304. I've added a new fuel pump, fuel filter, had injectors cleaned and rebuilt, new coil packs, new wires, new plug in #4. I've swapped the coil packs around even though they are new and I still have a p0304 code. Compression test with cold motor was 1-160, 2-175, 3-160, 4-165, 5-175, 6-165. #4 held preasure for at least 5 mins. Thoughts on what else to check? Thinking about pulling timing belt cover and double checking TDC.