So my brothers Dakota is having low power while under load, a misfire every 30 seconds or so and is hard to start. So if he's driving up a hill for example it loses most power. It gets an odd chug every 30 seconds or so and then a gas smell. The ECM is reporting a Cylinder 2 misfire. It also has a whirring noise on the driver side of the engine that almost sounds like a bad bearing. Its loping pretty bad as well. All of this started with the hard to start issue that was "fixed" by replacing the distributed cap. I've already checked the firing order and that was fine. The wires didn't show any immediate damage or pinches. Any idea's on how to continue to troubleshoot this?

 

What about the rest of the ignition parts?

 

Well according to him the spark plugs were changed with the distributor cap as well as the cables. Should I trust that it is cylinder 2? I've read around that the ECM often flags the wrong cylinder for misfires.

 

Unplug the wires, one by one. See which one has no effect on engine idling... that would be your problem cylinder. As far as the wheel bearing, be sure to replace both, if one is bad. You can grab the tire at opposite sides and rock hard to see if there is play, but doesn't always work.

 

Oh the wheel bearing is fine. The noise is only audible when parked/stopped. It sounds like a bearing or something vibrating against aluminum. Also it sounds as if its under the driver side valve cover or close to that area.

 

An engine that is "missing" one cylinder can sound unbalanced, which is probably the bearing sound you hear. Problem should resolve itself when the misfire is fixed.

I think the first thing I'd do is make sure all of the wires are fully seated. If you don't get that positive click, it's not fully seated. I've had them in the past where a single wire might not want to click on the cap. Danged things actually fight back occasionally. Another interesting problem I also had one time last century was the pickup coil was cracked. It required tearing the distributor down completely to replace it.

A typical test for the source of misfire is to move the plug and wire to different cylinders to see if the problem follows. For this, #2 is misfiring so you'd move the plug to #4 and the wire to #6 (move both ends, not just one) and if you get the misfire code on the cylinder you move to, you've identified the problem. It doesn't matter which ones you select, so long as you move them to different cylinders. On a multicoil engine you'd also move the coil, but on a distributor if you move everything and the problem doesn't follow the cap becomes suspect. Of course, this does depend upon the computer being accurate at detecting the correct cylinder. In addition to the pull and run test, if you have an infrared thermometer you can scan each exhaust port on the head. Under normal operation they should all be pretty close in temp, but one that's blowing raw fuel will be considerably cooler than the rest of them even if it's one of the center ports.The exhaust manifold is not hot enough to ignite fuel, but it is hot enough to evaporate it and when a liquid expands into a gas it gets cold, relatively speaking. You still won't want to put your thumb on it.

The fuel is not an issue right now, it's a symptom. The cylinder that isn't firing is putting raw fuel into the exhaust, and that is what you smell. Once the misfire is fixed, the fuel problem should go away.

If you resolve the misfire and still have a raw fuel smell, you'll need to start troubleshooting that as a separate problem. I don't know if your truck has individual fuel injectors or not, but if it does you can add a leaking fuel injector to the mix. A leaking fuel injector will leak fuel into the cylinder at the wrong time, then not have enough pressure to put the correct amount of fuel into the cylinder.