Captain, I replaced the fuel filter and it didn't have any change. The one I took out was pretty good yet, but I figured I would swap it out anyway. The if the fuel pump is the culprit, would it be intermittent with outside temperature?

 

Possibly. Connectors and wires can expand and contract with temperature changes, humidity, etc. Or it could just be coincidence. Might even be a crappy armature in the pump motor. That's why you need to try the pump several times, looking for somethng intermittent. Can't leave any rocks unturned with an intermittent condition. Could be most anything, but at least the freeze frame data told us it's lean. That alone let out a TON of possibilities and narrowed down the search. We're not out of the woods yet though.

 

Tomorrow I will check the connectors around it, see if any are rotted etc. One thing I always noticed was that sometimes you could hear the fuel pump whining while the engine was running, and I have a pretty loud exhaust. Not sure.

I did mention too, that when I took it to a mechanic he said that it was the two middle cylinders with the misfire, (3 & 4?) and the other ones were okay. A bit odd?

Oh, I also have this catalytic converter waiting to be put in. Should I wait to bolt that sucker in? I know with all the unburned fuel from the miss, it would ruin it. But the guy also said possibly the cat will solve the issue due to restoring backpressure....And if it doesnt solve it, I would obviously be damaging a new part.

 

If you can hear the pump from inside the truck with the engnie running, something's wrong with it.

As for 3 & 4 misfires: most likely a coincidence, they are next to each other in the firing order, but an ignition misfire, (crossfire in the cap) would cause negative fuel trims.

Don't install the converter until the misfire is repaired. If you suspect a restricted converter, remove both upstream oxygen sensors and take it for short test drive. Removing the sensors will reduce backpressure caused by a restricted converter.

 

I can only hear it when im walking around it outside, not inside. I actually just have a straight pipe in place of the converter because the last guy cut it out and didnt want to pay for another one I'm sure.

 

I'd wait to install it until all performance issues are taken care of. No sense taking any chances. As for the comment about "restoring backpressure": A good converter does not affect backpressure. You'd never be able to tell the difference between the straight pipe and a good converter, other than the sound of it. If you put a pressure gauge on it before and after installing the converter, there'd be no difference in the readings.

 

that makes sense. Just by looking through the new converter, it doesnt look like it would cause much backpressure anyway....But I agree, I will wait until the issue is fixed. For now though, I'm at a loss. Faulty PCM/ECM?

 

See posts #20 & #22 again. Let me know what you find. Extremely doubtful the PCM is bad.

 

just wanting everyone to know that the issue was fixed. can you guess what it was?


Dizzy cap and rotor!! Even though I replaced it 2-3 months ago, it was fried. And that didnt solve the misfire even when it was brand spankin' new, so that explains why I overlooked the dist. cap and rotor as a potential problem. My word of advice, and I've seen it all around this site: NEVER USE CHEAP AFTERMARKET PARTS! I didn't believe it at first either and figured, hell they all have to be the same. That's not the case, and I learned my lesson.

Cap, you're the best and I can't thank you enough for all your time and help you've given.

What will the next problem be? HAHA.

 

Never fails. Most of the time going cheap does nothing but cost more. I learned real fast in my business back in the 80's that in the machining business that that cheap drill or end mill will barely cut wood much less metal. Might be fine for Harry Home owner that will burn up about 5 of them at a cost and aggravation of more than buying a decent tool to start with. But then again I can see why it is done with the economy and the cost of good stuff these days. Do I eat or buy a good tool. Hard choice.