Misfire back with a vengeance.

[no cigar]

Hey guys. Had been chasing a misfire for a while. Had cleaned the MAF and disconnected the battery. Truck ran awesome for a few months before the CEL was back on. Truck got a new trans about a month ago and have been driving it with a constant CEL-random misfire.

Last night I leave the house and get into the pedal with almost no acceleration. As I'm giving it about 1/4 throttle the truck doesn't accelerate and stutters. As I'm driving there is a noticeable rough running condition under load and at idle/neutral. As the truck shifts into 3rd gear, CEL now blinks. Last time this happened, the spider had a wire rubbing on a mounting bracket and was shorting out. The engine is running so rough it's a noticeable vibration - but nothing mechanical seems to be broke. No noises coming from the engine.

I guess I'll start testing for spark and chase it to the distributor?

 

[bigfootchiro]

Have you checked what the code is this time?

 

[Scottydoggs]

check your cap and rotor, they like to crack or just wear out.

 

[no cigar]

The truck is at home this afternoon. I'll be leaving work early to get it somewhere where the code can be read.

 

[no cigar]

I should ad that within the last 2 years its had:

• New fuel pump
• New fuel filter
• New cap/rotor
• New wires (x2)
• New plugs (x2)

 

[willxfs]

You may want to check for play in the distributor. Heck, you may want to pull the distributor and check the gear on the bottom. It mates with the camshaft and is known to wear out over time. Just make sure to mark the distributor and rotor positions before you pull it. I'm chasing a subtle misfire right now (no CEL light). Have all new ignition components. It can be frustrating...

 

[Scottydoggs]

cap and rotors are a yearly change in my book, they dont last to long, they crack, get moisture under them and wear out. the last one you put on might have been bad new in the box.

 

[gin_road]

Some of the problems with distributor caps is the mounting plate the cap attaches to. Look for a small vent screen on the plate. These screens will get a coating from oxidation and stop up. This traps moisture in the cap causing crossfire as the rotor turns. Also not a bad idea to only run AC Delco parts on ignition system.

 

[no cigar]

Had mechanic friend of mine come over and run the truck on a Snap On Zeus scanner. Looking at the misfire counts, cyl 1 and 2 are dead holes right now. He'll do more testing in the morning to see what it is. Also suggested that one of my cats is bad as well. Can small unburnt fuel coming from the exhaust.

 

[scotto0609]

If your mechanic said there were 2 dead cylinders than that would account for a raw fuel smell