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

 

[no cigar]

Got a load of Delco stuff coming this evening. Cap/Rotor/OEM Iridium plugs/Wires and a new MAF and coil.

Holding my breath that this fixes it.

 

[bigfootchiro]

Did he mean "dead" as in they have no compression?

 

[no cigar]

Tech ran a relative compression test and all was well on that test.

So today I replaced plugs, wires, cap, rotor, solenoid, and MAF. All parts OEM Delco, MAF was Delphi redesigned.

Absolutely no change in idle/drive. Engine shakes the entire truck and wants to die when shifting into reverse. When I was doing the cap/rotor, I made sure to try and wiggle the dizzy and it was nice and tight. Plugs were all gapped at .060 out of the box.


Fuel pump, filter, and redesigned Delphi spider were done in Summer 2015.

 

[DallasTahoe]

Pull the dizzy and check the gear for any wear, if it’s got significant wear or missing teeth then that may be your problem. Also even though you’re tech checked compression you may have a cracked head or blown head gasket. Sometimes they don’t show on a compression test because the engine isn’t under the constant pressure of it running, but Usually when you have two cylinders next to each other showing as misfiring that’s the case. Also check valve lash you could have a couple of collapsed valve springs. I only bring up these since you’ve replaced all the easy stuff and I’ve been there done that.


Sent from my iPhone using Tapatalk

 

[bigfootchiro]

Yep, just what @DallasTahoe said. Those were going to be my next words.

 

[no cigar]

Just an update. Won the idiot award.... #5 and #7 plug wires crossed. Replaced those two plugs with new iridium and runs like a champ. Now on to the EVAP code which I'm sure is the vapor line from the canister to the intake. It has a broken quick disconnect.

 

[bigfootchiro]

Just an update. Won the idiot award.... #5 and #7 plug wires crossed. Replaced those two plugs with new iridium and runs like a champ. Now on to the EVAP code which I'm sure is the vapor line from the canister to the intake. It has a broken quick disconnect.

HEEEEY, welcome to the Idiot Club! Where we’ve all been there, done that, and screwed the pooch at some point in our lives.

DILLY DILLY!!!