Travelling misfires

[Uncle Buck]

I read an interesting thread on the DOB forum and thought I'd share it.

One of the members was having a heck of a time debugging his 08 GT. Would run great for a while then through misfire codes, fall on its face and then self correct and run fine. The misfire codes were moving from one cylinder to the next and there was almost no consistency except codes tended to show up mostly on deceleration. He tried all kinds of remedies. Plugs, coil packs, an alternator, tune, retune all kinds of data logging including a couple of sessions hooked up to a Ford dealer diagnostic computer. According to all the logs, the car ran like a champ, but it didn't.

Poor guy was at his wits end trying to chase this misfire.

In the end it turns out it's related to the balancer. He had taken it off and reinstalled without using a new bolt and without following a specific torquing technique that includes rotation and multi steps to spec torque. Must have not been seated perfectly causing the crank position sensor to get confused under just the right condition. A new bolt and proper tightening sequence has resolved his problem after 2 months of chasing it.

Thought some good tech might brighten your day.

[Slope]

I read an interesting thread on the DOB forum and thought I'd share it.

One of the members was having a heck of a time debugging his 08 GT. Would run great for a while then through misfire codes, fall on its face and then self correct and run fine. The misfire codes were moving from one cylinder to the next and there was almost no consistency except codes tended to show up mostly on deceleration. He tried all kinds of remedies. Plugs, coil packs, an alternator, tune, retune all kinds of data logging including a couple of sessions hooked up to a Ford dealer diagnostic computer. According to all the logs, the car ran like a champ, but it didn't.

Poor guy was at his wits end trying to chase this misfire.

In the end it turns out it's related to the balancer. He had taken it off and reinstalled without using a new bolt and without following a specific torquing technique that includes rotation and multi steps to spec torque. Must have not been seated perfectly causing the crank position sensor to get confused under just the right condition. A new bolt and proper tightening sequence has resolved his problem after 2 months of chasing it.

Thought some good tech might brighten your day.

Makes sense. I could see that one making you want to get The Sledge out.

Always check the last thing you f*cked with.

[ZR]

Any mechanic or enthusiast worth their wt in salt always goes back to the last mod.
Cool he found it.

[Uncle Buck]

Agreed. In this case messing with the pulley was part of a blower install so I guess it added to the mystery. As soon as he mentioned pulley his mechanic nailed it.

[ZR]

While proper sequence is preferred, they end up just fine so long as your tight enough. Sounds like it was loose from the get go. I'll take an old skool torque the bitch to spec over this torque to yield nonsense any day.

[ZR]

Was he not getting an intermittent crank sensor code?

[Uncle Buck]

^^ according to his write up he just got misfire codes and the condition was very short lived. He'd drive an hour fine then 5 seconds rough through a CEL and then fine again. I guess the clue that no one picked up on was the code kept pointing to different cylinders. I found it an interesting mystery. He's the only DOB car in Canada that I know of so have been following his threads a bit. Car ran great for 6 months after the install and then started acting up. I'm just glad it didn't turn out to be DOB related.

[ZR]

That makes it a bunch trickier, key seems to have been his finding someone that actually looks n figures out a problem vs a parts replacer.