Strange Misfire after HG job, misfires only when revved

[brandnew161]

I just finished my two day ordeal of replacing the head gasket and retiming the motor. When i started up the car it ran ok when it was idling (14-16 hg due to the cams). However here's the problem. I can rev it up...but as soon as the rev peaks and it starts to decel, the motor has a hard time idling and it sounds like it is misfiring. Eventually, it finds the correct idle position and goes back to normal.

Before I replaced the head gasket I got a code for misfire cyl 2, no suprise, there was coolant in cyl 2 & 3. I checked the head for flatness and also for cracks, there were none. Also, when the car is idling, I cannot smel any burning coolant nor do I see white smoke like I did before the HG job was done. The timing was set correctly, I think this was my fourth time doing it, i even triple checked it. What do you think could be causing this issue?

Thanks in advance

 

[KKneipper]

Did you replace your spark plugs and wires when you did the HG? The coolant in your cylinders could have messed up one of them. Also, make sure your wires are hooked up to the correct cylinders. I know that most of the time the car sounds like shit and won't idle right even with one cylinder misfiring, but other times you may not notice anything until you let off of the gas. (Gotta love DSM's).

It may even be something as simple as bad gas. I would dump some octane booster in and see if that fixes the problem.

 

[brandnew161]

I did replace the spark plugs but i did not replace the wires. I take it i should replace those too?

I was able to drive it to the gas station and put in half a tank of new gas so thats ruled out now .

Finally a code popped up, misfire on cyl 1.

 

[KKneipper]

Swap your plugs around to different cylinders, disconnect the battery to reset the code, and run it until the CEL comes back on, to see if the misfire changes cylinders. If it comes up with cylinder 1 misfire again, then I would start by replacing the wires. It could also be a bad coil, but wires are cheaper so I'd start there. I had the exact same problem (mine was caused by adding more boost than the wires could handle).

I wound up buying some Bosch 7mm Mag Core wires from AutoZone for 50 bucks. I put them on in the parking lot and noticed the difference right away. They've been running great ever since. I was going to get some NGK wires, but they would have been special order and I needed my car to get me to work. Took my chances with Bosch and I'm not disappointed.

 

[brandnew161]

Swap your plugs around to different cylinders, disconnect the battery to reset the code, and run it until the CEL comes back on, to see if the misfire changes cylinders. If it comes up with cylinder 1 misfire again, then I would start by replacing the wires. It could also be a bad coil, but wires are cheaper so I'd start there. I had the exact same problem (mine was caused by adding more boost than the wires could handle).

I wound up buying some Bosch 7mm Mag Core wires from AutoZone for 50 bucks. I put them on in the parking lot and noticed the difference right away. They've been running great ever since. I was going to get some NGK wires, but they would have been special order and I needed my car to get me to work. Took my chances with Bosch and I'm not disappointed.

thanks for the help. I just picked up a set of those wires from autozone this morning and unfortunately the problem is still occuring. I'm thinking the only other thing would be the coil....but its just strange how it would go while doing a headgasket job.