I took the monte on its first long road trip since I've bought it on Saturday. It was roughly 350 miles round trip. It drove great, was very comfortable and got close to 30 mpg, but I did notice a slight misfire under light acceleration while going up a hill. The MIL never came on and I never felt it any other time other then going up hills. I suspect its a secondary mis and I did plugs last week so I'm sure plug wires are to blame, but before spending $50 on them I wanted to make sure I was headed in the right direction. What do you think, plug wires, or something else? Thank you for any help

 

only uphills?

I would probably start by looking for anything that could be related to the angle of the hill. oil on the ign system or wire grounding. you seem sure its not fuel so i would have guessed fuel on a uphill power issue.

Just to help your diag i would park it on a incline and rev it and see if you can find a place to duplicate it not moving. that will help you alot in finding the issue. steep driveway or something.

 

are we positive it's a misfire?

 

I had that happen before & it stopped when I replaced the Fuel filter. I originally
thought it was plugs or wires...

 

Thank you for the suggestions. Here's an up date. The only way I can get it to do it is going down the road. I tried power braking and various other tricks and couldn't repeat it while not moving. I took if for a ride with the tech 2 hooked up. I looked at misfire data and didn't show any misses while it was acting up
Then I decided to do a few 0-60 runs to see if I saw anything then, and it had a dead miss that wasn't there before, on cylinder 6 at WOT. I was going to swap #6 with #4 and see if the miss moved to #4, but I noticed #6 was loose so I pushed it back on the the WOT miss disappeared. When I did the plugs I must not have fully seated the wire
While the WOT miss was fixed, it still has the slight one going up hills at highway speeds, and I noticed it occasionally at highway speeds under light acceleration on flat ground. While its happening it doesn't show any misses and LT and ST fuel trims look normal (between +/- 3), and the RPMs don't change so its not a torque convertor or other trannie problem. Coils and ICM are clean and oil and water free. I am going to replace the fuel filter because it looks like its never been done before and go from there. I still think its a misfire but I'm not sure from what. I'll give you an update after I change it. And thank you again for the help so far

 

if your tech II isnt showing a misfire, it's not a misfire, at least in the normal definition.

 

has your car had a good custom tune after all those mods?

 

No custom tune yet. I didn't think it would need one until I did more things, like rockers or a pully. What does a custom tune usually run?

 

Depends on the route you take. I have a guy who tunes our engines doing it for $75.

Just saying, it sounds like something maybe a tune could fix. You aren't actually pulling a code, or pulling a misfire, but it's acting funny. Maybe with an increase in tranny pressure, different shifts, timing altered etc. it could go away. But you are correct, do the rockers and all the supporting mods for a 3.4 pulley, get it tuned and you'll be happy with that.

 

moisture in the air can couse a miss fire. alot of things can. did you hook up a scan to it to see? mine has 75'000 mls, pluged in the code test, showed 2 misses from cyclender #4. could be any thing!! or nothin at all!