2009 Challenger 180 - struggles between 5000-5500rpm

[MolsonB]

Hi, first time poster on here.
We fixed up and rebuilt a 2009 Challenger 180 SE, but it seems to struggle between 5000-5500 rpm. Like it's misfiring. Full throttle is fine, once we get past that RPM. I'm pretty sure we put new plugs in it last year, but going to buy new ones just incase. Any ideas ?

 

[MacSeaDoo]

I had a simular issue and it was bad coil.

They are expensive so for me I bought one new coil. I noticed that one spark plug had a bit of carbon on it vs the rest so put it there first. It was the right one problem gone.

If that was not it, I would have moved it now to the next cyl and repeated.

Worst case scenario if not it, I would have a spare coil.

 

[MolsonB]

The odd thing is, if it was a bad coil or sparkplug, why would midrange struggle, yet WOT is fine? Is midrange more load on the engine while it gets on plain?

 

[MacSeaDoo]

Have no idea. I had it where it would studder and bog in midrange but if you could push through it, it would hit 8K rpm.

CYL 1 coil swapped with a new one, gone. Again I noticed slight carbon on that plug.

It is either air, fuel, or spark.

As part of my troubleshooting to get there:

1.. I pulled the SC and tested the clutch breakaway force. Was perfectly in spec.
2.. I put a fuel pressure Guage and ran it. All good.
3. I had the Candoo software and all sensors and readings were in spec.
4. I had replaced all plugs at the start of the season and actually bought and replaced with another full set as it was cheap.

Your mileage may vary.

 

[MolsonB]

Well I did a few tests on the water. Cyl #2 broke it's grounding spark plug strap. Replaced it and the struggle at 5000rpm went away. But after a few pulls, it broke it again. Once warmed up, compression tests shows 90/90/120. We will be pulling engine this summer and see what's going on inside.

 

[MacSeaDoo]

Curious to what is the grounding strap? Do you mean the ground on the 2 pin connector to the coil?

 

[MolsonB]

The ground metal tab on the end of the spark plug (Side Electrode, might be the official name)

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