Hesitations, lower RPMs, more when cold

Over the last few days I’ve been feeling a very noticeable hesitation with light acceleration. It’s like the car is jerking or going over a bump. It happens more strongly when cold and in lower RPMs (<2500), though it does still happen when warmed up and higher RPMs albeit less often.

I’ve attached a log. Anything look funny?

Thanks.

 

Looks like a slight misfire

 

Ok thanks. I was hoping it was something like that. I’m planning to replace the spark plugs and clean up the one grounding plate (again…). Hopefully that’ll fix it.

 

It took a while to find the time but I replaced the spark plugs and cleaned up the ground plate. Issue still remains. On a side note, I was very pleased to see that the old spark plugs (15k+ miles) looked great.

I’ll try some fuel system cleaner.

 

Ok, fuel additive seems to have had no effect (tried Lucas fuel injector cleaner and Techron fuel system cleaner).

The temperature has warmed up some and the car is acting somewhat better. So the cold definitely makes it worse.

So spark and fuel are not likely issues. No CEL’s. And a definite jerking/hesitation much more pronounced when cold.

Could it be an issue with the transmission, transfer case, or rear diff? Vacuum leak?

 

Ok I spoke too soon. Seems like the Techron did the job. Hesitations/jerks suddenly disappeared and have been gone for a few days.

I’ve been driving the MS6 a lot more recently and often go below 1/4 tank. I think my fuel tank is dirty and in the past I never let it get down that low.

Now I just need to figure out the very intermittent knocking while idling. Hoping it’s just a pulley…