I took my Bonneville fully loaded with passengers and cargo across country to northern New England. The terrain is very hilly up here in Vermont, and I find the transmission trying to hold a high gear far too long. I have to give it a lot of throttle for it to downshift, otherwise it will happily try to lug up a hill at 1200-1800 rpm in 3rd or 4th with the torque converter locked up.

When the boost gauge gets to about 1/3 of the way past 0 under 2000rpm, the engine starts to stumble, and the RPM's will fluctuate up and down as if the transmission were trying to shift out of gear. Sometimes it gets pretty violent, but it won't downshift unless I really jab the throttle, and then it's too much. I find myself downshifting myself into 3rd of 2nd in anticipation of steep hills, and I believe I shouldn't have to do this in an automatic.

I did a full tune-up including plugs and wires about 20k ago. I used the NGK plugs and Belden wires that are recommended on here.

Any ideas what's causing this and what I can do about it? I have a trans-go shift kit installed in the tranny, and had the pan drained and refilled with Dexron VI about 5k ago. Because of the way the RPM's fluctuate when this problem is occurring, I'm not certain whether this is a transmission problem, or misfire. There are no codes set, and the SES light isn't on or flashing.

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Inferno Red 2009 Dodge Caliber SRT-4 125k

I'd look at the plugs. I have to replace my plugs once a year on my 03, as it always starts misfiring in April. It's really weird. Something about going from winter blend back to summer blend gas or something. That would be my first guess.

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RIP sandrock

Check out this article and see if it sounds like your problem.
http://www.tripleedgeperformance.com/TCC_rpm_oscillation.html

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Actually that describes it pretty much to a T, except mine does it in both third and fourth gear when the torque converter is locked up. It's as if the lockup clutch keeps disengaging and reengaging under a heavy load, when boost is building at a low RPM. In third, it can jump up and down 1,000 RPM or so, making for a very unpleasant ride up hills.

I wish the transmission would downshift sooner and it'd never be an issue-- I've never seen a car try to pull itself up hills under 2k RPM like this one does. So far no other weird issues, and now that I'm back in flat Illinois, I'd have to try real hard to recreate it.

I'll probably just replace spark plugs and hope it doesn't get worse.

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Inferno Red 2009 Dodge Caliber SRT-4 125k

Strangely, it was the plugs. I only replaced the front three since I was running out of time.

Problem fixed. I can't get the stumbling or RPM oscillations to come back no matter what I do. I'll replace the rear three plugs this weekend for good measure.

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Inferno Red 2009 Dodge Caliber SRT-4 125k

Bad plugs can do very weird things.

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Bye Bye:

RIP sandrock