So the background of my car is that it's a 2003 STR with about 62,000 miles on it. Last Saturday, I started my car, let it warm up as usual as I'm in the great state of Minnesota... started driving and the RMPs started "jumping". It wasn't much of a jump but still noticeable as I could both hear and feel it. To give everyone a better idea it was a steady/constant jump of about 100 RPMs. I ended up pulling over, shut the car off, and when I started it back up it was running normal again.

So I thought, that was the last of it, then it happened just a couple days after on Monday. My drive was short that day so I just finished the drive, when I drove home, everything was fine again. It hasn't happened since but if something is wrong I certainly want to get it fixed ASAP.

Any feedback or suggestions would greatly be appreciated. Thanks in advance.

 

Was the fuel filter replaced? Top of airfliter cover secured properly to lower portion? Check for vaccume line leaks. Oil around the spark plug wells. Though you don't mention a check engine light (CEL), check for codes. A worn torque converter (TC) can cause rpm to occilate. My 03 STR recently had the trans. rebuilt and TC replaced...same symptoms.

 

Most people will probably tell you its the torque converter and some have replaced it with good results. Does it do it when driving at a steady pace and go away once the car is fully warmed up? Another option may be to have the transmission software updated. There is a TSB for similar symptoms.

 

Worth seeing when it does (& does not) do it. What RPMs, speed, etc. Post back in a while so people can better help.

 

+1, and whether it goes away once the transmission is fully warmed up. 100 RPM fluctuation is not much- I hope you don't mean 1000.

Also- there's no need or benefit in letting a car sit and warm up in cold weather.

 

Here is the Jaguar TSB on the torque converter. I can't find it in the sticky section?? I have attached another TSB concerning surging but it's at a much higher temperature?

Maybe it will help. Your description has to match what Jaguar called it.
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First of all thank you everyone for all of the feedback, I really appreciate it!

Otherwise, nothing was recently replaced (aside from the winter tires, which should have no impact) or no CEL either. The speeds which it was happening at had a wide variance. The first time, I started on side roads and then got onto the freeway, where the "jumping" was continuous from ~10 MPH all the way to ~60 MPH until I actually pulled over and turned the car off.

The car was semi-warmed up each time as well but there have been other times I have drove when it was semi-warmed as well with no problems.

As far as the specific RPMs, the most recent time when I was driving down some side roads, it was fluctuating from 1250 to 1350. I did take a video of the RPMs jumping as well if I can figure out how to upload it from my phone I'll certainly do so.

Otherwise, I'll be sure to check some of the other things today such as the air filter cover, oil around the spark plugs, and also see if anything else looks out of the ordinary.

If there is no small fix, it sounds like it may be the torque converter. Is that something typically covered by a warranty, something that's an easy fix and can be done without bringing it to the shop? I'll be sure to check out the links some of you have uploaded as well as I may be able to answer my own questions as well.

Thanks again for all of the help thus far again, I'll be sure to keep everyone updated.

 

My 03 STR had similar presentation that was cured with rebuilt torque converter covered under warranty.

 

As far as proving that there is a problem, do I just have to get lucky and hope the car is acting up when I bring it to the dealership, or is there a code that it should be throwing out? Any feedback would be helpful.

 

A Jag dealer will test drive the car then make an educated guess based on trans. line pressures.