I have an issue with my 98 xj 4.0 in which I'll be on the highway doing 65 or so and it'll be at a normal RPM with my foot on the gas around 2800 or so. But if I let my foot off the gas, the RPM will drop to about 950-1000 and then go to about 1200. It seems very strange. Is this normal? What should I start checking if it isn't?

Thanks in advance.

 

Assuming it's an automatic? If so, normal behavior.

 

I have the same issue. And I don’t think it’s normal.. for me that issue goes away after a set the computer. And it’ll be fine for anywhere from a week to 3 weeks, then comes back.. also. My rpms will surge while coasting, at about 60 mph they jump down to 900 rpms the. Back up to 1200, and do this every 3 seconds or so. I can’t figure out what the deal is..

 

You guys ever clean your throttle bodies?

 

What if you coast in neutral?