Hello all.

I have a 1999 Mitsubishi Montero Sport XLS 4x4 with the 3.0 V6. I'm having an odd problem, which I am wondering if it's related to an exhaust and perhaps an O2 sensor issue.

When I exit the freeway after driving 25+ miles, my Montero will slip for a split second when shifting into second gear and third gear. Once you've been off the expressway for a little bit, it shifts fine. It seems like this only happens when you've driven it at 70mph+ for 25+ miles.

Now, I do have an pretty aggressive exhaust leak at the moment between the upstream O2 sensor and the catalytic converter. Also, I am quite sure the exhaust, O2 sensors and catalytic converter are original from 1999.

I do plan on having the exhaust replaced within the next two weeks, but I was wondering if these two issues could be related? Should I mention the slip to my mechanic, or wait until the exhaust is replaced with new O2 sensors?

 

How old is your transmission fluid? It can be that it is old and is failing. This would be more noticeable after driving hard when transmission fluid gets hot.

 

Transmission was just serviced a few months back. Fluid and filter change. I believe it was in February.