2002 Mazda Tribute/Ford Escape V6. On city streets the car drove normally, but I noticed on the freeway that it would not have power like if I wanted to pass a truck. This was especially apparent when the freeway was slightly uphill. It would cause the RPMs to go way up to 5K or so, but not enough power to propel the car faster. The transmission would shift strangely too and seemed like it was slipping in the higher gears or refusing to shift.

I suspected a bad CD4E transmission, since this is a commonly problematic transmission. I drained and refilled with Mercon V fluid, but that didn't change anything. Then I had two different tranny shops give free evaluations and they both thought the transmission was OK, so it must be something else. I finally figured this out and fixed it. I removed the rearmost catalytic converter (#3 cat) This is the one under the car, not one of the two cats in the engine bay that are part of the exhaust manifolds. Guess what? It was almost entirely plugged up. If you shine a light through the rear pipe, the front catalyst mesh media would only allow just a few little specs of light through. I soaked the cat for many hours in detergent water, but that did nothing. I then soaked the cat overnight in lacquer thinner and that also did nothing. Time for a new cat. Got a Walker cat for $95 on Amazon and some new flange gaskets. This solved the problem and now there is power on the freeway and the transmission behaves normally. I also checked the two cats in the engine bay and they were not plugged up.

So, the lesson here is that a transmission issue can actually be a catalytic converter that needs to be replaced.

 

Although the front cats are not plugged up, they may be breaking up and hence plugging up the rear cat. Might be worth checking COPs and plugs, wouldn't want to plug the new cat up too quickly...

 

That's a good point, and in this case the plugs are new and I'm assuming the COPs are fine since I'm not getting any misfire codes. On my visual inspection of the mesh media in the two cats in the engine bay, they do not appear to be disintegrating, so I think they are in good condition. Will watch out for that in the future, though, thanks!

 

 

Interesting........The car now drives fine up a slight incline, unlike before the cat change. It wasn't really missing or hesitating, though. It was just a lack of propelling power and it also had bad transmission behavior. All works fine now, but is there a reason to be concerned about the COPs if I'm not having any symptoms other than perhaps low MPG? I haven't driven the car long enough to know if the MPG is still low. I was assuming that was because the cat was plugged.

 

 

Good to know, thanks. The two cats in the engine bay are intact. If I don't have any misfire codes, is there a way to test the COPs? I'll also look up online to see any info showing how to test those. We're bringing the car back to her today (she lives 2 to 2 1/2 hours away) so I'll have to do the work on her car in a few weeks.

I appreciate your responses!