1998 Z3 1.9L M44 Bogging/loss of power issue. Possibly limp mode? No CEL

[jimmyfloyd]

Ok, new issue just developed with the Z3. Not sure if it is related to my Catalytic converter or not. Was driving it the other day. THe CEL was on for P0420, which is the cat code. Would not rev past about 2000 rpm, and would not go over 30-33mph. I managed to limp it home and hooked up my code reader. Only code was the p0420, and no pending codes. Cheared the code, and the car drove fine.

That was yesterday, today the car drove fine for about 25 miles, 5 stops. On the way back home, I started losing power again, engine bogging, and could not do more than 30. had a little more power than before. This time though, there is no check engine light.

Couple details:
62k on the M44.
Temps stayed fine.
Cooling system done at 45k
Dinan Intake, TB, cat back, and I believe stage 3 engine software.
Cat was rattling a bit
Exhuast note seems to be more raspy and more forward, as in coming from my left instead of from the rear.

So what could cause this? Clogged cat? Dirty MAF?

[Blacklane]

That sounds like a clogged catalytic converter.

I once had a Chevy Blazer that did that: the loss of power would come and go and the downstream (post cat) oxygen sensor code would occasionally come up (could have been P0420, but I think it was P0157: Post Cat O2 Low Voltage). There was also a new rattle under the car that I could not pinpoint. I put up with it for about a week when one day I was climbing a hill with the throttle wide open but little power. Suddenly the was a loud BANG under the car and a huge cloud of black smoke in my rear view mirror, but the car just rocketed up the hill. It was a wonder to behold! I had a couple of buddies in the car, and we re-tell the story over and over.

Later it turned out that the cat had indeed broken apart inside. I had to replace the cat and the down-stream oxygen sensor.

[jimmyfloyd]

yeah, It's a clogged cat. Couple good whacks with a hammer and it's drivable at speed again. Time to start shopping for a new one.

[jimmyfloyd]

Clogged cat seems to have been the issue. After clearing it out and getting hte car to re-learn the settings, it's back to driving well again. Probably going to need to do either seafoam or intake cleaning, but the car is drivable again at a level above mobility scooter.

Still need to locate a new cat, but at least I can enjoy it until then.

Big thanks to Chris for helping me out with this.