Flat running at 4K

Hi guys, any help would be much appreciated. I have a 97 550. I had a slow down light going on everytime I drove the car. I replaced the Thermocouple ECU's and have fixed the slow down light problem. However, the car still is not running correctly. I hammer the throttle at 4k rpms and the car revs but very slow and without much power.

I was having this problem before I replaced the ECU's. I thought the replaced ECU's would fix the problem. Any ideas what else could be causing this. I have no CEL, slow down or any other lights going on.

Thanks in advance for the help.

Regards

 

Maybe your catalytic coverter is plugged up. You probably got the slow down light because the cat was heating up. Now it's possibly plugged up.
Just my thought.
Jim

 

How do I know if I have a plugged cat. And how would I unplug it.
thanks

 

Remove one of the fuel filters and drain it out backwards. Inspect the fuel that comes out. Just had a 550 in this spring that had all of the rubber components in the fuel tanks decomposed and plugged the filters. Look for a "fuel injection cleaners" post from a few months ago. I posted pictures of the results, and the symthoms were identical.
Dave

 

The only way to unblock a plugged catalytic converter is to hollow it out, but that's not really legal. To checked a plugged cat, you could check the difference in exhaust flow between both sides at 4-5k rpm. I'm not sure how that exhaust is set up. You may want to check the fuel filters first like Dave said.

 

thanks guys. I will try tonight.
Regards,