PeachParts Mercedes-Benz Forum - View Single Post - 97 E420 carbon build-up = $5600?

stevebfl · #12 05-01-2003, 07:15 PM

There actually could be some merit to their diagnostics, I was only trying to get the angle and Doc does bring it up. I didn't read your post close enough the first time.

The fault code that you probably have is for secondary air injection causial chain. I think those last words are some Germans loose translation. Basically what it would mean is that everything about the air injection system is working but it doesn't get the job done.

The way you test this is to go to the activations screen on the scanner. One waits till the O2 sensors are closed loop and the scanner allows one to make the airpump work while monitoring O2 sensor voltage. When this happens the O2 sensor which has been floating between .2v and .8v must go to below .040v in 60 seconds. If it works it happens immediately. If there is a restriction the effect is reduced. The results of this test must be known.

I have heard of this restriction and maybe Doc can tell us a simpler way to clear it. I have read posts about this "fix" but don't remember what the answer was but I'm pretty sure it wasn't removing the heads.

Just because I have heard this problem doesn't mean it is the answer in your case. I have fixed a number of air injection problems that were flow related that weren't in the heads. The hosing must be tight and the vacuum check valve both must be applied and work. There have been problems with corrosion in some cars in that valve and in the pumps. If I am right about their concept the problem is lack of performance in the above test.