skerv

My exhaust guy and I discovered a very interesting thing today, one which he has never encounter in all his automotive years. I had my second cats and resonator removed and replaced with a magnaflow x-pipe last week. And for a while I had been hearing a constant and terrible sounding rattle, which we were sure could be attributed to the primary cats. So fast forward to today when we cut the primaries to replace them and he discovered that they are 100% empty. Essentially straight pipes off the headers and into the x-pipe then muffler. The weirdest part is that I've never had the check engine light come on despite running no cats?? I've owned the car for about 5 months now. Does anybody have any insight into how this situation may have occurred?? All that aside...he says it's now the perfect vehicle because for emission purposes I "have cats" and no check engine light and will pass just fine yet I really have straight pipes 👍👍

skerv

It is a 1999 E55 btw

snooozie

Previous owner might have a tune to delete the check engine light?

skerv

That's what we were thinking, or the downstream O2 sensors are disabled? Also, I just drove the car home and the really obnoxious rattle that was present 2 days ago is now completely gone!! Maybe the cats came apart and a piece was hung up somewhere and the res/2nd cat delete let the shard dislodge itself and make its way out the tailpipe? We were just perplexed at how I essentially was running straight pipes but never got a check engine light and wasn't told about any tunes when I bought it from a big car enthusiast. If all is as it appears now though it seems like a great situation...No more rattle, should pass emissions fine, and for performance purposes I am running straight pipes....but my computer doesn't know that

skerv

And I know the check engine light works because it came on nice and bright when my MAF went out about a month or so ago.

smaltze

I have all catalytic converters emptied on my w210, but mine is a 2002, it has no oxygen sensor at all so you have no problems. im not sure if the 1999 has one but this could be the reason.

skerv

Is your car a W210 E55? Because my 99 E55 certainly has O2 sensors...four of them to be exact (two upstream of cats and two downstream). Did you take your O2 sesnors out or was the car always like that? I pondered if somebody had maybe disable the downstream ones for cat-less travel on my car.

smaltze

no, an 02 e320. definitely no o2 sensors, perhaps its just preface lift w210s that have them..

IanB

Anything OBD2 will have post-cat O2 sensors to monitor cat health/operation, and anything fuel injected will have pre-cat O2 sensors to monitor the A/F ratio and make adjustments accordingly.


I'd be shocked if your '02 E320 actually had no O2 sensors.

skerv

This is more along the lines of what I had thought to be true. Which only makes me wonder why my downstream O2 sensors never sent a code when running totally cat-free? The only explanations I can think of is that those downstream sensors have been disabled, the ECU tuned, or somehow it's still reading within the sensors' "acceptable level". And I'm skeptical that the ECU was re-flashed/ sensors disabled because I am pretty certain the cats broke themselves apart inside and the fragments went out the tailpipe. The car runs great this way though. Nice mean growl of the V8!! Still concerned about this mystery biting me in the A** later though....