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Garage => Mechanicals => Topic started by: secondslc on 21 September 2020, 09:30 PM

Title: What causes cats to smolder on a 6.9.
Post by: secondslc on 21 September 2020, 09:30 PM
Hi Guys,

In my next adventure, I'm playing the game of, are my cats bad, self healing, or is the transmission leaking on them.

I know I'm a ways out from getting my fueling tuned properly (a gauged cold start to full warm test is happening this weekend). But I do have a concern before I start taking the car for drives further than around the block.

-Letting the car get to operating temp is ok, but as soon as I start upping the revs and parking it in the driveway, the cats smoke like crazy (lots of white smoke). At first I thought it was 20 years of "stuff" burning up, so I pressure washed and degreased the underside of the car and it's still happening.

-I know I was dumping an extraordinary amount of fuel while I was getting it running, I have a massive amount of soot unburnt fuel on my driveway as a result once I got the thing running and was able to rev the engine (as evidenced by the picture). I am not dumping soot/fuel from the tailpipe anymore, but I wonder...are the cats still burning up a lot of fuel or are they so clogged that they're dead?

-My transmission leaks while sitting parked. More than likely its the front pump seal. But my question is, does the transmission usually leak on the cats? I dripped some ATF on a hot manifold, and it smoked white just like the smoke coming from the cats... If this is the case, then I need to not drive this car and fix the leak.

Anyone have this experience or do I just need to keep poking around the car and finding any external leaks once I get the fueling dialed in?

(https://i.imgur.com/uWpmANo.jpg)
Title: Re: What causes cats to smolder on a 6.9.
Post by: daantjie on 21 September 2020, 09:57 PM
Highly unlikely the smoke is from the transmission dripping on the exhaust but I suppose it's possible.   You would think then that you will see a lot of wetness in general around the transmission like around the pan as the lowest point, also around the mount and exhaust brace.
Best to give the whole area a good clean and then place some cardboard underneath overnight then you can pinpoint the leak location.
Title: Re: What causes cats to smolder on a 6.9.
Post by: rumb on 22 September 2020, 06:32 AM
If the engine is running decent it's time for an Italian tuneup. Go drive the snot out of it for 20 minutes.
Title: Re: What causes cats to smolder on a 6.9.
Post by: secondslc on 22 September 2020, 09:31 AM
I will lean it out slightly more (backfires in the tailpipe) and then go from there.

I fixed a passat with the italian tuneup once... but thats a much less expensive car to break!