P0432 -- and stuck exhaust valve

[Heavyopp]

Ok got a problem -- 2000 cherokee -- 4.0 with cali emissions has the 2 pre cats

Replacement motor -- 27000 miles on motor -- New walker pre cats -- new NTK o2sensors -- 600 miles on both pre cats and o2 sensors

I keep getting code p0432 -- Clear it and it comes back

Now I had a problem with the previous motor -- didn't know the #2 cylinder exhaust valve was stuck open -- Had installed the new pre cat manifold and the O2 sensors on the bad head -- Had what I imagine was raw fuel dumping into the exhaust due to the stuck valve -- caused exhaust pipe after cat to glow orange at night

In searching for a replacement head I stumbled upon an entire engine with 27000 miles for $350 -- swapped that in using the newly replaced pre cat,O2 sensor combination

My question is -- If I had raw fuel dumping into exhaust - What did it damage?

I never drove the XJ but I did run it above idle while trying to diagnose the stuck valve -- Finally a compression check found it


That pre cat pipe is expensive, I hope I didn't cook one of the cats -- chances I cooked an O2 sensor? Is there any way to test each O2 sensor for damage?

Hope this make sense -- thanks for any help

Jer

 

[trippled]

More than likely it nuked the cat. I've also seen a lot of aftermarket cats still cause efficiency codes.best way to check would be monitor rear o2s when driving and see if one is toggling like a front one would, which would indicate a bad cat.

 

[Heavyopp]

This may or may not be relevant but I get terrible gas mileage too

I'm lucky to see 12 MPG per tank with a mix of local/highway driving

 

[md21722]

You could check for exhaust back pressure which would further point to a bad catalytic converter.

 

[four_shot]

More than likely it nuked the cat. I've also seen a lot of aftermarket cats still cause efficiency codes.best way to check would be monitor rear o2s when driving and see if one is toggling like a front one would, which would indicate a bad cat.

^what he said.

As an addition. The sensors can also melt down as well. Rule of thumb: If the cat is hot enough to glow, the sensors are too.

 

[Heavyopp]

so I had a friend put the good snap on scanner on the jeep -- we get a lost/ intermittent signal with the downstream bank 2 oxygen sensor -- it was too cold to crawl under there to check the wiring but at least I have a place to start

When I dumped raw fuel into the exhaust it was from cylinder 2 which would be bank 1 so hopefully the cat survived and didn't melt down

 

[four_shot]

I'm leaning towards an 80% chance of survival. It really depends on how long the cat was run like that.

 

[Heavyopp]

It was never driven with stuck valve -- maybe total idle time of 2 hours while playing around before I compression tested it

This 2 hours run time was spread out over a few weeks

I'm thinking the precats are fine and I have a bad sensor, bad wiring, loose connection

It's too stinking cold to mess with it now -- runs and drives fine -- code hasn't returned yet