have horrible mileage lately, around 12 MPG or less. took a look at the cat and saw the glowing ring around the rear O2 sensor, figured my cat is bad.

plugs are new, coils and plug wires unknown life, 63k on the engine. i have BHR kit waiting to go in, but haven't installed to avoid hassle from the dealership.

driving-wise it is fine, no stumbling, no CELs, blinking or otherwise, occasional shuddering on idle.

i bring it in to the dealership, and they say my cat is deteriorating, and the rear O2 is melted. i need a new cat for $1600, new O2, new wires and coils for $700, and compression check for $215.

i say, ok gimme my cat under warranty, i'll take care of the rest. they say they'll call me back.

they call back and suddenly my cat is actually good and can't be warrantied because it passes their minimum tests, my ECU has misfire codes, 4 misfires on each rotor within the last 10 cycles, and the raw unburnt fuel is the cause of my melted O2 and overheating cat. the cat is not deteriorating, but rather has 'a few tiny pinholes, which are not a big deal, but show that it might need replacing later on'.

i have a a carPC running Centrafuse, which is hooked up to my OBDII port (which they hassled me about too), and there are no misfire codes at all.

so my questions are 1) is it possible something is stored in the ECU that i am not seeing, and 2) are these guys just completely full of it or what?

 

1) Yes
2) No...the warranty claim was probably denied by MNAO so they had to come up with something. Replace your parts...install a high flow cat or midpipe...and save yourself the money. If you replace everything and your mpg doesn't come back up to normal put the cat back in and take it back up there.

 

"they had to come up with something" doesn't exactly jive with "no, they're not full of it".

i just find it a little suspect to say the least that they are happy to recommend a $1600 job, along along with another $1000 worth of work, and when i tell them i want it under warranty, it is suddenly functional.

it's in such horrible shape that i need to get it changed, but it's not bad to warranty?

why is it that there is thread after thread on glowing hot bad cats but not a single one with an overheated cat due to bad coils?

 

It is possible that one of your leading plugs/coils/wires are failing causing the trailing to do all the work which would be seen with decreased power and a glowing cat. It's plausible so they aren't completely full of it...just a stretch...especially based on what they had told you already.

 

btw...interested in seeing what a melted O2 sensor looks like so if you could snap some picts of that...

 

i do, and i was honestly hoping to fail... but i don't think they are very stringent. they basically hook up to the ODBII port with the ACC and check for codes, then at idle and that's it. no tail pipe hookup, no load test. it takes around 90 seconds. one would think if i were dumping raw fuel down i would fail regardless.


i'll take a look and report back, but i bet they are full of it on that too and there is just some minor damage to the harness or something. never had any CEL or O2 trouble codes.

on the plus side, i picked up the car today and told them to get stuffed for their $140 diag fee. got a free car wash out of it too