Driving with bad catalytic converter

[ctpres]

Originally Posted by JonBrazel

I would strongly recommend Alliance, they are good people and also work with us. If you recommend to your service adviser to bring us in the loop to help diagnose we would be more than happy to assist.

We are at Alliance. Service Advisor Mike Wittman. Five minutes explaining and first comment - probably can't fix if not showing problem now. Giving him your name and number. Hope he calls.
History leading up to exhaust rattle and tail pipe color difference. Very intermittant power loss on steeper grades and gas milege 5-6 normal towing around 8. Low power problem - once evident - didn't go away until next stop and cool down. Worst case occurance, engine sounded like running on four cyl. and needed tow. Should be in service bay today. Thanks for offer to help.

[DriVer]

Originally Posted by ctpres

We are at Alliance. Service Advisor Mike Wittman.

I met Mike Whitman while I was at the dealership. Nice guy.

[ctpres]

Since I started off on wrong foot with Alliance - decided to keep the story going.
Alliance customer facilities are excellent. Waiting room very big with numerous conversation areas. Many folks here for days and friendships established while waiting. TV, excellent wifi a couple workstations for customer use. Large campground with water, elec, laundry and dump station and again excellent wifi. $20 a night if just passing thru and $10 a night if there for service.
People: Everyone seems to be focused on customer, smiles, greetings and very pleasant. If RV in for more than one day, they go out of the way to get it back to site. VERY unusual - you can go in the shop and watch.
Day one service for us. removed cat's and mufflers for inspection - bad news - no problem found. Tech noticed fluid leak at tran filter and fixed it. Coach back in space 33 for our use by five o'clock and time set for tech to pickup in AM for day two.

[ctpres]

Day two service. No problem found. Service hour meter ticking and I have to stop throwing money at it. Wty. pretty much worthless for us. Very disgusted. Alliance - end results opinion. I would go back for service on other issues.

[Topflite51]

Have to agree with Driver, I too do not like the fact that 1 outlet pipe is clean, while the other looks normal. That's not normal.


You said there is a rattle at idle, but it is not clear to me is it at idle when you first start up, or does it occur only after driving for awhile and then coming to idle at a light/sign? Or is it both?


You said you have replaced 1 O2 sensor, having never worked on a 8.1 in a MH I don't know how many there are, I do know that on lighter units they can have up to 4 O2's, how many is on your unit?

I am quite certain that once your warranty has expired, that someone will find out what is causing your drivability issues ( the rattle at idle and the power loss uphills). Have seen it all too often, sad to say.

Hope it somehow gets fixed on their dime.

[WeatherTodd]

Originally Posted by tderonne

Glad you are having it checked out.

Broken catalysts CAN destroy motors. If the ceramic substrate breaks down, it can work its way back into the cylinders. That will wreck the cylinder walls quickly. I've seen it happen on dyno durability tests. We knew it was the cat when we found the intake manifold full of dust.

um... unless there is extreme reversion I dont see that being a problem. Plus the cat is at least 6' from the exhaust port... not to mention 2' higher.

[cb1000rider]

Sorry you're having issues.
Your rig is OBD-II EFI. I'm going to assume that it hasn't set a check engine light - correct? You need to take it to someone who is a GM master mechanic - and certified with their diagnostics. Basically every GM dealer should have someone that meets this certification. If they don't "get it" they usually call for support from GM engineering.

Modern EFI diagnostics are very good and can generally tell the tech exactly what is happening.. Not necessarily they "why" - but certainly the what. Bad catalysts can typically be detected in advance of cutting pipes...

[DAN L]

Originally Posted by ctpres

OP here: More background. Two year history of unfixable power loss on steep grades. O2 sensor replaced nothing else so far. Can now see one tail pipe soot black color and other very light color, see pic's. No check engine light. Power and mpg all ok this trip so far - but all flatland driving. Still under Workhorse wty. Old man hearing and can't really pinpoint rattle, but sure seems to be coming from cat. on side with black soot. Currently in Fl and will be near Alliance Coach next week. Would drive anywhere in central FL if someone can recommend a better place.

is the connection between the exhaust manifold and exhaust pipe tight?
there is a replaceable metal o ring seal inside it. some after market o rings are the wrong size and will leak.
if it is really loose it could cause the exhaust system to rattle and if it is leaking, will cause a lean condition on that cylinder bank.

my scan gauge 2 has fuel trim readouts that would indicate this leaking condition.
gm's tech 2 diagnostic tool should detect this condition also.
there are threads dedicated to this problem that can be found using the search function.
on this forum, ''driver'' is knowledgable about this condition.

[DriVer]

Originally Posted by DAN L

on this forum, ''driver'' is knowledgable about this condition.

I have had both exhaust manifold gaskets replaced on my engine. I would hear a spitting sound at low RPM when the gases were blowing through the gasket. R&Ring the gasket, bring a welder cause most of the studs broke on mine. The replacement studs are some type of stainless steel and it's expected that those won't rust out like the OEM studs did.

You do want to resolve any type of condition like this because it will adversely affect the A/F mixture.

[Graygulf]

I had the same thing happen to my 2006 W-22. Pulling in the driveway after a two hour trip there was a loud rattle coming under the coach. It by the sound I could tell it was tail pipe related and narrowed it down to the converter. Their was no signs of damage to the bony of the converter on the outside but when I shook the pipe I could hear the guts rattle around inside. I removed it and by shinning a light down inside I could see the honeycomb material had broken up and was causing the noise. I could not afford to replace it so a three foot metal rod and some elbow grease cleaned all the material out. I did the same to the other side and have not heated any rattle again. There isn't a 02 sensor behind the "cat" and the motor doesn't know anything ever happened.

[Walter5555]

In California you have to have a smog check about every four years and thats about when I am told that my rig did not pass the smog test.
I have a 36' 1997 Dolphin M.H. on a Chevy Chasey, it run great with or without bad catalyst but believe it or not I have put 8 catalysts on my rig séance 2009 was the first time it failed the smog test.
I put an article in the New Paper and was told that because the 02 sensor were bad they caused the Cats to go bad. Figure that one out.
It will go up a 7 percent grade in low gear at 32 miles an hour at 4000 R.P.M. towing my 1995 Saturn SL-2. now I know thats no big deal but for a large M.H. with a gas engine I think it great.
Just a thought.

[ctpres]

Appreciate everyone's interest and ideas on our ongoing problem. We will be roving the NW mountains for 4-5 months starting late May or early June. Whatever the problem is - I am quite sure it will get bad enough to be discovered. Hope to have Workhorse wty extended enough to cover early part of trip due to over 90 days of "in the shop time." Have an extended service/wty policy to MAYBE cover catastrophic engine problems. Want to upgrade to diesel - but DW says no. Will keep y'all in the loop on this problem.

[BFlinn181]

Originally Posted by Terry Walter

I put an article in the New Paper and was told that because the 02 sensor were bad they caused the Cats to go bad. Figure that one out.

A bad O2 sensor sends incorrect information to the computer which then adjusts gas/air mixture that can create incomplete combustion. This rich or lean mix can cause all sorts of problems for a catalytic converter. Replacing so many converters should have been a red flag that engine wasn't performing properly.