99 Suburban stalled and died on the highway

[misfitt006]

Ok so I've got a 99 Suburban LS 4x4 with the 5.7 and only 109k miles on it. I just got it less than 2 weeks ago from a reputable dealer in trade for my 02 silverado (needed a bigger vehicle now that my kids outgrew the backseat of the truck).

Yesterday I had to take it into the dealership for them to repair the A/C that they agreed to fix when we bought it. When I went out and started it there was a horribly bad rattle coming from the undercarriage. Told the mechanics about it when we got to the shop and we both chalked it up to a broken hanger on the exhaust pipe (sounded good at the time and the sound matched the explanation). The rattle was gone by the time we got to the shop so we couldn't duplicate it and it didn't return when we picked it back up so I put it out of my mind.

My wife took it to a business meeting today 60 miles from the house and right as she was getting into the city things went massively wrong. This is the story as she tells it.

She had the cruise control set at 55 mph and she said it kicked off right as the exhaust started blowing a huge cloud of black smoke, it started chugging and then died as she was driving. She got it pulled off the side of the road and called me. She tried to start it as I was on the phone and it would turn over but not start so I drove out to her (thankfully we have a 2nd car).

When I got there I tried to start it and it fired right up but the rattle was back and the Service engine soon light was on. I crawled underneath it to investigate the rattle and saw 2 cats on the exhaust. Laying on my back and looking up there was 1 cat close to me and another one just to the rear of the vehicle and tucked up higher than the front one. The front one was shaking like an epileptic having a seizure and sounded like it had marbles rolling around inside of it. With the vehicle off I can smack that cat and hear things rattling around inside it, the other cat does not mimic this. I figured "ok the cat blew apart on the inside and it's done".

I was able to limp it to a Pep Boys that was a couple of blocks away and they read the codes for me. It came back with a MAF sensor fault and a multiple cylinder misfire fault (didn't see the actual fault code numbers) but nothing cat related which absolutely shocked me.

I pulled the MAF out and one of the guys cleaned it for me and we put it back in and I took it for a spin around the block. The rattle was back (no shock there) but it wasn't as bad. The service engine light was now gone but the truck ran like crap. It was chugging and sluggish and after goosing the gas a little on a side street it died when I stopped at a stop sign. Started back up again and drove it back to Pep Boys and parked it.

I find it hard to believe that the MAF sensor would cause all of these problems but hey stranger things have happened. Pep Boys wanted $375 to replace the sensor but I know that I can get the part cheaper elsewhere and replace it myself in 5 minutes. They said I can do that and they'd reset the computer and codes for $45. Is that my best bet? I'm trying to avoid having to pay for a tow 60+ miles back home.

Can anyone give me some advice?

[aleekat]

Diagnostic codes are just that. Not a "replace this and it's fixed". Sounds more like you cat is plugged up.

[misfitt006]

Originally Posted by aleekat

Diagnostic codes are just that. Not a "replace this and it's fixed". Sounds more like you cat is plugged up.

That was my thoughts as well. When the MAF code popped and the guy immediately went to "change the MAF" without any kind of troubleshooting I was very skeptical.

To me the rattle is a more pressing issue than the fault code.

If the cat is plugged and I pulled the upstream O2 sensor out, would that let that side of the engine breath enough to limp it home 60 miles?

I live in CA so a bad cat is the absolute last thing I wanted to hear out of a vehicle I just got since CA cats are ridiculously expensive and you can't buy a used one from pick n pull or someplace like that.

[j cAT]

Originally Posted by misfitt006

That was my thoughts as well. When the MAF code popped and the guy immediately went to "change the MAF" without any kind of troubleshooting I was very skeptical.

To me the rattle is a more pressing issue than the fault code.

If the cat is plugged and I pulled the upstream O2 sensor out, would that let that side of the engine breath enough to limp it home 60 miles?

I live in CA so a bad cat is the absolute last thing I wanted to hear out of a vehicle I just got since CA cats are ridiculously expensive and you can't buy a used one from pick n pull or someplace like that.

with the black smoke and runs like crap I would check out the distributor. a 1999 with 100,000 miles //// maybe it has 200,000 miles . you do a vehicle history check ?

then you could also check the fuel pressures/test procedure for proper pressures and any injector/regulator failures.

the cat converter will cause a loss of power / mpg loss..black smoke ? NO!

the rattle sound should be better checked ..could be exhaust /transfercase/u joints /rear end /brake clips/pads on and on.....

[misfitt006]

Originally Posted by j cAT

with the black smoke and runs like crap I would check out the distributor. a 1999 with 100,000 miles //// maybe it has 200,000 miles . you do a vehicle history check ?

No I didn't do a check, but it does have the old style 9 number analog odometer not a digital one so is there still a chance of it having more miles than it shows? I'm not sure of the reality of having odometers rolled back anymore like they were way back in the day.

Originally Posted by j cAT

then you could also check the fuel pressures/test procedure for proper pressures and any injector/regulator failures.

How would I do these checks? I'm just trying to get it home at the moment so I can troubleshoot somewhere other than a parking lot 60 miles away from home lol.

Originally Posted by j cAT

the cat converter will cause a loss of power / mpg loss..black smoke ? NO!

The exhaust smells really rich, so I think the black smoke was caused by the MAF sensor fault and the misfires. The black smoke is gone, I never saw it all the times I was working on it yesterday.

Originally Posted by j cAT

the rattle sound should be better checked ..could be exhaust /transfercase/u joints /rear end /brake clips/pads on and on.....

The rattle sound is definitely the cat. I was underneath the vehicle while it was running looking right at it as it was rattling. After shutting it off I can smack the cat with my palm and recreate the rattle, at a far lower volume and frequency of course but the exact same sound.

[aleekat]

The cat rattle may be something that happen to me on another vehicle. Rocks had gotten in the heat shield surrounding the cat and rattled.

[misfitt006]

Originally Posted by aleekat

The cat rattle may be something that happen to me on another vehicle. Rocks had gotten in the heat shield surrounding the cat and rattled.

That would be awesome news! CA cats are ridiculous. Would that cause the violent shaking that I saw though?

[j cAT]

the excessive rich running will damage the cat converters. this is usually a bad injector or regulator. using a pressure gauge [autozone has then most times] you can do the pressure test procedure. engine off ignition on the pressure should rise quickly to 62-65 psi and hold for a few min. if the pressure falls off rapidly this may mean the leak is in the injectors/regulator/or the pump check valve. to determine if it is the pump you have to connect to pressure guage to the pump output at the filter then the pressure should rise to above 65 psi and hold..could go up to 75 psi or more...[no reg]...

if it holds then you have a fuel injection/regulator failure with the fuel pump test holding press.. ..

another test is to start the cold engine . then go under the vehicle and place one hand on each converter ..the one that gets hot first is the bad side with too much fuel and this should get real hot as the engine warms. could cause odors as well and the heat shield to get distorted etc....

this could be caused by a fuel filter that was not replaced . the filters can break up when they get restricted and then foul the injectors.

the cat converters normally do not do anything. when unburned fuel gets to the converters this is when then start to heat up and begin the burning of the unburned fuel. this is when they melt down and cause problems.

I know of a person that replaced his converter on an old 10yr plus vehicle because he had a high HC reading. I told him to fix the injection problem first. he instead changed the cat converter. well the new converter got so hot the vehicle caught fire. then this was the end of his problems with that vehicle !

still could be the ignition/distributor or even a plug wire fell off burned up etc..

the MAF being cleaned will not cause a condition like you had ...now if the MAF had a total failure then that would be possible. also leaks in the intake ducts to the throttle body will mess up the mixtures and give false MAF codes.

best report the codes taken from vehicle ALL.... this gives the forum members a better handle with whats going on...

odometer changes are common. if you got this from a dealer and that odo was changed you can get your money back and perhaps damages with the expenses to purchase this...etc...if the dealership does not give you your money back on this with the odo changed then tell them you are to report this to the feds...

[misfitt006]

Ok I got it home!

I went up there today and disconnected the battery for awhile and then took it for a test drive (after hopefully clearing the faults from yesterday). It ran...'ok'...for a few blocks and then it started chugging again.

The Pep Boys tech checked the vacuum pressure for me when I told him I thought I had a plugged cat and he said the pressure looked good (he plugged his gauge into the EGR line going into the valve cover). He revved the engine at the throttle body and it blew grey/white smoke out of the tailpipe and then died at which time he said "yeah it's the cat".

Without giving me any 'official' advice he told me that they rent tools, specifically a tailpipe cutting tool, and if I were to utilize that tool I could drive it home no problem.

I cut the cat off and when I picked it up the ceramic guts came tumbling out of it. Catastrophic failure of the catalytic converter. One side of it had honeycomb in there sideways and the other side was completely open which was the side that had the pieces falling out of it.

You can't buy a used cat in CA and none of the <$100 cats you can buy online are CA legal so I called Napa and they've got one in stock for $284 (which I don't have).

Is there any 'JB Weld' type product out there that would hold up to the heat of an exhaust so that I could install the new cat myself or does it absolutely NEED to be welded in?

Originally Posted by j cAT

the excessive rich running will damage the cat converters. this is usually a bad injector or regulator. using a pressure gauge [autozone has then most times] you can do the pressure test procedure. engine off ignition on the pressure should rise quickly to 62-65 psi and hold for a few min. if the pressure falls off rapidly this may mean the leak is in the injectors/regulator/or the pump check valve. to determine if it is the pump you have to connect to pressure guage to the pump output at the filter then the pressure should rise to above 65 psi and hold..could go up to 75 psi or more...[no reg]...

if it holds then you have a fuel injection/regulator failure with the fuel pump test holding press.. ..

I know of a person that replaced his converter on an old 10yr plus vehicle because he had a high HC reading. I told him to fix the injection problem first. he instead changed the cat converter. well the new converter got so hot the vehicle caught fire. then this was the end of his problems with that vehicle !

still could be the ignition/distributor or even a plug wire fell off burned up etc..

Thanks for this information! Will these tests still be accurate with the cat being removed like it sits now? I'm nervous about replacing the cat only to have it happen again if there is an underlying problem that caused the cat to fail in the 1st place.

To do the pressure test where does the gauge get plugged in? Just any vacuum line or does it have to be a specific one?

Also, knowing I had one cat that had a catastrophic failure, should I change the other one anyway? Or can I wait to see if the other one will fail since they are so damn expensive in CA.

[j cAT]

Originally Posted by misfitt006

Ok I got it home!

I went up there today and disconnected the battery for awhile and then took it for a test drive (after hopefully clearing the faults from yesterday). It ran...'ok'...for a few blocks and then it started chugging again.

The Pep Boys tech checked the vacuum pressure for me when I told him I thought I had a plugged cat and he said the pressure looked good (he plugged his gauge into the EGR line going into the valve cover). He revved the engine at the throttle body and it blew grey/white smoke out of the tailpipe and then died at which time he said "yeah it's the cat".

Without giving me any 'official' advice he told me that they rent tools, specifically a tailpipe cutting tool, and if I were to utilize that tool I could drive it home no problem.

I cut the cat off and when I picked it up the ceramic guts came tumbling out of it. Catastrophic failure of the catalytic converter. One side of it had honeycomb in there sideways and the other side was completely open which was the side that had the pieces falling out of it.

You can't buy a used cat in CA and none of the <$100 cats you can buy online are CA legal so I called Napa and they've got one in stock for $284 (which I don't have).

Is there any 'JB Weld' type product out there that would hold up to the heat of an exhaust so that I could install the new cat myself or does it absolutely NEED to be welded in?



Thanks for this information! Will these tests still be accurate with the cat being removed like it sits now? I'm nervous about replacing the cat only to have it happen again if there is an underlying problem that caused the cat to fail in the 1st place.

To do the pressure test where does the gauge get plugged in? Just any vacuum line or does it have to be a specific one?

Also, knowing I had one cat that had a catastrophic failure, should I change the other one anyway? Or can I wait to see if the other one will fail since they are so damn expensive in CA.

with what I get is your level of vehicle repair you best have the engine checked out for the cause of the cat converter to melt down. the dealership sold you a damaged vehicle....