05 Silverado possible CAT problems

My son's 05 Silverado 4.0L with 75,000 miles will almost not run. Start it up and take off down the road fine for about 2-3 minutes then the trouble starts. Idle is rough. Can press gas peddle to floor while sitting still and will never rev above 3,000 RPM. Small hill in driveway that takes 4WLow to get up. Driving on road and pulling hill slows to alost a crawl with massive misfires and very strong raw gas smell in cab as well as cars behind smelling. Took it to Advance Auto to check engine lights. Said it was 02 sensor. Took it to dealership who said it was bank 1 & 2 02 sensors, maf sensor, rotor & cap but CAT's were fine. Have replaced plugs, wires, maf sensor, rotor & cap but still no changes. Holding off of 02 sensor due to money. I think it's the CAT. When you drive the truck for a very short time the CAT's glow bright red. Driving behind the truck in cold weather and watching the exhaust, it never changes from idle to hard pull. The same amount of visible exhaust come out. Gas milegae is shot...it sucks the gas. Takes almost 1/4 tank to go about 15 miles. Also have a lot of noise in cab when pulling hill. Gets to the point you can't even hear the radio. Noise sound like it's coming back up around the breather. Can the 02 sensor cause all this or are the CAT's stopped up? If the CAT's are stopped up how do I get the dealership to fix them when they say nothing is wrong with them. I know the CAT's are still under warranty. At this point the truck is off the road and not driveable. Any ideas or suggestions? Thanks in advance for any help.

This is going to the Silv. forum below, for better responses. What was done at the shop to determine the cat was ok, did they do the required back pressure test? You did the work they suggested and it was still not fixed, if they did the work, I would drop the car back in their lap for a proper repair

Emissions warranty is good for 7-years!

Emissions warranty is good for 7-years!


it's actually 8 years 80,000 miles

Correct, Calif emissions are 7/70 all the others are 8/80.

I'm guessing read codes from the computer. They rattled off the long list with repair prices then said they had to fix all of these first, clear the codes and drive it down the road to see if other codes come up. After I choked over the price and long list I picked up the truck and told them I'd have to save the money before it could be fixed. Came home and did all repairs ourselves except for the o2 sensors. Ran out of money at that point. They also told me I needed front brakes and that the pads were completetly gone and into the rotor which would need replaced, not turned but replaced. Checked on the brakes when we got back home and they have slight wear but no where near worn out.

I'm guessing read codes from the computer. They rattled off the long list with repair prices then said they had to fix all of these first, clear the codes and drive it down the road to see if other codes come up. After I choked over the price and long list I picked up the truck and told them I'd have to save the money before it could be fixed. Came home and did all repairs ourselves except for the o2 sensors. Ran out of money at that point. They also told me I needed front brakes and that the pads were completetly gone and into the rotor which would need replaced, not turned but replaced. Checked on the brakes when we got back home and they have slight wear but no where near worn out.

TAKE THE O2 SENSORS OUT [HOLES OPEN] GO FOR TEST RUN....

if it runs better , the cat converters/exhaust system is plugged....

question is WHY at 75,ooomi did the converters go bad ????

without repairing the cause the new converters will soon fail as well..

the rich mixture baked the cats. the truck overfuelled...from bad 02 or maf??...excess fuel into cat's (you smelled fuel).... the cat tried to oxidize/reduce the unburned fuel and heat build up from the process melted the cats...ie glowing red. Cats probably are plugged now.

the 02 cross counts from front and rear 02 sensors are one way cat's are checked (temp in and temp out, tap test and back pressure are the others). Maybe that's how the dealer checked them; maybe didn't set code due to failure of front 02 sensors. How did the dealer determine cat's were ok?

If the mil was flashing when you were driving; cat damage is about to occur. flashing mil means shut it down.

I agree with jcat the overfueling must be repaired first or you will ruin new cats.

dtc, fuel pressure data and live engine datastream would be helpful to diagnose. Does the dealership workorder list the dtc's

Throw the list of suspected failures away, throw some codes @ AF.

dtc, fuel pressure data and live engine datastream would be helpful to diagnose. Does the dealership workorder list the dtc's


No dtc's listed on dealership work order. This is what they listed on workorder:
Check engine light is on advise repair...
Many codes stored
Codes for MAF sensor
Codes for misfire (rotor and cap)
Codes for 02 sensors/ both
Needs front pads and rotors

Recommedations:
Hass exaust leak...need other repairs listed first


If the mil was flashing when you were driving; cat damage is about to occur. flashing mil means shut it down.


Check engine light started flashing the other day after installing MAF sensor and taking out for test run. Engine shut it's self down just when turning in driveway at home. Rolled to a stop in driveway let it set overnight. Went out to check it the next day and it started up fine. Didn't move it just turned it back off and it's still sitting there. Have had nothing but trouble since the first week of owning this truck. Bought it used from a dealership with 18,000 miles on it. I guess I know know why 1st owner traded it. This is the first problem I've had that was not covered under warranty. Mostly it's been trans. problems and each time they fixed it I got another year of warranty and it would have to go back for repairs before that year was up. Finally had to have a new trans. I just want to get it fixed to trade or sell it. Want out from under the payments and the problems.

The money you paid for service, you could of bought a new AutoScanner.
Use AF, and Google 'Pcodes'

Focus on the most probable cause, one simple problem could generate several codes.

[quote=cdmonday;6096598]My son's 05 Silverado 4.0L with 75,000 miles will almost not run.
quote]

what does this vehicle have for an engine ? 4.oL is not an engine in this yr model...

Is this 4wd or 2wd ?

your sons problems at this amount of mileage is very unusual ...I would do a car fax search on the vin # ..it is possible its a scam...

[quote=cdmonday;6096598]My son's 05 Silverado 4.0L with 75,000 miles will almost not run.
quote]

what does this vehicle have for an engine ? 4.oL is not an engine in this yr model...

Is this 4wd or 2wd ?

your sons problems at this amount of mileage is very unusual ...I would do a car fax search on the vin # ..it is possible its a scam...

your right j cat. Now that you mention it...only 1 engine made for this yr/model has dist cap and rotor.

Try replacing the fuel filter. Same problem happened with my previous silverado, I replaced the fuel filter after going through a laundry list of other options, ran like a dream.

i am betting the first time the problem showed up, it was raining out side. change the cap and rotor it will go away. the 4.3l has a problem with the rotors arking in side and burning out.