Blowing through cats

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wegsleepregeling

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Location
San Francisco
Ram Year
1999
Engine
v8 petrol
Shortly after I bought my beater 1999 2500, the catalytic converter failed after I gave it the beans on the freeway.

I had a new one put in for a quick $300.

Then I put the truck through its paces in anticipation of a trip. Towed a boat to and from Tahoe (from sea level), towed my camper to and from Tahoe (6000 pounds, from 4000' over 7000' to 5000' and back). It went fine, pretty much. Not a lot of power, but it's an old truck and only cost me $700.

Then on my trip, with the camper, passengers, and cargo, it finally crapped out. Same thing, the cat fried. This is just a couple thousand miles later. Got a blinking CEL just before/during the cat fail.

The truck also has the typical vacuum leak symptoms, making for quite a comfortable trip across the sweltering deserts of Nevada (heh).

Obviously, something upstream of the cat is running poorly (too hot?) and that's killing the cats. I get no codes.

Any suggestions? I certainly want to dig into that problem before putting on a new cat! And even if I register it in a county without smog check requirements and forego the cat altogether, I still need to fix this problem. Truck has the full factory tow package.

Thanks in advance!
 
Last edited:

muddy12

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Just spitballing here;

Vacuum leak could be causing the air/fuel mix to be off. O2sensor will see a vac leak as a lean condition, and will dump in more fuel, causing a rich condition in the exhaust. All that extra fuel being burnt off by the cat can cause it to overheat and burn out.




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Fast69Mopar

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When the check engine light starts flashing it means there is a Catalyst Damaging Misfire. A vacuum leak will cause a misfire. Check the plenum gasket and all around the base of the intake manifold. I would also check all of the vacuum lines.

The easy way to check the plenum gasket is by pulling the large rubber line off of the breather that is mounted on top of the throttle body and feel how much vacuum is being pulled there. If the plenum is leaking really bad you will be able to hear the vacuum sucking through the end of the hose and it will pull a hard vacuum on your thumb while covering the hose. The hose I am referring to connects to the breather and the rocker cover.
 

madtrucker2016

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need to change the o2 sensors I think you have four of them and buy the special socket for that it works great. Also you will get better gas mileage on the truck and maybe run smoother. I had a 04 Ram and changed all four made a big difference in the performance.
 
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mfelthousen

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Check and clean your IAC valve also or replace it altogether since it isn't expensive. The lack of codes is concerning considering how there is clearly an emissions issue. Chances are the O2 sensors are shot now (if they weren't before), and should be replaced as mentioned already.

I recently tried upgrading to 4-hole injectors on my '96. It ran fine for the first 50 miles, then would start stumbling and throw codes for running rich. I could reset the codes by pulling the battery lead, but the issue would come back. After a few cycles of this I finally went back to the original injectors (after cleaning them). I later noticed that when installing the new injectors I had pinched an 'o' ring and it rolled up a bit on the pintle. By that point I was tired of messing with the fuel rails and didn't bother putting the new injectors back in. That slight pinch caused a pretty impressive buildup of soot in the exhaust in a short time, so vacuum leaks in general could be the majority of your issue.
 

dapepper9

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need to change the o2 sensors I think you have four of them and buy the special wrench for that it works great. Also you will get better gas mileage on the truck and maybe run smoother. I had a 04 Ram and changed all four made a big difference in the performance.
*2
Check and clean your IAC valve also or replace it altogether since it isn't expensive. The lack of codes is concerning considering how there is clearly an emissions issue. Chances are the O2 sensors are shot now (if they weren't before), and should be replaced as mentioned already.

I recently tried upgrading to 4-hole injectors on my '96. It ran fine for the first 50 miles, then would start stumbling and throw codes for running rich. I could reset the codes by pulling the battery lead, but the issue would come back. After a few cycles of this I finally went back to the original injectors (after cleaning them). I later noticed that when installing the new injectors I had pinched an 'o' ring and it rolled up a bit on the pintle. By that point I was tired of messing with the fuel rails and didn't bother putting the new injectors back in. That slight pinch caused a pretty impressive buildup of soot in the exhaust in a short time, so vacuum leaks in general could be the majority of your issue.
The 4 hole injector thing is a bust. It's been disproved for years that it's not actually an upgrade but unfortunately people don't post on forums about it. All you'll find is that it is an upgrade and too many have been mistaken and made their truck run worse. Usually people would go 1 step bigger and the "gain" they felt was from over fueling in open loop
When the check engine light starts flashing it means there is a Catalyst Damaging Misfire. A vacuum leak will cause a misfire. Check the plenum gasket and all around the base of the intake manifold. I would also check all of the vacuum lines.

The easy way to check the plenum gasket is by pulling the large rubber line off of the breather that is mounted on top of the throttle body and feel how much vacuum is being pulled there. If the plenum is leaking really bad you will be able to hear the vacuum sucking through the end of the hose and it will pull a hard vacuum on your thumb while covering the hose. The hose I am referring to connects to the breather and the rocker cover.
^^pretty good info here
 
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