when i worked at the garage we had a jeep grand cherokee come off the highway customer said it was losing power and couldnt get up to speed, ran ok at an idle but when u revved it it ran terrible, pulled it on the lift and all 3 cats were glowing red, 2000 bucks later and 3 new cats he was back on the road, after pulling the old ones off you couldnt see any light through them and u could see how clogged the honeycombs were

 

All three? Wow. Maybe getting off-topic here, but what do you think would cause something like that? That sounds like a pretty odd occurrence.

 

one or more of the many things that would cause your engine to run over rich. #1 reason, running higher than the specified octane for your truck, habitually.

 

Hmm, good to know. Thanks.

 

Sorry but I gotta disagree with ya on that one, Octane level has nothing to do with it.
Higher octane rating does not make a fuel burn hotter, only takes more to "set it off".

See here,

Octane rating - Wikipedia, the free encyclopedia

Higher octane tends to be a better quality fuel at least where I live, I run premium in dirt bikes, chainsaws, lawnmowers, boats just anything that isn't used regularly.
Regular no lead has a lot more impurities in it so does mid grade, if left to sit in a fuel system like a carb's bowl it settles gumming up the works.
Premium doesn't do that, at least not while a motor over winters unused until spring again.

I use the cheapest fuel I can get for the trucks regardless of octane rating, it goes through it like crap through a goose so its not in it long enough to hurt anything. That and its doesn't sit months at a time unused either.

 

Check the oil, if its dumping enough unburnt fuel in to cause the cat to glow red hot, your oil will/should be contaminated with fuel to.

Have a strong fuel odor to it, even watered down thin not slick because of it.

 

From you link:
Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.


I stated that running higher octane in an engine such as his (a low compression engine comparatively/ An engine specifically designed to run on 87 octane) Will run over rich when subjected to a habitual use of higher octane fuels (a result of residual incomplete ignition of the higher octane blend. 87 octane has the best "overall" easily combustive properties of all the normally used octanes. I never said anything about higher octanes running hotter in his application. In fact it would produce just the opposite, a quenching effect.

Which part do we disagree ?

 

Unless there is a misfire, the air/fuel ratio will not change between gasolines with different octane ratings. Higher octane fuel can tolerate more spark advance (with all else being equal) which can gain some torque, but as the wikipedia reference says, the fuel itself is not the source of the increase.

Who dug up this old thread anyway?

 

Which part do we disagree ?

Well the part where common pump gas, using premium rather then regular would or could make any difference as it pertains to this thread.

More to my point as stated above, the air/fuel mixture is not changed with the use of higher of lower octane, no btu change in effect so to speak.

Who dug up this old thread anyway?

Don't know, been away couple few days and didn't realize it was.

 

AS per ALLDATA
ISSUE: Rough idle, hesitation, poor throttle response, induction backfire and stalls during cold start/warm up may be caused by the poor volatility of some high octane premium grade unleaded fuels (91 octane or higher (R+M)/2). When compared to regular grade unleaded fuel (87 octane (R+M)/2), high octane premium grade unleaded fuel may cause long crank time.
ACTION: Use a regular grade unleaded fuel in all vehicles, except where a premium unleaded fuel is recommended in the Owner Guide. If lean air-fuel type symptoms are experienced, determine the grade and brand of fuel used and offer the following service tips.
^ Advise those using a higher octane grade fuel to switch to a regular grade unleaded fuel. For those using a regular grade fuel, advise them to try another brand.
^ Do not advise using a higher octane unleaded fuel than is recommended for that specific engine. Ford engines are designed to perform best using a high quality regular grade unleaded fuel.
^ Only advise using a higher octane unleaded fuel to avoid potentially damaging spark knock or ping, but do so only after mechanical fixes are ineffective.
NOTE: ALL UNLEADED GASOLINES USED SHOULD CONTAIN DETERGENT ADDITIVES THAT ARE ADVERTISED AS HAVING "KEEP CLEAN" OR "CLEAN UP" PERFORMANCE FOR BOTH INTAKE VALVES AND FUEL INJECTORS.
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 404000

Induction backfire?
This would now semantically qualify for use of the word "Overrich"? (maybe not, I think that's actually two words)

 

The most common cause for clogged cats is a rich mixture. The two most common causes for a rich mixture are a vacuum leak or old oxygen sensors. Either cause should light the Check Engine light on a Ford before the cats clog with carbon or melt down.

If the car has gone more than 60,000 miles since it got new oxygen sensors, they should be changed. Before doing that, look for vacuum leaks anywhere in the intake system. There can be other causes for unburned fuel igniting in the cats, like leaky injectors, but they are often rare. Pulling the codes can help diagnose the cause.

If you replace the cats but don't repair the cause of them filling with soot, then you run the risk of clogging the new cats and perhaps melting the matrices too. Glowing cats are a symptom, so don't overlook the original disease in your desperation for a cure.

Scott

 

If you have a timing light (harbor frieght $20), check the timing! It takes five minutes and can save you a whole lot of time and trouble. Or you destroy your CAT first and find out it was your timing later. Either way it's your call.

 

Another Fav is a pooched Fuel pressure regulator. Then there's proper injector function, or lack there of. and the list goes on!
True, if you don't address the cause, you will repeat the effect.

Sooooo! He never mentioned what flavor of octane he actually used! So, I guess we won't know what this particular cause was! Phantom threads exhumed from the past can be a real pisser, especially when the lack of eventual outcome tends to mute the arguments that develop.

 

well the Jeep had almost 300k miles on it

 

I had the cats taken off my truck today and replaced with pipe. The truck runs way better and sounds good too. It cost me 160 to have it done at a local muffler shop. I brought the old cats to the scrap yard and got 120 for them. Win win for me.