I was wondering if there was anyway to check if a catalytic converter was clogged other than just replacing it or taking it off. I heard from a shop that if you hit it and it makes noise like theres something inside of it then it is clogged. I tried this and it made the noise but then I tried it on my moms brand new car and it made the noise to so now Im kinda thinking that they all make this noise. Is there anyway to check the compression of the cylinders and tell or anything like that. I have been getting really bad gas mileage (like 12city/16hwy with my 2.3l 5-spd) and have been trying everything to get it to get better gas mileage. I also noticed on my air filter there are two outlets for emission hoses and mine only has one attached and I cant find the other one. Would this make a big diffrence on mpg. thank you guys for your help

 

Vacuum leaks are a major cause of poor performance and mileage drops. I don't know what year you have but that one line could make all the difference. Doubtful though. If your truck is older than 95 and it has never had the cat replaced then it's probably due anyway.

 

Its a 94 2.3l 5-speed

 

Symptoms of a clogged cat are low on engine power and possibly higher than normal engine temp. You can hook up a vac gauge and take a reading; this reading can indicate the high back pressure caused by a failed cat. Age and/or mileage alone do not automatically mean a clogged cat. I've got 174,300 miles on mine and there is no indication of failure.

 

One good way to wipe out a converter is to have a bad miss and run the engine for a long time. The converter loads up with unburned fuel and gets so red hot that the ceramic cracks, making that rattling sound. Eventually the broken peices rattle around and get stuck sideways in the outlet of the cat, not allowing exhaust gas to escape.
Sort of like what I did to my 66 bug when I backed it into a drainage ditch and smashed the exhaust pipes so bad that no exhaust could get out. It ruined the motor.
A real mechanic can measure the back pressure, I think the limit is about 5 PSI. I have a home made tool the I made out of an old oxygen sensor, it screws into the oxygen sensor hole and has a vacuum hose fitting welded on it. I screw it in and hook a cheap old fuel pump gauge to see if there is any back pressure in there.
I agree with the other guy who said its more that likely a vacuum leak problem than a converter problem, but you will figure it out.

 

I'v never seen the second vacuum port on the air box used i just took for granted it was an extra. Is it idling higher than it did when the mileage was better, I just replaced the upper intake gasket on my 89 with a 2.9 and the idle dropped alot and the fuel mileage got better. While i had it off i removed everything from it and replaced the gaskets for the throttle body and a block-off plate. I also removed the vacuum trees and replaced them with loctite thread sealer.

 

On my 1989 2.9 the two vacuum lines at the air box were for the warm air inlet for cold weather, one goes to the intake manifiold and the other goes to the valve down by the frame on the passengers side. It's not really needed in most areas but you should plug the line at the intake to avoid vacuum leaks.

 

i used to have a buick grand national that was extemely powerful but it relied alot on the turbo and exhaust. well after a short period of time the car became very under powered and the turbo never kicked in i also lost alot of mpg. because i was all over it to get it to move. the cat was so badly burned up inside and crumbled that it was literally chocking the motor. i had that changed along with a full "hooker exhaust" system put on and it ran like a hot-rod should. huge difference, like two different cars. sorry guys for bringing a gm into the discussion.

 

You can check for an exhaust restriction using a vacuum gauge. Measure manifold vacuum at idle and then at 3000 RPM (hold it there a minute or so). If the vacuum at 3000 RPM is lower than at idle, you have a restriction. Up to about 3" is tolerable, more than that and you have a problem.

 

can you remove the o2 sensor thats before the cat and test drive it, to see if you have more power? the open hole would give exhaust a place to escape.

 

If you don't poison the catalytic converter with anti-freeze or RTV silicone, it can last forever. They do not wear out, they get killed. I still have one on my car that has 245k. The SMOG test numbers are still good, and it gets decent fuel mileage.
The culprits you could look for are 1)fuel pressure regulator 2)Air and coolant temp sensors (ACT & ECT), 3)your thermostat 4)ignition components 5)air cleaner 6)engine timing 7)all that extra cr*p you carry around in the back of the truck and 8)tire pressure. Not necessarily in that order, but some are easy to eliminate..
tom

 

I second that, my Dad's 1996 Ranger 2.3L has over 300,000 miles and still has the original cat. According to him, it also got 29+ mph on the last tank. A lot of people like to jump tot he cat as inhibiting performance and causing bad gas mileage, when in reality it is usually the opposite, something goes terribly wrong with the vehicles fuel management, causing poor performance and bad gas mileage, and it takes the cat down with it.

 

I screwd out oxy sensor and tried to rev engine up, then I drilled holes in cat (easy to weld) and finally realised that cat is really clogged.