alright ive been chasing this problem for about 6-8 months. my check engine light code says "catalytic converter efficiency low" so. I replaced the CAT.... still having problems... some days it will run fine, others it will run like its about to die, IF it runs at all!!!!! it back fires every so often, has major horse power loss, like I can barely go over 30 mph sometimes, and once I do get u to about 25 or 30 it wont shift into the next gear, it just revs up but doesn't shift or gain speed. it is eating up gas more than ever, maybe getting 6-8 mpg. I know the ignition coil is out which is causing it to have problems starting, but that's getting fixed soon. im starting to think the cat I put on it is too small? I went cheap and baught it off a website, and when I replaced it, I noticed the one I put on there is maybe a half to three quarters the size of the bad one I took off... could this be the problem? it said the cat was for my make model n year of jeep, but I dunno if it being so much smaller could be making these problems continue.... should I just fork out the 200 bucks to buy another CA or what? any suggestions would be greatly appreciated!!!! I am legally disabled and require my car to see my doctor and hospitals etc... so having my jeep run like crap, if it runs at all, is ruining my life! thank you to anyone who can give me suggestions or things to check. (btw ive also replaced both of the 02 sensors and the crankshaft position
Since you said it's that small, I would go ahead and eat the money for the right size cat. I would also have the O2 sensors checked to make sure they are working correctly. Like I said though, I would start with the cat. Good luck and hopefully someone else has helpful input as well!
1995 ZJ, 5.2L, NP249, stock suspension, e-fan, CAI, engine needs work!! Plan on lift and tires when money finds its way here...
a misfiring engine will ruin a cat if left uncorrected. If you know the coil is bad, replace it. if you have never changed the o2 sensors or have Bosch sensors installed, it's time to get those replaced too.
Additionally, if your ZJ still has the factory manifold, it is more than likely cracked. If so, the PCM will enrich the fuel mixture and over burden the cat, decreasing its service life.
Aftermarket cats are often physically smaller than the factory or even older aftermarket cats. I know my Magnaflow 2.5" high flow cat was shorter and thinner than the bad older aftermarket cat that was in there. If the pipe is the same diameter as the rest of the system I wouldn't worry about the catalyst dimensions. It has to be pretty blocked before it causes symptoms as bad as yours. I'd say if you know your coil is bad start there, it could be all that's wrong.
I dont remember what brand.the.02s.are?. If its simply bad oxygen sensors, could it really cause all these symptoms? Also, does anyone know of a place i could take the.oxy.sensors.to.test n see if they are failing or if theyre still good? .. what would it mean if i do unplug the sensor and it.DID make it run better?..which one do i unplug? Upstream or downstream sensor? I just replaced the ignition coil yesterday and it fixed one of the.problems (one that just started recently, car.not wanting to start sporadicly) but its still having all the problems i origionally listed.
the o2 sensors are on/in the exhaust pipe. when you find appendages with wires protruding from the pipe, you're home free.
to tell what kind of sensors it has, crawl under there with a rag, mirror, and light, clean them and do a close examination of the sensors. if you see any numbers or brands, write them down and post them. if they are Bosch, go ahead and change them.
the front sensor is located just below the exhaust manifold in the exhaust pipe. unplug the front sensor. the connector is under the intake manifold on the side of the engine block. if it makes it run better, remove and replace the front sensor.
there are two ways to test o2 sensors, one is with a scan tool and the other is on a bench with a propane torch. these are periodic maintenance items that should be changed every 100k. it will cost you more to have them checked than to change them.
Is the Muffler stopped up? The membrane from a bad cat can stuff one up in a heartbeat! The installer should have checked for debris when he changed it, but it sure sounds/indicates that that muffler is stuffed!
The muffler seems to be fine. The exhaust.comes.out just fine like.it should.and theres.no liquid coming out of it... i changed the 02 sensor about 5 months ago when i changed the CAT (about 40k mikes ago) so it shouldntnt be out. But ill take it off n see if it runs better
Thanks for the suggestion.