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-   -   Catalytic converter/engine compression (http://www.wranglerforum.com/f218/catalytic-converter-engine-compression-147068.html)

deepak 03-18-2012 03:39 AM

Catalytic converter/engine compression
 
i own a 92 jeep renigade with straght 6, with 231j gear, 35 inch mickey thompson tires and no lift and 138000 miles, brand new boshch platinum 2 spark pugs, new wires, new rotor and rotor cap,, just replaced engine oil with mobil, replaced both tranny and transfer case oil,,gives about 10-12 mpg :( the problem that i am having at this point it that jeep works fine until 3rd gear, when i go to 4th gear i feel loss of power just a little bit when i shift from fourth to 5th gear around 2.25 rpm and above 50 miles the speed starts decreasing to 45 and it just gets stuck there. i just doens't go above that and a 1.5 rpm even with full accelerator..im assuming it's caused by bad engine compression or bad cat converter.. i haven't gotten the compression checked yet but will get that asap.. and ideas why it's going on...:banghead::dance:

Beachcruiser 03-18-2012 08:51 AM

The cat is definately a suspect, compression is easy to check, but 35s w/ stock gearing is going to kill your top end too...

Gkrynick22 03-18-2012 08:51 AM

I don't think a bad cat would cause those symptoms. If your cat was bad the jeep wouldn't rev properly and would lose power no matter what gear you were in. Some times a clogged cat won't show its symptoms until it warms up. I would check the compression.

Master4th 03-18-2012 10:04 AM

Hows your clutch, do you smell anything when this happens?

kik 03-18-2012 12:21 PM

Quote:

Originally Posted by Gkrynick22 (Post 2152445)
I don't think a bad cat would cause those symptoms. If your cat was bad the jeep wouldn't rev properly and would lose power no matter what gear you were in. Some times a clogged cat won't show its symptoms until it warms up. I would check the compression.

I'm going to have to partially disagree on this. When the cat on my 89 4.2 5 spd. was clogged it ran fine with no problems until it got to about 40-50 mph when you would be in 4th or 5th gear. At that point it still ran fine except that it "dogged". No additional power even when you pushed it to the floor. And, it basically died in place going up hill. Changed the cat and everything was back to normal.

deepak 03-18-2012 01:59 PM

i put brand new clutch.. and by top end im sure you are referring to head, valves, and rings?

deepak 03-18-2012 02:01 PM

and sugggestions about gas mileage?

Beachcruiser 03-18-2012 02:48 PM

I'm not sure how you are fitting 35s on a no lift YJ (unless the fenders are trimmed a LOT)...but if you have the stock gears your mileage is probably going to suffer a bit as more throttle will be needed to get you away from a dead stop. You could swap in 4.10 gears from a 4-cylinder Jeep for pretty cheap. It won't get you to 20MPG, but combined w/ easy driving, it would probably help.

Big tires & good gas mileage don't really go together.

Master4th 03-18-2012 05:30 PM

Quote:

Originally Posted by kik (Post 2152861)
I'm going to have to partially disagree on this. When the cat on my 89 4.2 5 spd. was clogged it ran fine with no problems until it got to about 40-50 mph when you would be in 4th or 5th gear. At that point it still ran fine except that it "dogged". No additional power even when you pushed it to the floor. And, it basically died in place going up hill. Changed the cat and everything was back to normal.

Ditto on that, same thing happened to me accept eventually the chunk that was clogging totally clogged my exhuast and it was like the engine was working way to hard but I wasnt going anywhere.

Gkrynick22 03-18-2012 07:54 PM

Quote:

Originally Posted by Master4th

Ditto on that, same thing happened to me accept eventually the chunk that was clogging totally clogged my exhuast and it was like the engine was working way to hard but I wasnt going anywhere.


I stand corrected, twice. I have never seen a clogged cat that didn't have an effect in every gear. It's good to know though. Did you get a chance to check the compression?

deepak 03-19-2012 01:46 AM

no i haven't gotten the comression checked yet.. illl post the results as soon as i get it and also im gonna try it withouut the cat.. as soon as i do it .. the results will be posted.

gmcnutt13 03-19-2012 02:35 PM

Id almost bet you just need to re-gear it. I have a 4.2 5 speed on 32" tires. And i cant even use 5th gear unless i am going down hill. And 4th is at about 2,200 RPM's at 55 or 60 MPH. And going up a steep hill in 4th is almost worthless unless i get a good run at it. lol. Unless i have a clogged cat or something also.

gmcnutt13 03-19-2012 02:43 PM

Oh and i have the stock 3:07 Gear ratio :(

deepak 03-20-2012 01:09 PM

The compression test passed..so I need to re gear it and time for new cat

4bratsdad 03-21-2012 01:20 AM

mine was doing the same thing i have a 2.5 w 32'' tires, i have got it up to 65-70 a couple times on not so windy days downhill but have never been able to use 5th gear,found out my cat had been gutted so i did new cat back yesterday, it ran better , more power, and then clutch went out today and it wasnt even slipping

gmcnutt13 03-21-2012 11:39 AM

Your cat being gutted actually caused a loss in power? I know engines need back pressure to run properly but i would figure that the muffler would be plenty. I need to check mine out.

deepak 03-21-2012 04:19 PM

im just gonna take out cat and check what happens.. :)

2fastc 03-22-2012 12:49 AM

just start it and fill the exhaust coming out of the tail pipe if it fills like a soft breath it is clogged if you can fill it sputter it probably ok.

J20 03-22-2012 12:24 PM

Has your 92 always done this or did it just gradually start losing power?

4bratsdad 03-22-2012 09:10 PM

if im right the o2 sensor measures the exhaust flow and if the converter isnt there to slow it down a bit , it tells the computer to give your engine more fuel to compensate ,causing it to run richer -using more fuel, mine seemed like it had more pep after i installed the new cat muffler and tailpipe, i havnt really been able to check mileage yet cant replace my clutch till wed, my buddy had a f-150 v8 could spin rear tires on dry pavement took his out and couldnt spin them anymore and used extra 30 bucks a week in gas, put it back on thing went back to norm, i think removing the cat only helps on pre computer vehicles, my opinion


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