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86 cj7 258 no power accelerating and air leak sound.

86 cj7 258 no power accelerating and air leak sound.

rockhounder

Jeeper
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Location
Phoenix, AZ
Vehicle(s)
1986 Cj7 Laredo 258 bone stock,
2000 F350 4x4 CC 7.3l Diesel
Hi everyone, new guy here.

Background on my Jeep: Completely stock. All the emissions stuff is still installed. 71k orig miles. Jeep has been garaged for the most part for last 20 years.

My jeep was running great after I did a tune-up to get her thru emission testing. I started to feel a loss of power one day when I would accelerate into 2nd and 3rd gears. So I took a drive on the freeway thinking I would get up to a higher speed and see how she ran. I heard an air leaking sound develop and I couldn't keep power up.

I went back to my garage and confirmed my timing was correct and checked for electrical shorts and vacuum leaks but all was good from what I could tell.

I now have a loud whooshing sound coming from under the drivers seat. I started reading in here about the catalytic converter problem and it sounds like that may be my issue.

So do I remove my cat to see if she runs better? I'm not sure if there is an easier way to test it? If anyone knows of a good thread already out there that explains what to do that would be great.

Thanks in advance.
 
I had my cat replaced years ago and was given a straight thru version, which is legal, even here in the original land of smog. With that I got the next size up pipe and a performance muffler. Other than a possible stuffed up cat, you might have other problems also. The emissions system that came with '86 is a real can of worms and everything has to work.
 
Thanks Torxhead, I appreciate the reply. I'll check into the straight thru version of replacement cat converters. Here in Phoenix we have the tough emissions testing too so I'm going to need to keep a cat on there.

I've read a number of threads on this issue but most of them don't state what the outcome was. I wish more people that ask for help would follow up and tell us how the problem was resolved. :(

From what I've read so far I think the cat has to be cut off instead of un-bolted? I'll have to get underneath and take a look. I was hoping for a quick check to see if I could determine the cat had indeed failed.

I'll keep digging and post my results.
 
you can try unbolting the exhaust at the manifold flange and give it a test run that way.. will be very loud but should let you know if its the cat or not..
 
What kind of emissions laws does AZ have?

On most of these mid 80's Jeeps, the nutter bypass with no cat will make the Jeep run MUCH better, and actually lower emissions. You get all the stuff stopped up and/or not working and you'll end up blowing huge clouds of smoke out the rear. Mine got so stopped up I had to feather the throttle to get it moving, and if I floored it and let off I'd get a nice big backfire (was great for tailgaters).
 
you can try unbolting the exhaust at the manifold flange and give it a test run that way.. will be very loud but should let you know if its the cat or not..

Good idea! I'll give that a try.

wm69, I'm not sure exactly what the AZ emissions laws are. I need to dig in and finds out what I'm allowed to modify.

Maybe someone else in here from AZ has some good info on what is allowed?

Thanks again for the help!
 
Rockhounder, a visit to a local smog shop should get your questions answered, if not try another smog shop. A muffler man should also know what is required. I didn't even know that AZ had smog testing.
 
A weak/low vacuum gauge reading would indicate plugged exhaust.
 
you can try unbolting the exhaust at the manifold flange and give it a test run that way.. will be very loud but should let you know if its the cat or not..

Thanks! :notworthy:

I did what you recommended and what do you know? It was the cat.

I did a before and after video to show how bad the clogged cat was effecting engine performance.

You were also right, it is loud! I kinda like that sound, not sure if I'll be happy with a quiet exhaust again.

Video link:

1986 CJ7 with the clogged Catalytic Converter Problem - YouTube

Thanks again to everyone for all the help! :chug:
 
What kind of emissions laws does AZ have?

On most of these mid 80's Jeeps, the nutter bypass with no cat will make the Jeep run MUCH better, and actually lower emissions. You get all the stuff stopped up and/or not working and you'll end up blowing huge clouds of smoke out the rear. Mine got so stopped up I had to feather the throttle to get it moving, and if I floored it and let off I'd get a nice big backfire (was great for tailgaters).

wm69, Arizona has tough emission laws. Inspection and testing is required in Phoenix and I think Tucson too. Some of the counties are exempt from testing.

I'll have to check into what I'm allowed to do here. I would like to do the nutter bypass if possible. I also have to check into what I am allowed to do with my exhaust now that I know my cat has failed.

I've been searching threads in here for more info but so far I haven't found much.
 
Rockhounder, the Nutter bypass will eliminate computer operation of the carb and dist. If you go for an emmissions test setup like that chances of failing would be iffy at best and you will not pass without the cat.
 
Before you remove the cat look for vacuum leaks. If you have the stock carb that might be your problem. Every Jeep I have owned had a vacuum leak and a Weber solved the problem
 
Rockhounder, the Nutter bypass will eliminate computer operation of the carb and dist. If you go for an emmissions test setup like that chances of failing would be iffy at best and you will not pass without the cat.

Thanks, good to know. I don't think I'll do the nutter mod until I can figure out if it would pass emissions.

Before you remove the cat look for vacuum leaks. If you have the stock carb that might be your problem. Every Jeep I have owned had a vacuum leak and a Weber solved the problem

Thanks. Before I removed the exhaust pipe at the manifold I checked for vacuum leaks with some carb & choke cleaner. I inspected all the vacuum hoses and noticed that the hoses on the air filter housing was brittle. Also the hose to the distributor was questionable. So I replaced the hoses. I noticed a better idle but she still ran like :dung: with no power.

After I removed the exhaust pipe from the manifold she ran like new.

Now I have to see if I can change the cat myself or if I have to take it to a shop. I don't like anyone else working on my jeep. So I'm hoping I can do it myself. :)
 

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