repeated muffled backfire???

Danny did pass the time by typing:

That tube is your vacuum advance. Your timing is hosed. Time to start checking for cracked lines and if the vacuum pot has failed. This is for a Jag, but the concept is the same.

Dan,

That is the vacuum advance solenoid, and it sounds like the diaphragm inside may be leaking. Take the other end of the line off the carb, and suck on it. If you get any air through it at all, that's it, simple and cheap. Also check the line itself for a hole or dry rot.

Dan

Ouch.... That engine's timing is also controlled by a computer....

Do you still have the emissions computer running things?

But anyway, the timing is also vacuum and mechanically controlled. That line is the vacuum advance. You should be able to take the line off the carb and suck on it and it should hold vacuum.

Inside the distributor is a base plate that needs to be lubricated. The oil pad for it is under the rotor. You pull the rotor off and oil the center of the shaft with 10W30 oil, then work the plate.

You should be able to grab the rotor and turn it. It should be heavily spring loaded and spring back into place fast when you let go.

If you suck on that vacuum line when the distributor cap is open, you also should see the base plate move or at least you should be able to move the vacuum advance linkage with your fingers.

Check that stuff out and get back to us. There are more things to 'play' with, but the 'basics' need to work first.

Mike

ok... it took way too long to get the new vacuum advance..but i got it...then i decided it would be a great idea to round off the head of the bolts holing the old advance down...not such a great idea...2hrs later i'm able to get those out but anyways... i install a new vacuum advance/distributor cap/rotor button...reset the timing...and the backfire is still there..a friend has told me it might be the Catalytic Converter...is this a possibility?? if not any other ideas??

Mike Roma> Ouch.... That engine's timing is also controlled by a computer.... >

Did you make sure the mechanical advance was working by manually twisting the rotor to make sure it twists smooth with a strong spring load back? This is a different animal than the vacuum advance.

Do you have the computer still running the timing? If so did you set it by the emissions label directions?

You should be able to get an idea of the cat's condition using a vacuum gauge I think. We are lucky here in Canada, CJ's didn't come with cats up here.

I also think an air leak into the exhaust can cause backfire. Is the manifold nice and tight? Might be worth putting a wrench on it to see.

Mike

Danny wrote: