Loss of gas milage and rod ticking??

Lately, I have noticed a NICE drop in my gas milage. I am getting roughly 100 miles in a 1/2 tank full. NOT like it used to be, I was able to go atleast 150-170 per tank. If I somewhat get on it, I can actually watch the needle move down. I am running 87 and will try 89 and 93 on the next tank to see if that does anything.

Also, I have a piston rod ticking noise that I have noticed as well lately. If I lean down, right under the front of the oil pan, I can hear a tick-tick-tick, in no consistant order. I am not real worried about this as I have heard other I6s make different noises.

I am worried at only 83k on my 91 why its not decent gas milage and the wierd noises that I hear.

I am developing a small crack in my exhaust header, the cat needs replacement, and the muffler is not in the best shape. All this is soon to be replaced, but these items have been like that, the notice in milage drop just occured about a week ago.

Please let me know, I REALLY want this motor to last a LONG time.

Thanks.
TOEHEAD

That ticking noise could be coming from the crack in the header. That same crack could also be allowing some air into the exhaust, causing the O2 sensor to read a false high O2 content, so it thinks the A/F mixture is too lean, and tells the PCM to dump in more fuel. That could be why your gas mileage has gone down the toilet. A bad cat won't help either.
Fix these and I think the ticking will go and the gas mileage will improve.

Dr. Dyno said:

That ticking noise could be coming from the crack in the header.

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Really.........hum, that is VERY interesting a good to hear. I REALLY hope it is in deed that.

Like I said, I need to save just a few more pennies then I am going to replace the entire exhaust system.

Thanks.
TOEHEAD

Would the cracked header cause it to tick under a load or going up a hill??

Ive only got 83k on the XJ, hoping Im not going to have to rebuild it anytime soon.

thanks..
TOEHEAD

Yes. The ticking from a cracked header is worse under load and disappears on a trailing throttle.

TOEHEAD said:

Would the cracked header cause it to tick under a load or going up a hill??

Ive only got 83k on the XJ, hoping Im not going to have to rebuild it anytime soon.

thanks..
TOEHEAD

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Bennett, you know what my rig sounds like don't ya? That's what a cracked manifold sounds like.