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Unread 05-29-2002, 04:14 PM   #1
KG4PAM
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Location: Lenoir City, TN
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decreasing gas milage

when i first started driving my cj a lot(a month ago) i got 14.9 mpg regularly for probably 3-4 tanks. all of a sudden, it went down to 12.3, again for a couple of tanks. when i calculated the last time(day before yesterday) it was down to 11.9. What is happening????? what can i do to increase power/milaege? power b'cuz it seems to have an extreme lack thereof. the jeep dosent smoke, but there is a slight gas smell which gets annoying. i was going to put a cherry bomb on to hopefully reduce backpressure, but it was too long to fit without changing a lot. help !!

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'81 CJ-7 Got it when I was 16!
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Unread 05-29-2002, 05:21 PM   #2
buddhasbomb
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if you smell gas then theres a leak somewhere.you didnt say if you chcked tire pressure,possible dragging brakes,or ,like in my case,a snot nosed brat next door needed gas for his honda.my frst guess would be to find the source of the smell
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Unread 05-29-2002, 08:28 PM   #3
johny1i
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Is it idling well/normal? I noticed from your signature that you have the mc2100 carb, so can we assume that all emissions junk has been removed? even the EGR? It's hard to answer this because there are so many possibilities, but a vacuum leak could have developed over the course of a few hundred miles due to rotten gaskets/hoses foing out now that you are driving it (it sounds like your CJ was sitting for a while by the way you worded the question). This would cause the engine to require more fuel (run richer and smell bad), plus your power and gas mileage would drop significantly. That's about all I can think of--
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Unread 05-29-2002, 09:59 PM   #4
Project CJ7
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My jeep had exactly the same problem... Most likely you got a valve that is sticking or burning up. Check the compression of each one of the cylinders do a wet and dry test. I'll bet thats what it is. I really wouldnt run it any until you do the compression test because I ran mine with those symptoms and I lost all compression in my 1st cylinder and its costin me $385 to fix.
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Just hit 62,000 miles
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Unread 05-30-2002, 01:18 AM   #5
Hippo393
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Location: Kent, Ohio
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Good suggestions here.
There's a great manual called the Jeep Bible, 2nd edition by Granville King and Willie Worthy. In it they discuss in-depth on maintaining a 200,000 mile engine, including noticing differences in mileage. All the troubleshooting you'd need is in there. A notable decrease in MPG is a major indicator of.....I'd go re-read the chapter myself for ya, but I'm too tired and lazy at this early hour... Really though, it'd do you (and any other CJ owner) well to own this manual--about $22 at Amazon or wherever!
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Unread 05-30-2002, 07:43 AM   #6
KG4PAM
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thanks for the suggestions! as for the gas smell, i dont believe it is in the lines, bcuz i checked them over and there are no wet spots. no johny1i, it is not de-emissioned. (except for the stuff that the previous owner removed, which i have to replace befrore july...) in my county/state it is legal to use an aftermarket carb, if the rest of the emissions stuff in the book is there. project cj7, i have tried to get it comp checked by two mechanics because i dont havve the gauge. they both said something to the effect of "Aw, i think its all right because it dont rattle when it starts up" of course, this was the same mechanic that said that he dosent use a tach to adjust idle spd, he does it by ear... maybe i should have him balance the tires on his head.. any suggestions/hints/rants and raves about swapping in a 4.0ho head? thanks again fo yalls help! jairus
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'81 CJ-7 Got it when I was 16!
'06 Hummer H3, boulder gray, Adventure Package(electric rear locker and 70:1 crawl ratio BONE STOCK)
'71 Kaiser-Jeep M35A2 Deuce and a Half cargo truck, with winch. <for sale>
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Unread 05-30-2002, 09:15 AM   #7
Project CJ7
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The guage is only like $20 at sears or autozone. Don't listen to that ******* mechanic...mine didn't rattle or anything, in fact it seemed to run fine except for gettin no gas mileage and the gas smell. Check it out for yourself $20 is a small price to pay to make sure of the problem.
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'86 CJ7 Project "Bulletproof"
2.5L 4-Banger
Just hit 62,000 miles
Custom Exhaust w/ Dynomax Muffler
31x10 Delta AT Tires
Bikini/Windjammer/Tonneu
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