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Discussion Starter · #1 ·
I have 92 10 extended cab automatic with the 2.5l and i am only getting about 15 miles to the gallon. I have put it on the scanner with no codes showing up. It runs great and the timing is spot on. just cant figure out why its sucking more gas than my v8 truck does. Ant help would be appreciated.
 

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Check the Exhaust manifold (in the area of the welds under the heat riser tin) for cracks. Check the O2 sensor. Check the CTS. Plugs/ cap/ rotor new/Good?
 

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My bird had terrible mileage when I first got it, like 11mpg, I changed the MAP and the o2 and air filter and it tripled the mileage.
 

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Discussion Starter · #4 ·
There are not any cracks in the exhaust manifold, you can see where its already been repaired. Would the check engine light came on if i had a bad 02 sensor or map sensor?
 

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Mine still pops on and off, I checked it once and it was some weird code for something the car doesnt have and the book said to ignore it. You can have a bad sensor and not have the computer throw a code. If the o2 is over 2 years old I would replace it and if the map is getting on in years I would replace it too and check your air filter(switch to a KN or something you only have to buy once).
 

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my check engine light comes on for about 3 seconds at start up but thats it
 

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On these older OBD1 systems the sensors almost have to completely fail for a CEL, so out of tolerance is toleratable by the oe brainbox.....
 

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Cool, Tight, & STRONG....
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On these older OBD1 systems the sensors almost have to completely fail for a CEL, so out of tolerance is tolerable by the oe brainbox.....
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les--

I agree 100%...

One of the "things" that you learn pretty quickly about these rigs are the things that DO NOT turn on the Service Engine Soon light, and still it runs like crap/gets bad gas mileage.

I would be willing to bet that the original poster, travisff, STILL has an exhaust leak, the tip off being that he stated that the OE exhaust manifold had already been welded up (fixed) before. This says that the manifold is already brittle and the leak may not even be visible, it doesn't take much to screw up the O2 sensor. (this issue is why I like the idea of the aftermarket cast iron exhaust manifold).. A very small leak will throw the O2 sensor full lean and enriches the mix way up.

And, on this point, the "Caveman" is 100% right, he says the O2 sensor has no replacement schedule. It "should" last, but in actual practice they get slower and do become fouled. For the small co$t of a new replacement, after travisff gets things ironed out, maybe a new O2 sensor would be a wise investment.
 

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Discussion Starter · #10 ·
I had another exhaust manifold and checked it for cracks today. I found one small one and fixed it. (Still not sure if the one on the truck is cracked or not but this way i will be sure that it has a good one) Gonna change it out on sunday along with the new 02 sensor. Hopefully this will cure my problem. As for the tank leaking i am pretty sure its not. I have let it sit for a couple of weeks and no change on the fuel gauge but if i drive it to work and back (about 50 miles round trip) it uses a quarter of a tank of fuel. And I have the 20 gal tank. Any other suggestions besides the exhaust manifold and 02 sensor?
 

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I didn't notice it on the gage either but was getting best of 17mpg. Mostly highway but not every day. It was just a thought, if it's dry no worries, bout that anyway.
 

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Does the Cat glow or the Exh manifold glow after a nice drive at night?
 

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Discussion Starter · #13 ·
nope, the cat is clear. took it off and looked at it and it still looks good. I am in need of a vacuum diagram. I think all my vacuum lines are misplaced. I looked at my egr valve last night and the line going to it was not even pulling a vacuum. If anyone has one it would be great.
 

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Autozone has vacume diagrams.

The EGR WONT have vacume on it untill you are going down the highway and the ECM commands it on.......

Also as per the last question posted..... If the Exhaust manifold glows red then you are running lean, if the cat glows, you are running rich........
 
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