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Old 05-18-2018, 06:38 PM   #1
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Default Low gas mileage/hestation 1990 truck

Hey y'all, I getting very bad gas mileage with my 90 pu, 13 mpg, used to be 22. It's has the KA24, 2wd, manual, 400,000 miles. Hesitation taking off from a stop, seems I have to be careful with the gas pedal and it slows down going uphill at highway speeds or into the wind.


I thought I had a sticking brake caliper, changed that. Changed the oxygen sensor, fuel and air filters. Ran two consecutive tanks of Gumout tune up in a can. Runs better, no change in gas mileage. Not many miles on plugs, wires, cap and rotor.

Last edited by bonzo; 05-18-2018 at 06:45 PM.
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Old 05-18-2018, 07:05 PM   #2
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Have you checked the timing? Should be set to 10 degrees btdc. If the timing chain has been done, the timing may have been set incorrectly.
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Old 05-18-2018, 09:07 PM   #3
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Cat converter plugged up? Or other exhaust (or intake) restriction?
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Old 05-19-2018, 03:39 AM   #4
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yeah and it just might be the fact that you almost have half a million miles on your motor lol (idk im no mechanic)
when was the last time you did a rebuild on this thing.
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Old 05-19-2018, 10:40 AM   #5
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I'd check the timing first, like Alabama pointed out.

If it's good, pull the codes to see if anything is amiss.

If the codes are good, get a compression test and a leak down test done. It could be that the rings are worn out and you are getting blow-by, but check the simple stuff before considering a worn out engine.
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Old 05-19-2018, 02:26 PM   #6
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yeah thats true
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Old 05-19-2018, 07:03 PM   #7
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Thanks, I'll try running the codes, I've never done that reckon this is good time to learn!

There hasn't been any engine work done.
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Old 05-19-2018, 07:38 PM   #8
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smells like a maf sensor to me......pull codes and see if it shows up
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Old 05-19-2018, 09:32 PM   #9
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So it showed 14 vehicle speed sensor, and 41 air temp sensor. Then I think I erased the codes by mistake. When I tried to doublecheck I got 55 normal operation. Took a test drive, checked again and normal...
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Old 05-20-2018, 12:33 AM   #10
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41 air temp sensor.

So, do you know where that is on your truck? Sometimes they go bad, but usually there is bad wiring to it or the little wire in the MAF is dirty. You can clean the MAF using MAF cleaner. It isn't expensive.

I bought this little package deal a few years ago, and I've used it 3 times since then to clean my MAF and throttle body area - and I still have plenty to do it more.

https://www.amazon.com/gp/product/B0091KCH6U

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