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Worse gas mileage after tune up

754 Views 22 Replies 11 Participants Last post by  sixsix
2001 V6 4.3 with body lift and oversize tires. 198,000. Ive always got around 16 mpg up to 192,000, then it dropped to 14 mpg.
One day it wouldn't start, turned over but wouldn't start. Moisture was getting in the cap and rotor during extreme fog conditions.( I've changed these several times over the last year, and still not 100 pct sure I've fixed that problem. Won't know till the next fog). Anyhow, when it wouldn't start I also changed plug wires, PCV valve, and replaced the plugs with iridium. I also replaced the fuel filter and air filter. The old plugs were horrible, so I expected my mileage to return to 16 mpg, or at least remain at 14, but instead it dropped to 12mpg.
(As a side note, my mileage dropped to 14 mpg when I got new tires installed, may be a coincidence, not sure). My tester reads no codes.
I have two questions, is it possible that installing iridium has actually made my gas mileage worse? Also, is it possible that IF my actual distributor is bad, it could be making the mileage worse? (If I get moisture in my rotor and cap again, my next step is to replace the actual distributor).
* Heads up, Im not a mechanic, I'm a 61 year old little lady who doesn't have the money to pay a mechanic to do this, so I'm learning about and doing lot more than I ever thought I would, or care to. I can now take the dog house off in 10 minutes, and put it all back in 30. I never wanted to get skilled at that. So with that in mind, please don't get too technical with your explanations, I'm not an idiot, but I'm not a mechanic either. šŸ˜ Many thanks for your input.
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could be a vacuum leak if the work you did disturbed any vacuum hoses in the engine bay.
maybe one of the new spark plugs wasnt fully tightened and so that cylinder is leaking some compression.
are all the new tires filled to the proper air pressure?

I second the advice on taking the doghouse off and having a look around. they are really easy to zip off once you know where the hardware is.
tricky to get back on without cracking the kick plate next to the gas pedal in half, watch for that. and its easier to line up the upper bolts for the doghouse from the engine bay side.

my van has 200k miles and gets about 20 mpg at 60 mph on flat ground. around 14 mpg in town. I drive like a.. well nevermind. I drive slowly ;)

just a few ideas
Mitch
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