For awhile now has been getting pretty low fuel milage

Tiny
STEVE19791
  • MEMBER
  • 2000 MITSUBISHI MIRAGE
  • 145,000 MILES
No dtc at all and ran great until recently has started to have a rough idle have done numerous things to try to bring mileage back up to where it once was. Did find one of the coils were bad and replaced it but still no change. Kind of wondering if it damaged cat because down stream 02 don't really look right which are both new. Fuel trim long around 3 or 4 + Scanner shows egr/vvt inconclusive just recently which has lead me to that. Before this began it got around 30 to 33 mpg in town and dropped to like 17 only get around 120 to 180 to ten gal or more. Driving me batty have done just about everything possible to try to solve it. Any suggestions
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Friday, September 27th, 2013 AT 7:49 PM

3 Replies

Tiny
HMAC300
  • EXPERT
Check fuel pressure with a gauge at fuel rail shold be 38psi w/vacuum 47-50 w/o at idle.
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Saturday, September 28th, 2013 AT 5:57 AM
Tiny
STEVE19791
  • MEMBER
Fuel pressure checked out good. Have noticed a new clue. Scanner connected drive cycle monitor was showing egr/vvt inconclusive think that test is being canceled because of a issue I have just discovered. While driving when I let off accelerator for a few seconds it goes out of closed loop. Into open and back into closed loop at idle when raised say 2000 rpm and released does same thing so I believe is cancelling egr mon test. During this quest at one point when I let off accelerator going down hill would down shift up shift as if was changing in and out of overdrive so I suspected throttle position sensor first I put another one on it from a parts car I have and still no change then I put original one back on and no change light finally came on said tps open condition below threshold realized adjustment was below threshold adjusted to specification the light stayed off the up and down shifting stopped but poor fuel econ persisted egr still inc and as stated before still dropping out of closed loop on deceleration both o2 have been replaced. Have cleaned intake and completely flushed egr passages both directions ect does have a slight stumble at idle Maybe this will help draw a picture of the issues I am scratching my head about. Thanks for your time
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Thursday, October 10th, 2013 AT 10:59 PM
Tiny
HMAC300
  • EXPERT
Have a pro hook his scanner u sp so he can test the egr system separately. It may be a plugged egeror the valve is screwed up. I have no further suggestions
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Friday, October 11th, 2013 AT 5:42 AM

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