14 mpg wtf???
07-16-10, 10:01 AM
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14 mpg wtf???
93 SC300 200,000 miles. No CEL.
So far Ive done spark plugs, wires, cap, rotor, cleaned out the Throttle body, Seafoam through oil, gas tank, brake booster, and changed the fuel filter. I sprayed around for vacuum leaks but havent found any. Air filter is still white.
All that and the car still gets 14mpg. I only floor it when I get onto the freeway. Anything else Im missing? Can a O2 sensor go bad without a check engine light?
Ive searched through many threads similar to mine with no real leads to whats causing the bad mileage.
Car idles @ 1250-1500 in Park and 1000 in Drive
So far Ive done spark plugs, wires, cap, rotor, cleaned out the Throttle body, Seafoam through oil, gas tank, brake booster, and changed the fuel filter. I sprayed around for vacuum leaks but havent found any. Air filter is still white.
All that and the car still gets 14mpg. I only floor it when I get onto the freeway. Anything else Im missing? Can a O2 sensor go bad without a check engine light?
Ive searched through many threads similar to mine with no real leads to whats causing the bad mileage.
Car idles @ 1250-1500 in Park and 1000 in Drive
07-16-10, 01:07 PM
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Damn. I kind of think my ecu is busted. Before I did my tune up it was running very rough. I think it wasnt firing in one of the cyl. The car never threw a cel when even though I knew the car was misfiring. Is there anyway to lower the idle?
07-16-10, 01:37 PM
#5
If you have a high idle, you may have a vacuum leak somewhere that the ecu's trying to compensate for by dumping gas...Bad O2 sensors will kill your fuel mileage as well....You should start with that and see how she does.
07-16-10, 08:25 PM
#7
You Should do a compression test. I have a 92 5 speed SC300. Car ran fine under normal load, but you couldn't smash in it. It also got 15 MPG on a good day, bad day, Up hill, down hill, tail wind... No one could figure it out, checked my brand new plugs, they looked like poo. So I did a compression test while they were out, turns out I had 2 cylinders only making 45PSI... No check engine light. No sensors showing signs of a Bad Engine.
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07-17-10, 03:24 PM
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You Should do a compression test. I have a 92 5 speed SC300. Car ran fine under normal load, but you couldn't smash in it. It also got 15 MPG on a good day, bad day, Up hill, down hill, tail wind... No one could figure it out, checked my brand new plugs, they looked like poo. So I did a compression test while they were out, turns out I had 2 cylinders only making 45PSI... No check engine light. No sensors showing signs of a Bad Engine.
Car seems to accelerate well. Was your car sluggish? Is a compression test hard to do. Ill be doing a search.
Last edited by turbopwr; 07-17-10 at 03:28 PM.
07-25-10, 06:05 PM
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Dude I get about the same in my 93 sc300 5spd in the city and about 20mpg on the highway. I also just changed out my sparkplugs and wires. I dont know how people here get 20+ mpg.
07-25-10, 06:44 PM
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My 97 SC300 averaged 22mpg and got as high as 28mpg on the highway on long trips.
Try to figure out the idle issue, its supposed to be 600-800. My SC only idled that high on a cold start but went down after it was warm so maybe you have a temp sensor thats not telling the ECU that its warmed up??
Try to figure out the idle issue, its supposed to be 600-800. My SC only idled that high on a cold start but went down after it was warm so maybe you have a temp sensor thats not telling the ECU that its warmed up??