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#1
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Gas milage issues, now I'm stuck.
All questions pertain to a 1992 USDM SVX.
My SVX has never gotten very good milage - at one point I was lucky to see 10 mpg In an attempt to fix this problem, I have replaced my 02 sensors, and replaced all vacuum lines and EGR related tubing under the intake plenum with new material. This has helped in a moderate way, I now see 18mpg on the Hwy, and about 12 in town. I drive with a moderately heavy foot. Could someone assist me in next steps in my diagnosis of this problem? Knock sensors, maf cleaning? There is no other indication of problems - drivability is excellent, and there is no CEL illumination. Thanks, Patrick
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Patrick 1995 Ebony Pearl. S.N. 0001 "Araby" JDM Power Mode Switch, Integrated GPS/Video Player 6Xk Miles. 1992 Teal - Sold to Mysvxrocks [SIGPIC][/SIGPIC] |
#2
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Knock sensors. I'm wondering if your ECU is retarding the timing so much that it's affecting your gas mileage. I can get 18 around town and I'm a 19 yo with a lead foot.
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-Jason (8/23/07-Present) 1995 Subaru SVX LSi (197k) Polo Green (#1102) 03/95 Mods: DDM Tuning 4500k 35w Low Beam HID, 100w H3 Bulbs, Extra Ground Cables, 15 minute $12.96 mod, svxfiles designed transmission mount (), sporting a "new" tail light bar, silver BBS rims, custom power steering cooler (one that doesn't dump ATF constantly), new negative lead cable, no more third or fourth gear (1977-Present) 1977 Chevrolet Corvette (81k) Silver (12/01/2011-Present) 2005 Subaru Outback 2.5i Limited 5MT (97k) I have a bad feeling about this. -Obi Wan Kenobi |
#3
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change fuel filter
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Seth 94' Barcelona Red w/ Tricoat black 2-tone AWD Ls -Sold Mods:AWD conversion/4.44 swap by Budfreak, Custom red interior lights, Custom Satin black dash, Power mode switch, Cold air intake, Permecool tranny filter,Sony xplode 10" sub, Sony xplode 1000w amp, Blitz in-line driver, DDM Tuning 6000k HID's, New paint job/body work by me, 97' Grill, QC shift kit, 17'' MB Motoring rims, 15&20 min mod, front & rear urethane swaybar bushings, Custom fiberglass sub box, Custom red led a/c control unit, perrin lightweight crank pulley, Black wrinkle finish powdercoated intake manifold w/ clear hoses , 02' outback heated/power black leather seats Soon to come:Fiberglass hood, upholster ALL suede to black leather Past subies: 92' Pearl White/black top LS-L-SOLD 96' Legacy Outback-TOTALED 99' Legacy Outback Limited 30th anniversary edition-TOTALED 98' Forester L -Totaled Other toys: 99' Forester S -WRX brake upgrade, soon an 04 wrx motor swap 06' B9 Tribeca-Stock 1982' Yamaha xj650 Maxim Mods: work in progress |
#4
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clogged cats...
dirty air filter.... old spark plugs... tires not at the right pressure.... out of alignment.... have you checked for any codes stored in the ECU? That's probably the best place to start before you go replacing anything else. -Bill
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Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
#5
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I've heard of first gen legacies getting crap mileage due to a faulty knock sensor, so it probably applies to SVXes as well.. I'd suggest getting the new style knock sensors that have the connector right on the sensor off of a newer EJ motor, along with the enough of the mating connector and wiring to wire them into your car, they should be interchangeable but I've never tried...
Although I think checking your tire pressure (I have mine at 34 PSI F/R) and replacing your plugs (NGK V power) and fuel filter (OEM or good quality aftermarket, NOT Fram) would be where I'd start since those are easier than the knock sensors. I'm not sure how to test the knock sensors aside from hooking up a timing light and tapping on the block around the sensor with a screwdriver handle and see if the timing retards (Depends on if the ECU is smart enough to ignore knocks that aren't in time with the coils firing, it's old enough that it probably isn't, but it's advanced enough in other areas that it might be) You can use a timing light to check the timing, but if it's off it's not adjustable, if it's off it means there is a problem (like faulty knock sensors), but I am not sure how to do it on an SVX, nor what the timing it supposed to be... I can look in the factory service manual tomorrow and let you know.
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1992 SVX LS-L #1222 Pearl White 1987 GL Turbo wagon, 5 lug conversion, D/R 5 speed (Rice killer) 1992 Dodge Ram 4x4 diesel (car hauler) 1968 Dodge Polara convertible (Camaro killer) 1990 Toyota Corolla FWD auto (330,000 mile grocery getter) 1986 VW Jetta |
#6
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Quote:
Wow, you did improve a lot of mpg...good luck.
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-SSSVX 92 LS-L TEAL since Aug '01 92 LS-L YELLOW since Mar '05 |
#7
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+1 i got 28 on the freeway, and 22 around town in my 92, somthing is definatly wrong, do you have a cel?
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1991 xt6 eg33? 1993 gc track car |
#8
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Nope, no CEL.
Well, all of this stuff is good maininence anyway, I'll just go ahead and replace the cats, I was driving around for so long at such a rich AF that I'm sure they are in need of replacement anyway. Same with the plugs, air filter, fuel filter, knock sensors, and alignment. I'll get em changed out today, and we'll see how she looks. -Patrick
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Patrick 1995 Ebony Pearl. S.N. 0001 "Araby" JDM Power Mode Switch, Integrated GPS/Video Player 6Xk Miles. 1992 Teal - Sold to Mysvxrocks [SIGPIC][/SIGPIC] |
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