88 gta 355 tpi Horrible mpg
05-24-2012, 07:56 PM
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Car: 1988 Gta trans am project 1-1/2
Engine: 86 4 bolt main cammed sbc 355 hsr
Transmission: 89 wc bw t5
Axle/Gears: Bw 9 bolt (3.27) pbr 11in
88 gta 355 tpi Horrible mpg
Ok so i have a 355 tpi no check engine light comes on when the motor is running. Another thing to is i have a high idle running around 1000-1100rpm at idlewhen i put it in drive it idles/runs around 500-700rpm at a stop so thats somewhat right what could cause horrible mpg so far i changed out fuel filter, spark plugs, accel wires, an cap an rotor also do have a cam 208 intake, 218 exhaust with a 407 lift the heads on the 355 are gm cast iron 194 intake opened up to 202. I am running egr an cold start do these play a major role in mpg ????
05-25-2012, 12:44 PM
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Car: 1988 Gta trans am project 1-1/2
Engine: 86 4 bolt main cammed sbc 355 hsr
Transmission: 89 wc bw t5
Axle/Gears: Bw 9 bolt (3.27) pbr 11in
Re: 88 gta 355 tpi Horrible mpg
70 miles to a full tank
05-25-2012, 01:08 PM
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05-25-2012, 03:44 PM
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Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: 88 gta 355 tpi Horrible mpg
Holy crap thats not even close to right...
05-25-2012, 06:04 PM
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Car: 85 Trans Am
Engine: 98 Vortec 350 LT1 Cam w/ TPI
Transmission: T56
Axle/Gears: 9 bolt 3:27
Re: 88 gta 355 tpi Horrible mpg
Could be a bunch of different things. Leaking 9th injector, stuck FPR, leaking FPR diaphram, Leaking injectors... That's all I can think of right now. What do the plugs look like?
05-25-2012, 06:52 PM
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Car: 1988 Gta trans am project 1-1/2
Engine: 86 4 bolt main cammed sbc 355 hsr
Transmission: 89 wc bw t5
Axle/Gears: Bw 9 bolt (3.27) pbr 11in
Re: 88 gta 355 tpi Horrible mpg
Yeai know its terrible what are causes you guys think it could be ??? I was thinking i got a vac leak someone just havent tested to see yet i know tpi motors are known for the runners an the corners of base intake gaskets let go But the funny thing is i have no engine light coming on all injectors read 16.7 ohms. An fuel pressure holds a solid 42 at idle an jumps to 47 when under load all of the emission stuff has been ripped out expect egr an solenoid all vac lines are good no cracks or breaks
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05-25-2012, 06:58 PM
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Car: 85 Trans Am
Engine: 98 Vortec 350 LT1 Cam w/ TPI
Transmission: T56
Axle/Gears: 9 bolt 3:27
Re: 88 gta 355 tpi Horrible mpg
Fuel pressure sounds a bit high. Should be 43 at idle with vacuum unplugged and around 35psi with vacuum plugged in. Basically the max pressure you should ever see out of it is 43PSI.
05-26-2012, 08:20 PM
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Car: 1988 Gta trans am project 1-1/2
Engine: 86 4 bolt main cammed sbc 355 hsr
Transmission: 89 wc bw t5
Axle/Gears: Bw 9 bolt (3.27) pbr 11in
Re: 88 gta 355 tpi Horrible mpg
Ok so i tryed a different fuel pressure guage an it reads 40 psi at start up an it runs jumps to 43 when under a load. I also did the whole fpr test with the vac line off an no gas came out of the line so it tells me that it is good i have no idea what i could be im very stumped
05-27-2012, 08:34 PM
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05-27-2012, 10:25 PM
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Car: 83 POS monte carlo 2015 chevy P/U
Engine: 92 5.7 tpi 5.3
Transmission: 700r4 6L60E
Axle/Gears: 2.42 too high
Re: 88 gta 355 tpi Horrible mpg
does the check engine light work right? without cranking the motor, turn
the key on, does the CEL flash on & off then come back on?
have you tried to pull codes?
no doubt something is bad wrong.
tuning the computer would help, but the cam isn't that big.
if the basics aren't right, tuning alone won't solve the problem.
the key on, does the CEL flash on & off then come back on?
have you tried to pull codes?
no doubt something is bad wrong.
tuning the computer would help, but the cam isn't that big.
if the basics aren't right, tuning alone won't solve the problem.
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