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 928 MPG help 
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Granny Driver

Joined: Thu Feb 02, 2012 10:03 am
Posts: 24
Location: Eagle, Idaho
Post Re: 928 MPG help
Ah got ya. Thanks Dano... the search continues.

_________________
1982 Porsche 928 "US" 4.5l Auto(soon to be 5spd) Black exterior , tan/brown interior
1986 Porsche 928S "US" 5.0l Auto Black exterior, Black interior


Sun Feb 12, 2012 2:29 pm
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Speed Limit Obeyer
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Joined: Thu Mar 17, 2011 7:37 pm
Posts: 71
Location: Van Nuys, CA
Post Re: 928 MPG help
Lets go over a couple of things:


Timing is stock? my car is at 20 degrees stock. I like mine at 23 degrees personally.

Double check ignition on each cylinder ? (try using a timing light on each wire and check for light)

What type of spark plugs do you have? How wide are the spark plugs gapped (assuming their not gapless)?

Temp sensor 2 (one that looks like a fuel injector in the water bridge) test the resistance, I believe cold is usually over 1000ohm and warm is under 100ohm if valid, otherwise its 45$ from 928intl as it is the primary controller of fuel mixture besides O2 sensor. Buy a crush ring with it. Might want to call it in because I dont know the size but they will.

WOT Sensor, Im not sure which pins to check for the circuit closing to the ljet connector but i think you can test it by disconnecting the leads at the spider. it should close the circuit only at 2/3 throttle.

Last thing I can think of is the l-jet brain itself is messed. you can try swapping with one from another 81-84 (80 is unique to itself). I dont see rebuilt ones for sell but you can talk to mark from 928intl or john speak from form jdsporsche (http://www.jdsporsche.com/). you might be in luck.


Theres not much else i can think of besides getting a wideband O2 sensor in to see whats going on with the AFR.


Hope this helps,
Jonathan.

_________________
Porsche 928S - 84 (Quartz Grey Metallic)
Automatic
Euro Intake manifold/Cams/Injectors, Headers
Left to do/fix: Sunroof,electric locks,some interior, paint body,replace hood lining, bad gas milage
A little of a fixer upper, but a labor of love!


Last edited by kelanel on Mon Feb 13, 2012 4:07 pm, edited 1 time in total.

Sun Feb 12, 2012 8:38 pm
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Speed Limit Obeyer
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Joined: Thu Mar 17, 2011 7:37 pm
Posts: 71
Location: Van Nuys, CA
Post Re: 928 MPG help
also forgot to mention, can you test with a mitty vac on your fuel regulation vacuum curcuit ( FPR's and dempeners all run off the same spot on the intake if i recall) to make sure they all hold vacuum and are not spurting fuel? a broke diaphram could be slurping fuel directly into the intake and causing this rich situation since vacuum only stops on throttle for FPR lines.

_________________
Porsche 928S - 84 (Quartz Grey Metallic)
Automatic
Euro Intake manifold/Cams/Injectors, Headers
Left to do/fix: Sunroof,electric locks,some interior, paint body,replace hood lining, bad gas milage
A little of a fixer upper, but a labor of love!


Last edited by kelanel on Tue Mar 20, 2012 10:22 am, edited 1 time in total.

Mon Feb 13, 2012 4:05 pm
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Webmaster
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Joined: Mon Jan 07, 2008 8:43 pm
Posts: 2078
Location: Sunny San Diego
Post Re: 928 MPG help
Hmm, maybe I need to also check this. This could be my bad mpg as well.

_________________
1981 Porsche 928 "Euro" 4.5 Litre Auto Gunsmoke Metallic Flat - Black Interrior
1983 Porsche 928S "US" 4.7 Litre Auto Light Bronze (Copper) Metallic - Brown Interior


Mon Feb 13, 2012 4:08 pm
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Granny Driver

Joined: Thu Feb 02, 2012 10:03 am
Posts: 24
Location: Eagle, Idaho
Post Re: 928 MPG help
Ok sweet. Thanks gents. I am headed to CA this weekend, so weekend after this one I will get on it!

_________________
1982 Porsche 928 "US" 4.5l Auto(soon to be 5spd) Black exterior , tan/brown interior
1986 Porsche 928S "US" 5.0l Auto Black exterior, Black interior


Tue Feb 14, 2012 6:53 am
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Speed Limit Obeyer
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Joined: Thu Mar 17, 2011 7:37 pm
Posts: 71
Location: Van Nuys, CA
Post Re: 928 MPG help
Hey leo. i just (hopefully) got a used J-let brain 81-84 incase you need to borrow one. its been tested good. let me know if you need it.

_________________
Porsche 928S - 84 (Quartz Grey Metallic)
Automatic
Euro Intake manifold/Cams/Injectors, Headers
Left to do/fix: Sunroof,electric locks,some interior, paint body,replace hood lining, bad gas milage
A little of a fixer upper, but a labor of love!


Fri Feb 17, 2012 12:16 pm
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Webmaster
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Joined: Mon Jan 07, 2008 8:43 pm
Posts: 2078
Location: Sunny San Diego
Post Re: 928 MPG help
kelanel wrote:
Hey leo. i just (hopefully) got a used J-let brain 81-84 incase you need to borrow one. its been tested good. let me know if you need it.


Thanks for offering that up. I'll let ya know!!

_________________
1981 Porsche 928 "Euro" 4.5 Litre Auto Gunsmoke Metallic Flat - Black Interrior
1983 Porsche 928S "US" 4.7 Litre Auto Light Bronze (Copper) Metallic - Brown Interior


Fri Feb 17, 2012 1:44 pm
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