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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 928 MPG help
Hey gents,

(i posted this on Pelican Parts a while back... still having the issue)

I am a 928 junky. Through the years my dad has had quite a few... 89 S4, 87 S4, 1980, and now my old 86S. I have a few as well... an 82 S with 105k, a 1980 5 spd and a 79 no sunroof car.

The 82 has been sitting under cover for about 10 yrs just awaiting resurrection which I am in the process of doing now. The car is primo with a few exceptions and only has 106,000 on it.

The last two tanks I have gotten about 10 mpg(or less) on and anytime you step on it there is a huge cloud of unburnt fuel that spews out the back. I have run some Lucas through it as well as replaced the injector seals(some of them were leaking) and had the injectors tested while I had them out. They tested out great. I also replaced all the vacuum lines while I was in there most of which shattered into a million pieces as soon as I touched them. I have swapped MAF's just to see if it was bad but still having the same issues. I have changed out the cold start injector, and just installed a new 02 sensor.....Before I go testing all the sensors or just randomly replacing stuff, is there anything that springs to mind in any of you that might be the issue, or has anyone had the same issues?

Thanks for your time.

Ramon

_________________
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 07, 2012 12:21 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
Also forgot to add, I purchased a new "green wire", check the vacuum advance unit in the dizzy, and it is fine as well.

Here is another question. someone suggested that is the fuel pump was getting to much current that it would be over fueling. Wouldnt the fuel pressure regulators, fix that issue? I also tested the regulators and made sure my return line wasnt clogged and flowing freely back to the tank.

Thanks

_________________
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 07, 2012 12:28 pm
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Joined: Mon Jan 07, 2008 8:43 pm
Posts: 2078
Location: Sunny San Diego
Post Re: 928 MPG help
I too am kinda fighting this with my 83. My 81 Euro CIS get's better mileage, so I too am confused. It looks like you've replaced and checked everything I would have checked or replaced as well. I am wondering if a clogged Cat would affect as well? I stated to also think of the L-Jet, I wonder how much that would cost to have tested? I'm with you on this one.

_________________
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


Tue Feb 07, 2012 12:32 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
I have built a Y pipe and completely gotten rid of the cats, because I was thinking the same thing. Although it was a night and day difference power wise... it made no difference on the MPG front. I have it on jack stands now because I am yanking out the broken shifter cable(what a PITA) and building a new exhaust Y pipe back. So i may just drop the tank and flush it for shits and giggles. I will keep you updated on the progress maybe it will help you on your issues. The cats are good if you are in need of one.

Thanks

_________________
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 07, 2012 12:53 pm
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Speed Limit Obeyer
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Joined: Tue May 26, 2009 11:33 pm
Posts: 88
Location: Edmonton AB
Post Re: 928 MPG help
Hey Ramon,this may be silly but if you have checked out all those other issues yet still have unburnt fuel,what is the condition of your distributor cap,rotor,plug wires and plugs?If those are not proper it could explain why the fuel is not being burned properly.
PS Check your air filter as well

Just my two cents

Kurt


Tue Feb 07, 2012 6:10 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
KDOG. Thanks for the reply. The cap, rotor, plugs, and air filter are brand new. The only thing I haven't changed in that list are the plug wires. They seem to be in very good condition and it tested the conductivity with an OHM meter and hey all seem to read about the same so I know there aren't any breaks in them.

Thanks again. I am open to any and all suggestions, besides cleansing the demons with fire. I'm kind of partial to the old girl. :-)

_________________
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 07, 2012 6:32 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
Here is a thought I just had.... Could my WUR be bad and think the engine is constantly cold? Therefore always be running in the rich warm up mode causing my excessive fuel consumption?

Ramon

_________________
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


Sat Feb 11, 2012 10:50 pm
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Joined: Mon Jan 07, 2008 8:43 pm
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Location: Sunny San Diego
Post Re: 928 MPG help
Hey Ramon, Put your Mode; Year in your Signature. It helps. I didn't know you are referencing a CIS car.

_________________
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


Sun Feb 12, 2012 7:43 am
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Granny Driver

Joined: Thu Feb 02, 2012 10:03 am
Posts: 24
Location: Eagle, Idaho
Post Re: 928 MPG help
Sorry its the 82 US car.

_________________
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 9:08 am
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Joined: Mon Jan 07, 2008 8:43 pm
Posts: 2078
Location: Sunny San Diego
Post Re: 928 MPG help
spooledx2 wrote:
Sorry its the 82 US car.


An 82 US should be L-Jet, so no WUR.

_________________
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


Sun Feb 12, 2012 10:22 am
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