924Board.org

[fergie]

I have narrowed down what could be causing my 924 to be running so poorly and decided it has to be the fuel system. From what i can tell it is running way too rich and fouling the spark plugs at lower rpms.

Today after cleaning the spark plugs with a torch i tried starting it up and running it somewhat hard to keep it warm so the plugs wouldnt foul out, and it ran really strong compared to usual (actually fired on all 4 cylinders apparently) as long as i kept the rpms up above 2500 or so.

When i let it sit and idle, it only runs on 2 cylinders. (removing the ignition wires from the #1 and #2 cylinders doesnt change the idle speed). when i pull out the spark plugs they are thick with carbon and the #1 cylinder plug was wet with gas yesterday...


Is there any kind of adjustment that would lean the mixture for all cylinders at all times? reading thru the haynes manual, there doesnt seem to be any such adjustment.

I am thinkign there could be a number of things wrong, including my cold start valve or fuel pressure control regulator malfuctioning... but most likely that my fuel distributor is just allowing too much pressure to the injectors... is the distributor adjustable at all?
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1996 Honda del Sol Si Turbo
1977.5 Porsche 924 (for sale)

[fergie]

Ok so i did some searching and found a post about tuning the CIS. apparently there is a 3mm hex key adjustment screw in the top of it.



if i try to tune the mixture with a wideband o2 sensor what air/fuel ratio should it show at idle?
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1996 Honda del Sol Si Turbo
1977.5 Porsche 924 (for sale)

[Smoothie]

Haynes pg. 100 under "40 Idle Adjustment" talks about setting the mixture. Somewhere in the 14.5:1 - 15:1 range should be good. Counterclockwise to lean, clockwise to enrich, and small movements of the adjuster make a big difference.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Mike924]

Hey, fergie,

Are you sure you've got the right grade of plug fitted? It could be that the plugs are running to cold...
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[fergie]

Ive considered that the plugs may be a problem as well. They are Autolite plugs i got from advance auto parts, i just told them the year/make/model of the car and they gave me the spark plugs for it so I figured they would be ok.

Would you happen to have a part # for the correct temperature of plug that i should be using?


btw- i also just found the little hole where you adjust the CO, and mine has no plug or anything in it.... so im guessing this vacuum leak hasnt been helping too much either.
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1996 Honda del Sol Si Turbo
1977.5 Porsche 924 (for sale)

[Ozzie]

This affects it slightly.
My plug is missing but the car runs ok.
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[FASTdan]

i havent noticed any difference since plugging that hole to be honest.
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1980 924LUX

[fergie]

Today i leaned out the mixture a bit (somewhere between 1/8 and 1/4 turn on the adjuster screw) and the car actually ran on all 4 cylinders for once because the spark plugs werent fouled out with gas. This made a huge difference in how it was running obviously... i was actually impressed with the acceleration. It was quicker than i expected.

So then after thoroughly warming it up i let it sit and idle so i could stick my wideband oxygen sensor in the tailpipe and fine tune it a little... because it now has twice as many cylinders firing, the idle speed was a little high so i went to turn down the adjustment on the throttle body a little. As i was doing this, gasoline starts spraying all over the place in the engine bay... so i run and turn the car off.

turns out my #1 and #2 cylinders injector banjo bolts started leaking real bad for no apparent reason. They have been leaking for a while but just a very slow leak that wasnt really noticeable, then all of a sudden they start spraying all over the place. I cant figure out why that would happen, but fortunately i ordered some new copper sealing rings yesterday and hopefully that will take care of the problem.

but yea for the first time i had it running really strong just before the gas spewed out.
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1996 Honda del Sol Si Turbo
1977.5 Porsche 924 (for sale)