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Registered
Join Date: Jan 2003
Location: Australia
Posts: 96
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air fuel mixture problems - help sought
The hoses around the fuel injectors were looking quite old, so I had the injectors removed and cleaned and the surrounding hoses replaced. Car now starts better
 As part of the process I was told to have the exhaust gases analysed. I am not sure of the unit of measurement, but I saw the car put out about 15.4. The mechanic at the shop told me that the result is very good and shows the engine to be in good condition, as he said anything at or above 14.7 is a good result. I then spoke to my Porsche mechanic and he said that at 15.4 the air/fuel mixture will be too lean and that could damage the engine at high RPM. I asked him to adjust it, but he said on my car (it is a 1984, 4.7L, 4 speed automatic, sold new in Japan as a left hand drive model and is essentially the same as a US spec car, with around 75,000km or approx 47,000 miles, only run on premium fuel) the mixture cannot be adjusted after looking at it. They also said that the oxygen sensor (I have no cat by the way) should compensate where necessary. Another mechanic I know says thats not true and engine damage could occur at high RPM. I don't know who to believe and the last thing I want to do is damage the engine. What do you all think - could engine damage occur? How can I rectify this problem? Would having a cat put in help? Any advice/thoughts would be greatly appreciated. Thank you in advance.
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1986 951 Euro spec model Anthracite on black 105,000 km K&N, Lindsey Boost Enhancer, chipped, oversize fuel regulator 968 Club Sport anti sway bars Adjustable Koni Yellows Fuchs alloy : 9 inch rear, 7 inch front 2.5 inch stainless steel exhaust 1984 928 S2 (Jap spec) 1977 Mazda 323 - hard core tuned |
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12-25-2004, 05:38 AM
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Join Date: Feb 2001
Location: Viera FL
Posts: 5,642
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Ok, lets clarify a bit.
You have a Japanese model. Does it have an oxygen sensor? It will look like a "plug with a wire attached to it" somewhere on your exhaust BEFORE where the catalysts would be (somewhere in front of the first set of mufflers) An Air\Fuel ration of 15.4 is slightly lean. If you don't have an oxygen sensor system with lambda, it would not be hard to adjust the A\F ration to something slightly more rich. 14.7 is optimum for clean burn 13.0 is slightly rich - get a bit more power You make the adjustment for air\fuel mixture on the air flow sensor.which is that large aluminum funny shaped box with a cable attached to it UNDER your air filter housing. There should be an aluminum plug on the sensor which when removed (if it hasen't been removed already) that will allow you to adjust the mixture with a 6mm allen wrench. Clockwise = more rich anti-clockwise - more lean You will need a gas analyzer to set the mix accurately. PM me if you have questions or need more information AFJuvat
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Es geht nicht darum wie schnell man faehrt, sondern wie gut man schnell fahren kann. Ihr Brunnen der nutzlosen Porsche Information |
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01-03-2005, 08:34 PM
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Registered
Join Date: Jan 2003
Location: Australia
Posts: 96
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Yes I do have an oxygen sensor. The engine is very similar, if not identical, to US spec.
Thank you very much for your reply. I had a Porsche mechanic adjust it and then analyse the gases - it shouls now be right. THe only thing I found when he was done that the car was idlying very low - around 300rpm. I turned this up to about 500. Seems fine now.
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1986 951 Euro spec model Anthracite on black 105,000 km K&N, Lindsey Boost Enhancer, chipped, oversize fuel regulator 968 Club Sport anti sway bars Adjustable Koni Yellows Fuchs alloy : 9 inch rear, 7 inch front 2.5 inch stainless steel exhaust 1984 928 S2 (Jap spec) 1977 Mazda 323 - hard core tuned |
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01-05-2005, 01:16 AM
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