| Author | Message | ||
| Dirk Rabenschwanz (Dirk)
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Brian, can it be, that the extra flow makes that the O2 sensor doesnt reach his working temperature ? Thats what Steve mean. You know the O2 senor is mount directly on the cat and i think there is another temperature like in the bypass pipe. Thanks Dirk | ||
| Dirk Rabenschwanz (Dirk)
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Steve, i have a 3 wire O2 sensor. Yes, next step will be to check the sensor signal for cat and cat-less configuration. Thanks Dirk | ||
| Brian stewart (Eurocardoc)
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I would suspect that the extra exhaust flow without cat may be enough to affect the idle CO setting, you need to have someone check the exhaust mixture, probably should be 1.0% or so with the HC below 600ppm. It can be reset easily enough, be sure to reseal the hole for the adjuster before each reading. | ||
| Steve Magnusson (91tr)
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Dirk -- Do you know if you have a self-heated 3-wire oxygen (lambda) sensor or a 1-wire non-self-heated oxygen sensor? -- O2 sensors require a specific operating temp range to give the expected (non-linear) voltage vs air/fuel ratio behavior. Have you checked the O2 sensor voltage output while idling (warm) for both cat and cat-less configurations? | ||
| Frederick Thomas (Fred)
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P-car stands for Porsche. I am sure Brian just thought you were commenting on his intelligence on the subject.  | ||
| Dirk Rabenschwanz (Dirk)
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Sorry Brian, i have typed Your name wrong. Dirk | ||
| Dirk Rabenschwanz (Dirk)
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Brain, thanks, Do You have the correct values for setting up the injection system on my 84QV car? My car doesnt run with a cat bypass + O2 sensor. Rough running near idle speed. With cat in, everythings is ok. Do You have an idea ? What is a p-car ? Thanks Dirk | ||
| Brian stewart (Eurocardoc)
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The frquency valve can be discarded along with associated parts, and then reset the fuel system (you need a CO analyser). The fuel head is different I believe, I would have to look at the parts books. Anyhow the reason that the system is set up is to make the engine more efficiently, thus more power and (bonus) less emmissions. P-car owners are notorious for throwing away these things and they gain nothing. Also if the fuel burns less efficiently it will screw the cats. Just change the exhaust and reset the system, making sure that it is to spec. fuel pressure and base CO setting, the O2 sensor then adjusts the mixture to the proper value throughout the rev band. | ||
| Dirk Rabenschwanz (Dirk)
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Brian, is there any way to run a 84/85QV with lambda control like the 83QV without lambda control ? I asked, because i dont need any emission control. Do You have an idea ? Dirk | ||
| Brian stewart (Eurocardoc)
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The frequency valve in alongside of the fuel distribution head is controlled via an ECU located in the right rear fender, alongside are 1 or 2 relays, they typically fail, therefore no power to computer to adjust per the O2 sensor and the fuel runs very lean- won't burn and ends up in the cat, soon red glow, smoke, flames...... | ||
| Dirk Rabenschwanz (Dirk)
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Brian, You mean the frequency valve in the injection unit from newer QV cars ? Dirk | ||
| Brian stewart (Eurocardoc)
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Mainly fuel hoses going bad especially on carb. models, replace every one if you have a 308 and yes do include the vent lines tec.. 308QV and 328 are normally due to overheated cats. (back to the "slow down" light thread!) sometimes caused by the coil pack or the frequency valve power supply. | ||
| david handa (Davehanda)
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Appears common that the hose between the fuel filler neck and the tank can rot and split allowing fuel to spill. On www.tomyang.com, he talks of being present when his friend's 308 went up in flames from just this problem. I had my mechanic check my car at it's last service, and yup, it was rotted and cracked, though not quite leaking... | ||
| BretM (Bretm)
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I'd say the leading causes are electrical fires and cat induced fires. I read once that oil leaking (a Ferrari leak oil, never...) on the cats was the #1 cause of fires in them, how true that is I'm not sure, but it's definitely up there in causes. | ||
| joe saldana (Ironjoe)
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fuel tank location forced by the spare up front never a good idea in any car dist 3 inches from tank scary fuel lines too many to leak too close | ||
| Steve Magnusson (91tr)
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Mostly mis-maintance of the fuel supply systems (plus they usually do get pushed a little harder than your typical grocery-getter -- more likely that the exhaust manifolds are glowing). IMHO carb cars should probably have all (wet and dry) fuel hoses replaced every 5 years on the min side and every decade at the outside. The more modern high pressure lines on the injected cars are a little better longevity-wise, but still a 308i is ~2 decades old ya know. Unfortunately, there are a lot of high pressure connections on the injected cars, and not all simple banjo ones -- e.g., it needs some skill to just replace a fuel filter. | ||
| Dirk Rabenschwanz (Dirk)
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I found some pictures from burned up 308/328 in the last months. Is this a typical problem for these cars ? What cause these engine burning ? Dirk |