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81 500SLC Vacuum leak
All, I've been driving my 81 500SLC and it's running a little rough. I suspect and have long suspected a vacuum leak but have not had any luck finding it.
The economy gauge is usually in the center at idle and the car runs rough when idling. When cold, the car is hard to start and cuts out when you depress the gas until it warms up. When warm, it still runs rough at idle but better then when at cold On the road, it has good power. I've tried spray carb cleaner around the engine to determine if there is a vacuum leak in the engine bay but I have not found anything. The central locking does not work but this usually does not create these rough running problems, at least not in any other MB that I've owned. I don't have access to a smoke machine so i'm wondering if anyone can suggest common areas for me to look. Many thanks
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With best regards Al |
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Al,
Like I said weeks ago, you'll need to verify engine vacuum using an actual vacuum gauge on the manifold. If the vacuum is really low, then start trying to use old school vacuum gauge troubleshooting (see what the gauge does when the throttle is opened). If it's just a vacuum leak, you'll need to start disconnecting and plugging off vacuum connections one by one while still using the vacuum gauge (not the economy gauge). It's possible to have something like a brake booster cause a problem. Otherwise if the engine vacuum is low but not due to a leak, then something else is causing the problem, usually in the engine itself. Ignition timing can be at fault, but the engine normally will lack power and economy due to retarded timing. Valve timing can also be at fault, but again will show up as hard starting and a lack of power. Low engine compression will cause low vacuum but with excessive blowby, exhaust smoke, and oil consumption. Valves not sealing are another potential problem but will be related to that specific cylinder. One last possible cause of low vacuum is a restricted exhaust system (lack of power again).
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Erich Loepke 2010 Ford Focus Currently Benz-less |
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Erich,
Yes you did, and I bought a vac gauge and then completely forgot! I think that there are a number of things going on here. Contaminated gas and rust in the tank is probably the main factor along with FD issues and a vac leak . I drove it to work today and it was mostly ok. On the drive home, it started to act out and died a couple of times. I managed to limp to a gas station and stick 12 gallons of premium which got me home without any further break down.
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With best regards Al |
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