i realise that this is for mercedes only but a friend of mine has a volvo 1986 760GLE and the engine has become very rough and the exhaust gets red hot just after the exhaust manifold.
there is no turbo.
could it be a fuel problem?
or the catylictic converter??
there is no black smoke or evidence of an over rich fuel mixture....unless the catalyctic converter is working very efficiently??????

Whoa, the exhaust is obstructed. I think the Volvo might have a cat or precat in the downpipe. If so that's the problem. I can't imagine any other situation producing a visible glow in the exhaust system..

That does sound like a plugged Cat. If the pipes are glowing that bright, I'd be worried about spontaneous combustion in the surrounding areas, to include combustibles in the passenger compartment.

In my opinion, the raw fuel was burning inside the manifold. The air pump is injecting fresh air into that part of the exhaust pipe to burn the raw fuel in order to clean the smog. The car may be running a little too rich or too lean.

David



[Edited by be459 on 12-04-2000 at 11:57 PM]

That is a lean condition.

I once experienced exactly the same condition on my 16V. The engine started running very rough. I lost power. I thought the engine was gone. I lifted to hood only to see a my pre-cats glowing red hot. The problem? One cylinder was not firing due to a fouled spark plug. I suppose this approximates the lean condition with extra fuel being burned near/in the pre-cats. Replacement sparkplug cured all symptoms.

John

Get it fixed asap. This *exact* problem occurred with a friend's Volvo and two hours after we were looking at it and scratching our heads the car caught fire and burned completely on the way home. He got out ok but had a pretty wild story to tell about flames erupting from under the hood (and all the way out the back) at 60mph. As nothing but a block and some twisted metal was left we never did figure out what was wrong but the posts above appear to make sense.
Matt
By the way - it was a 760GLe and was somewhere between 84-88...

thanks to all for your input.
i guess we will start with the spark plugs