Mercedes 300E 2.6L Engine Problems.

I own a 1990 Mercedes 300E 2.6L that has a problem my local mechanic cannot resolve.
The car sputters when accelerating, and almost dies. I changed the plugs, wires, rotor, cap, but it still occurs.
Inaddition, recently I was drive over a bridge, approximately 7 miles from home, when the car started to sputter. I decided to keep driving (it would only go 2-5 mph) to get to the other side. I was pulled over by a policeman who stated that it seemed that the car was on fire. The entire exhaust manifold was glowing. The car was parked to let the exhaust cool.
Any ideas on what could be wrong with the car?
Thanks in advance. Pierre
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Since the policeman thought that the car was on fire I'm guessing that something was letting of a red glow under the car (since you mentioned the exhaust manifold). If this is the case then you might want to see if the catalytic converter has melted down. If it has, then you'll also want to find the cause of this meltdown before investing in a new one.
Josh
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Exhaust manifold glowing means too much fuel that your cat was ecploding fuel... clogged by now... This means you probably got bad fuel distributor... check plugs... there probably is several fouled out plugs.
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I believe your motor is either fuel starved and running too lean or the ignition timing is way out of specification.
The most fuel is used during acceleration and long hill climbing so fuel starvation would then show itself.
Fuel starvation could be due to a dirty and clogged fuel filter. When was it last replaced?
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The first time I read your post I thought too much fuel was causing the glowing exhaust. But the the sputtering as you describe it led me to the fuel starvation theory.
Does the exhaust smoke black? Does it reek of unburned fuel? If so, the motor is being over fueled. If not, I stick to the fuel starvation theory which causes misfiring and that unburned / partially combusted mixture is burning inside the exhaust and so causing the exhaust to overheat.
Another thought is that the catalytic converter has disintegrated and the exhaust itself is obstructed and that's causing the motor to stumble on any occasion where you demand some power.
I repeat, check the fuel filter to ensure the motor is adequately fueled, if only to rule out the fuel starvation possibility.
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Thanks for your input. I started the car today and it seemed ok. The exhaust smoke was not black. I have an appointment to visit a new mechanic on Saturday. I will use the information I received from yourself and others to attempt to get to the bottom of this issue. As for the fuel filter, I believe that the it might not have been changed. I am not sure of person I took my car to before changed the filter but I'm assuming that he didn't.
I will take a look at all that was mentioned and update you of my findings.
Thanks again for your assistance.

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Tom is right.
Too lean mixture will overheat the catalytic converter.
I had a similar problem with my 1991 300SEL (W140, 104 engine). My problem was a defective air mass sensor, but anything causing too lean mixture would cause the a similar problem.
In my case, the symptoms were exactly as you desribe. The overheating caused the catalytic converter to burn out, clogging the rest of the exhaust system. So the engine had two problems: Lean mixture and clogged exhaust. Before clogging the exhaust, it would run reasonable when cold (due to richer mixture) but with limited power when hot. With clogged exhaust it was almost no power.
Be careful. A burned catalytic converter (probably already happende according to the policeman) is expensive.
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too much raw gas is being injected and being burn in the castlic converter.. more than likely it is a fuel injector problem

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