So first let me point out that I have searched for both of these problems all day to no avail, most likely due to a million different causes, but please bear with me and toss in your two cents if you have any ideas. The car is a 1990 300SE.
First problem is with the heat. It works fine at idle/low RPMS, but accelerating or revving the engine makes it go cold. If the car is idled up to full operating temperature prior to driving, this problem does not happen. If you start it and then drive soon thereafter, you only get heat at idle. I cleaned and tested the monovalve and it seems to be fine, and I know it is clean and clear. WTF?
Second problem is with performance when the engine is at temperature. The car starts smoothly when cold and drives as it should - drives great actually. New EHA seals, fuel filter, plugs, valve cover gasket, injectors with seals, resealed fuel distributor, replaced cat with straight pipe, new OVP relay, new MAS, and several other recent maintenance items. When the car gets warmed up however, it will stumble and misfire off the line. It will barely accelerate at any degree of pedal pressure and will stumble harder the more you press the gas. Once rolling up past about 10mph the car again drives fine. The workaround I have figured out is to hold the gas down a bit with my foot on the brake at lights or stop signs, or while in traffic - as if about to do a brake stand. If I hold it at 1100rpms for about three seconds, it idles smoothly again and will take off from the stop smoothly. The car will start hot, but requires a bit more cranking. If you crank until it seems to fire up it will go up to idle and then die immediately - holding the key in the start position for about two or three seconds will keep it at idle and it will stay idling smoothly. The car always idles smoothly regardless of engine temperature. Big WTF.
Any help or ideas would be very sincerely appreciated. Both problems are getting severely annoying.
First problem is with the heat. It works fine at idle/low RPMS, but accelerating or revving the engine makes it go cold. If the car is idled up to full operating temperature prior to driving, this problem does not happen. If you start it and then drive soon thereafter, you only get heat at idle. I cleaned and tested the monovalve and it seems to be fine, and I know it is clean and clear. WTF?
Second problem is with performance when the engine is at temperature. The car starts smoothly when cold and drives as it should - drives great actually. New EHA seals, fuel filter, plugs, valve cover gasket, injectors with seals, resealed fuel distributor, replaced cat with straight pipe, new OVP relay, new MAS, and several other recent maintenance items. When the car gets warmed up however, it will stumble and misfire off the line. It will barely accelerate at any degree of pedal pressure and will stumble harder the more you press the gas. Once rolling up past about 10mph the car again drives fine. The workaround I have figured out is to hold the gas down a bit with my foot on the brake at lights or stop signs, or while in traffic - as if about to do a brake stand. If I hold it at 1100rpms for about three seconds, it idles smoothly again and will take off from the stop smoothly. The car will start hot, but requires a bit more cranking. If you crank until it seems to fire up it will go up to idle and then die immediately - holding the key in the start position for about two or three seconds will keep it at idle and it will stay idling smoothly. The car always idles smoothly regardless of engine temperature. Big WTF.
Any help or ideas would be very sincerely appreciated. Both problems are getting severely annoying.
