I have a 1996 E300 diesel. Two weeks ago I started the car normally and drove on the freeway, everything normal. At one point I felt a change in the way the engine was delivering power but the car continued to operate fine at freeway speeds. When I slowed down I found that the engine did not idle at exactly 700 rpm as it always did in the past, it slowed to less than 500 rpm, surged up to about 800 and finally settled down to 700. The engine idles rough compared to how it was before and sometimes the engine dies when at idle or when I put the car in gear.

Now when the car is stopped and I step on the accelerator the car lags several seconds before the engine starts to accelerate. It has so little power at low speeds that if I am on an incline, the car will not move at all and has even rolled backwards on me. Sometimes the engine dies when I try to accelerate from idle.

Once I get going and the rpm’s get up to 1,000 or so, the power kicks in and the engine is almost normal, it is able to accelerate to freeway speeds and runs just fine at 70 mph. I may feel a little roughness at speed but the engine runs fine.

The problem is less serious when I first start the car in the morning but after a while it gets so bad that the car is essentially undriveable. I will be sitting at a stop light, the light changes and it takes so long to get moving that the drivers behind me start honking and waving at me with one finger. Since once I get to about 15 mph the car is running fine and will accelerate and travel with the traffic, it really makes me look like an idiot.

I have cleaned the tank screen and changed the fuel filter. I looked at the air filter, it is nearly new and clean but I blew it out anyway. I removed the air intake crossover pipe that carries air from the air filter to the intake manifold. It is clear and the vacuum driven flapper valve is open. I made sure the flapper valve can move freely and put a little oil on it.

I have seen references in the forum to the ALDA. The 1996 car is normally aspirated, if it has that part could someone tell me what it is and where to look for it?

It seems to me like I used to see the vacuum cylinder and arm of the flapper valve on the crossover pipe move more or less continually when the car idled, now there is no movement at all. If I pinch the vacuum hose that is connected to the air filter box it does cause the flapper to move so the vacuum hoses appear to be all hooked up and since that does not happen if I don’t pinch the hose I am pretty sure the air flow through the air filter box is clear.

I removed the EGR pipe between the exhaust manifold. When I started the engine it ran the same. I removed the EGR unit, cleaned it, put a little light oil on the plunger and made sure it seems to move freely, all seems OK but I don’t know how to judge if EGR is working properly or not.

My “Check Engine” light is not on and no codes are showing up.

My mechanic and I have been messing with this for three weeks now and we can’t figure out what is wrong. Any ideas?