1995 E34 540i Poor Acceleration

[Cambridge]

I’m not getting the power I used to out of my 95 540i. It idles smooth as silk and cruises nicely, but when I punch the accelerator to pass or merge with traffic, it just doesn’t seem to have the power it used to. The exhaust also seems to have a different note when I punch it. I’m used to a smooth turbine-like sound, but now I hear a slight chuffing rhythm in the exhaust. Before it was effortless acceleration, now the engine seems to labor.

Interestingly, about 120 miles or so ago, I replaced the oxygen sensors and plugs. For about 30 miles the car was like a rocket. Smooth, powerful acceleration. Then, while at highway speed, I experienced a short burst of engine knock and an accompanying loss of power. The knock quickly went away in a couple seconds, but the power never came back.

The computer shows two persistent faults: “lambda control #1” and “lambda control #2”

I rechecked the sensors and the plugs, but they seem fine. The car has an Alusil block with 108000 miles. I checked fuel pressure per Bentley and that all checked out.

I’ve heard that the computer needs 150 miles to adjust itself after a sensor change. Could that be the cause of poor performance? Is it possible that this is all because of a bad injector? I’ve also heard that it could be the exhaust gas recirculation control on the back of the intake manifold. (Although there is not much suction when I open the oil filler or pull the dipstick).

Any ideas?

[billB]

Lambda control 1/2: means the DME senses large deviations in the value of air-fuel mixture could be too rich or too lean. Many possibilities as you can imagine such as fuel pressure problems, defective injector, air leak, and problems with the fuel evaporation. I say have a pro check it to minimize this guess work.

Note: when O2 sensor is the problem a different code like 1212 is stored in your DME this so because the DME does NOT read any value (output) from a non operational O2 sensor—bad wires or O2 sensor proper going south…….

regards
billb