95 E34 540i Smooth Idle, But 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. (Sensors were Bosch, plugs were Bosch platinum+4) 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?

[632 Regal]

disconnect the battery and cross the cables for 30 minutes to re-set the computer. Re start the car, let it idle for a few minutes and then drive as usual, this should at least reclibrate the computer for the current condition of the system. Post the results when done.

[Tiger]

Bosch Plat +4 is always a bad idea on BMW engine. People have problems.

[tim s]

when i bought it, & it made a noticable difference to me after i installed the correct plugs.
tim s.

[grave77]

since there a noticable change in the exhaust note, i think that you need to check the catalytic converter as it seems like blocking the outlet of your engine.

[Cambridge]

when i bought it, & it made a noticable difference to me after i installed the correct plugs.
tim s.

Did you notice the change in all areas of performance? Did it improve acceleration? Or the idle?

[Cambridge]

disconnect the battery and cross the cables for 30 minutes to re-set the computer. Re start the car, let it idle for a few minutes and then drive as usual, this should at least reclibrate the computer for the current condition of the system. Post the results when done.

Does this reset the transmission computer, too?

[DueyT]

Bosch Plat +4 is always a bad idea on BMW engine. People have problems.

Ich concurren...or, I agree, with Tiger! Plat-4 bad...NGK good.

[tim s]

but i am obsessed with my car being right.
my mech. would only sell me bosch since they where oem.
tim s.

[Cambridge]

Bosch Plat +4 is always a bad idea on BMW engine. People have problems.

Just went back. Pulled out the plat +4's and installed new OEM Bosch. So far no change in performance...