1991 318i 5 speed with 294,000 miles on the clock. Now for the problem. Engine at operating temp. Shut the engine off. Wait for 5 to 30 minutes for the underhood temp to rise. Restart engine. Engine idles perfectly for around 15 to 25 seconds then begins to falter and shake violently. Adding more throttle only makes the problem worse. After about 45 to 60 seconds the idle improves and the engine throttles up perfectly and you could not ask for a better running engine. Vapor lock of the fuel rail? I checked the engine on fuel pressure and was normal. Engine off pressure dropped immediately to zero. Replaced pressure regulator. Engine off pressure now drops to 30 psi and rises to 40 psi as underhood temp rises and then settles to 30 psi for 30 minutes or longer. Problem still exists. Replaced o2 sensor. No change. The only fail code that occurs is # 201 o2 sensor control problem and it only occurs when the engine is running poorly and more throttle is added. Also while the problem was occuring I pinched off the fuel return line to raise fuel pressure to around 60 psi and no change was noticed. The problem has to be insuffcient fuel, but why? Any input would be greatly appreciated.
Thanks
Steve
Thanks
Steve
