Q: 1995 BMW M3 won't pass smog at idle, random misfire, new coils, plugs, injectors, knock sensors, tested sensors with scan tool

asked by on July 01, 2017

I have a random sputter at idle, won't pass smog at idle 200/100HC, passes at 2500rpm. tested sensors with scan tool and all are working new gaskets and hoses new bosch ignition coils new injectors new knock sensors new o2 sensor(only 1 on car, pre cat) fuel pressure regulator fuel filter tested computer and dinan and Turner chip re timed engine 3 times along with smoke test 3 times swapped MAF and no change( 2 good ones off friends car) only things I haven't replaced are fuel pump(tested with fuel pressure gauge at 51 psi) before fuel pressure regulator throttle position sensor and vanos solenoid/vanos ICV(cleaned a couple months ago, I live on west coast and had another e36 have a very rough idle from ICV getting salt buildup) the problem is it is so slight and random most shops don't even know it's misfiring but it just won't pass smog Thanks for reading and if you have multiple options I will perform all today that are possible thank you!!

My car has 200000 miles.
My car has a manual transmission.

Since you have replaced so many parts , it would be very difficult to determine what exactly is causing this without performing a physical inspection. I wouild stronly recommend having your vehicle inspected by a qualified professional to trace down what is causing this issue. Consider YourMechanic as vehicle inspections can be performed at your home or office.

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