tonton 3 Report post Posted November 11, 2020 Hey guys, it's a long story but basically from what I've been told and what I've seen on my friend's car.. -car wasn't starting at all initially, and me and my friend narrowed it down to the cam position sensors. along the way, we replaced all 6 spark plugs, the battery, and 2 ignition coils as the car was misfiring. -replaced the CPS, car starts and drives fine. -after a day or two, the car threw a CEL and the car still drove fine, but on cold starts, the rpm surges between 700~1.2k. its not a gradual fluctuation but sharp surges and the whole car was shaking when it does that. -scanned vehicle, MAF sensor fault code. -This was done without me, my friend tested the voltages and resistances on the maf sensor, and traced the wiring back to the dme, no faults in the wiring but there were fluctuating readings on the maf sensor. he then decided to replace the maf sensor. He then cleared the codes, and the CEL still came back on. -I looked at it again, and I reset the DME adaptations. CEL never came back on. But now, the car hesitates to accelerate. The first two days felt as if the car was relearning, so I let it be. Then on the 3rd day, my friend said that on the m/way, the car refused to rev past 3k and it felt like it was in limp mode, but there was no CEL -Scanned it again, and now it shows mixture control faults. We pulled the coil packs and ignition loom out and tested the resistances, all good. Specs and tolerances were sourced from a "somewhat trusted russian site" as newtis has been ordered by BMW AG to be closed down. -Checked spark plug compartments, clean. Checked spark plugs for fouling, good. -Put everything back together, and today after work, we started the car and it immediately shut off on us 4 times. Started the car for the 5th time, this time giving it revs , and car stays alive but the CEL came back on. MAF sensor fault again. And this time, everytime we stepped on the brake pedal while vehicle is in P, the rpm surges really hard. When we put it into gear, the gearbox "crashes" into gear, literally. It made a massive thud sound and the whole car jerked forward a little but after putting it in gear, the idle stays at 800rpm and the needle moves up and down a little between 750~850 rpm. That's pretty much it as of now. We're pretty stumped. Hopefully someone here can shed some light on this matter. We plan to look at the fuel pump, o2 sensor, and the vacuum lines over the weekends. Cheers and apologies for the wall of text! Quote Share this post Link to post Share on other sites
Jacko 2154 Report post Posted November 11, 2020 Does it have a massive vacuum leak? One of the CCV lines maybe? Quote Share this post Link to post Share on other sites
F10er 65 Report post Posted November 13, 2020 +1 for vacuum leaks. With those mixture and air mass faults, it almost certainly has a leak somewhere. Smoke testing is the best way to find vacuum leaks. Quote Share this post Link to post Share on other sites
tonton 3 Report post Posted November 16, 2020 hi, we don't have a smoke machine so may need to get one, or borrow one. will check vacuum lines again over the weekends and report back. cheers! Quote Share this post Link to post Share on other sites
Driftit 2078 Report post Posted November 16, 2020 You can also make one. Few guides out there. But I would say it is a vacuum leak too. The CCV may have failed.https://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E90/ENGINE-Crankcase_Breather_Valve_Replacement/ENGINE-Crankcase_Breather_Valve_Replacement.htm Quote Share this post Link to post Share on other sites
