random engine power surges m52

[lionkingns]

have a 523i, no engine issues for over a year I had it. last few days the car started having some random loss of power. While driving it will start to sputter and surge in power (pretty violent, turns the asc on from the bumps in power), sometimes it will strugle and have a diesel tractor like sound when you floor it under 2000 rpm, and 2 times at a red light the rpm jumped to about 1500 and than it just dies. I guess its fuel or ignition, just need some guidance where to start looking and checking. I thought it was maybe some dirty fuel, power in about half a tank of fresh from a different fuel station, all the same. All of this is pretty random, it will drive normally for 10 minutes, than choke and surge for 30 seconds, and run good again for 5 minutes, than a minute of issues

[crdiscoverer]

A scan is the first thing you should do. I'm thinking maybe crank or camshaft sensors or even the electronic throttle depending on what year is your 523i.

[lionkingns]

its a cable throttle, 1997. Where to find the idle valve on a M52 ? To me it looks like it could be the issue

[crdiscoverer]

Your engine is almost identical to mine then. The ICV is right under the throttle body. If you have small hands it's not too difficult to remove with the throttle body in place, otherwise you will need to take off the intake boot, MAF, air filter, etc. to get to it. You have to reach blindly and remove one or two screws and a couple of hoses. There are DIYs floating around on how to remove it and clean it.

There's obviously no harm in cleaning the ICV, however, I doubt it will cause power surges.

Have you tried driving with the MAF disconnected? It will run like crap but you will discover if some of the issues you report go away. The cam and crank sensors could also be at fault. My crank sensor (in our euro M52s it's to the right of the AC compressor) once failed and I was getting these awfully bad power "gaps" that felt like somebody was stomping on the brakes for a second. It was very hard to troubleshoot and wasn't clearly showing up in the scanner.

But again, unless you scan for codes it could be anything: dirty injectors, fuel pump, crank/cam sensors, MAF, a vacuum leak, etc.

https://lh6.googleusercontent.com/-g4Q8BOTJrig/UX2ucAVc_oI/AAAAAAAAA9c/C4RfHRZtgig/s912/Modded%2520manifold%25206.jpg

[lionkingns]

after a diagnostic check, it was all down to the crank sensor, which was replaced 11 months ago, gotta love aftermarket parts

[crdiscoverer]

after a diagnostic check, it was all down to the crank sensor, which was replaced 11 months ago, gotta love aftermarket parts

Good to know. Worryingly, the OEM sensor is getting harder and harder to find.