Another S50 poor idle thread

[R3NNWAGEN]

I have read every thread written about idle problems with m/s5x engines and have come to a dead end. Engine idles fine with no extra load on the engine. Turn the a/c on and the idle will drop and pop back up, sometimes it will level out pretty quick like it should and other times it will bounce up to 1300 and drop to 500 repeatedly. It will do it at night when you turn the lights on and the alternator presents extra load but not as bad as the a/c. Seems to get worse the hotter it gets. On some very hot days last summer it would drop enough it would die. Also it behaves differently sometimes if you are at idle and coasting than it will at a dead stop. Engine is stock except a KA motors intake and turner motorsport swap headers to a custom single 3 inch exhaust, magnaflow cat (very small one) and 2 magnaflow mufflers. O2 sensor is located pre-cat and in a similar location as the e36 as far as I can tell from pictures. Using a 506 dme. I have replaced the O2 sensor, cam sensor, coolant temp, intake air temp, throttle position sensor, both knock sensors, idle control valve and the MAF. Only one I haven't done is the crank sensor. All the rubber hoses, plastic fittings and o-rings for the crank case vent, idle control valve, brake booster and the fuel pressure regulator are new. New intake boot from the MAF to the throttle body. Also replaced the injector seals. All parts are bmw or oem manufacturer, no junk parts. Also found a guy willing to let me try out his 506 dme from his car and the idle was the same. His dme has a turner chip and he also has a dinan chip for it as well, it idled the same on both chips in his dme in my car. I have disconnected and plugged on an individual basis the crank case vent, the fuel pressure regulator, brake booster line and the evap vent on the bottom of the throttle body. Put a vacuum pump on the booster and fuel pressure regulator and they have no leaks. Tried carb cleaner around all the seals and found no leaks. Car passes emissions test no problem. No engine codes as of now. I did have a code for a vacuum leak that I found and fixed when I first tried to tackle this. It was a broken nipple on the brake booster check valve. I'm at a loss and looking for some knowledge on what to try/check next. Any help is appreciated.

[jrockbk]

Have you tried running a 413 red label dme?

[R3NNWAGEN]

I have not. The 413 red dme is from an m50 correct?

[ryanc88]

Have you tested your charging system?

[jrockbk]

Another S50 poor idle thread

Update still having same problems? I'm having random intermittent idle issues as well on my m52 swap, I've cleaned and checked ICV and MAF checked for vac leaks I have and I'm at a loss why my car is acting up especially since it's not consistent with anything els and yes 413 is obd1 m50 dme it can run just about any m5x motor obd1. I'm gonna do a smoke test next

[GDA]

How have you tested injectors for flow/response?

Could one be super weak or dead?

[nrubenstein]

Have you run the wire for the AC idle bump? If you haven't wired that in, it will idle like shit with the AC on. Based on your description, it looks like it runs fine otherwise.

[jrockbk]

Smoke test completed no leaks and problem only crops up after I run car all day shut it down for about an hour and restart it. I'm scratching my head and if I leave it parked overnight and start in morning it's like the problem never existed

[R3NNWAGEN]

Sorry guys, I'm frantically getting the car ready for Bimmerfest and discovered the steering rack was leaking out the drivers side boot about 2 weeks ago so the car has been on stands taken apart. Just got my z3 rack swap finished and have the car back on the road. I did find out while I was under the car that there was only one engine ground wire on the drivers side. I added a second one to the passenger side frame. I acquired a 413 DME to try out. I have not tested the charging system other than watching the voltage on a meter while it does its crappy idle, the voltage was steady it did not jump up and down. I don't remember what the voltage was, it was a few months ago. nrubenstein, unfortunately I did not do the engine swap so I am not sure on the idle bump wire. I had researched that to some extent and read that it wasn't possible to get that working? Maybe that info was for OBD2? Any info on this would be awesome. Thanks for the help guys.

[jrockbk]

So update on strange idle stall and surge... It turns out that I was running the wrong size injectors for my ecu on recent swapped in motor, that gave a super rich condition seemed to mess with the Idle when in closed loop. Problem haven't come back since I changed injectors, btw while at my buddies shop he had an m20 in that exhibited the exact same idle surge and stall problems and it turned out that it was a bad TPS, something else to check for

[R3NNWAGEN]

Finally got around to putting my 413 red label in the car. The idle is much better than before. It drops when you turn it on and it bounces back faster than before. It still will bounce around a bit occasionally but not as bad as before, it stabilizes much faster. I haven't driven it a whole lot as its pretty warm here. I'm still trying to find definitive info on the AC idle bump wire for OBD I.

Aaron

[mpowerful]

I dont run an a/c idle bump and everything is fine. No bouncy idle or anything. I daily my car in new orleans so the a/c is always on.