what could cause this weird idle behavior on a E36?

bmdbley'sBro · 10-31-2012, 02:58 PM

idles all over the place, but constantly climbs up to 1500 rpm's sitting at an intersection.
now it surges up & down 1200-1500, 1200, 1500.
ICV was just replaced - still doing it.

I recall I had this behavior when an 02 sensor went bad waaayy back.
anywho the car is turbo'd but this all going on while not in boost but in stock vacume, especially when its idling at a stop light..

Ideas?

*oh, also any one got a peak scanner?

sb_600 · 10-31-2012, 03:47 PM

sounds like a vacuum leak to me

bmdbley'sBro · 10-31-2012, 04:30 PM

Quote:

Originally Posted by sb_600

sounds like a vacuum leak to me

thats what i thought too - but nothing can be heard leak wise.

I read about a tricky to find brake booster or master cylinder vac leak - how would one tell if that was the cause?

sb_600 · 10-31-2012, 04:34 PM

yeah you won't hear the leak.

spray some brake cleaner or something flammable that will evaporate on all your vacuum lines (make sure you don't get it on your headers or it'll burn!) if you idle surges, that's where your leak is.

also check the intake elbow - those are known to crack over time.

I can't remember what the brake booster/MC trick is..... sorry!

Goodtohave · 10-31-2012, 07:57 PM

If you want to check the O2 sensor just unplug it from the other end under the hood.

Easy to do...I drove my M50 525 for over a year with the O2 sensor unplugged.

bmdbley'sBro · 11-01-2012, 09:09 PM

So, got in there & uncliped the rear 02 sensor - didn't help anything.

I'll get my codes later:

Reading BMW Fuel Injection Fault Codes
http://www.pelicanparts.com/BMW/tech...de_Reading.htm

sb_600 · 11-01-2012, 09:22 PM

The rear o2 won't do anything. All it does is make sure the cat works properly. You need to try the front one

jeffrie · 11-01-2012, 11:13 PM

How does it respond to a little throttle and how does it act with boost when idel is surging? Any miss or hesitation to rev up off idel or sluggishness till boost kicks in under load?

Blackedout95 · 11-01-2012, 11:57 PM

Its not incredibly common but here's a thought!

Unplug you TPS and see what happens

From there plug it back in and your TPS should be reading .07-8 at idle if I recall (you mentioned it happened when sitting). I would then if confirmed that is not reading correctly ( higher than .07-.08v at idle) look at the actual TB rod, would bet you have a flat spot and rod needs adjusting... You see if the reading is higher it has to have gotten that reading from somewhere

So adjust the rod angle or new TB, either way and retest v output.

Again just a shot in the dark but if all the obvious first things don't pan out, take a look. GL hope is something simple.

bmdbley'sBro · 11-02-2012, 07:45 PM

Quote:

Originally Posted by sb_600

The rear o2 won't do anything. All it does is make sure the cat works properly. You need to try the front one

I have a wideband o2 where the primary should be. before that it was going to a af/gauge ..so the check engine light has Always been on. but the idling this high & reving up & down at 1500rpm is new.

Quote:

Originally Posted by jeffrie

How does it respond to a little throttle and how does it act with boost when idel is surging? Any miss or hesitation to rev up off idel or sluggishness till boost kicks in under load?

it actually did feel like the car was squating on decel & lifting on throtle at low speeds..? rest of the q's require details: cars was running mint forever @7lbs. got rpm to install a wideband02, walboro pump & larger injectors from a v8. he said there was a nick in an injector wire & it was konking out when testing - he fixed that. car ran great for weeks. I eventually hooked up with barry to retune for 14.5 -15lbs. things went wonky. first we couldn't get the manual boost controller to give us more than 10lbs. he/we thought leak or messed up spring in the wastegate or b.controller. during this the car developed Stuttering at low boost. after barry hooked up a leak tester to my intake tubing to see if we could see what was up. we discoverd that 20+psi was blowing oil back Up my turbo feed line & that my turbo is leaking on the intake side. we stopped there. rpm put in new plugs & hooked intake cleaner up to the fuel rail. car ran better, boosted Higher before hesitation, or hickup. which could be over boost, boost leak, turbo leaking oil, fuxored spring or idk wtf...

then the high idle started it now does it 90% of the time

Quote:

Originally Posted by Blackedout95

Its not incredibly common but here's a thought!

Unplug you TPS and see what happens

From there plug it back in and your TPS should be reading .07-8 at idle if I recall (you mentioned it happened when sitting). I would then if confirmed that is not reading correctly ( higher than .07-.08v at idle) look at the actual TB rod, would bet you have a flat spot and rod needs adjusting... You see if the reading is higher it has to have gotten that reading from somewhere

So adjust the rod angle or new TB, either way and retest v output.

Again just a shot in the dark but if all the obvious first things don't pan out, take a look. GL hope is something simple.

unplugged it still idled high. but the car was still cold. don't have a volt/amp tester so I can't check its values..

-
did the fault code thing, if i did it right, it kept repeating 1222 'Oxygen Sensor Lean/Rich Detect (primary)'

will do it again, shut it off before it cleared as it seemed to just be repeating 1222 over & over forever...

Anybody want a rusty crusty project car?

Blackedout95 · 11-02-2012, 08:15 PM

That code is common when the car detects a lean or rich condition, what it points to is what we have already discussed above like vac leak, maf, TB etc and including an O2 sensor but not for sure as again could be other things and not the 02.

Bottom line car is runing rich or lean and with a simple volt check of the TPS you can rule out the TB

Better yet take theTB off and inspect it and clean it, look for flat spots on the rod. Nothing but time and some cleaner involved.

I am sure a mechanic would do that check for a minimal fee and considering you have yet to find the issue it may just be the TB or 02...while your in a shop get the data on the MAF while running, that too could cause the issue and in about 5 minutes if you were near me I could hook up the vedis and see what type of MAF number you are showing.

bmdbley'sBro · 11-10-2012, 06:33 PM

so: the tps unplugged with the car warm saw idles of 2100rpm.

anywho so the car was back at rpm he found a Gasket leak at the start of the charge/intake piping right near the turbo, changed that. also said my Blow off valve seems weak, which might also explain the hi idle & why i could not get above 10lbs..

so...guess i need to test/replace my blow off valve..
I'm going to replace the leaking turbo with hopefully something Cheap & factory on another car.

Blackedout95 · 11-10-2012, 08:43 PM

So was that it,gasket leak, idle down now?