Unstable Idle - BMW Forum

328I99E46 · 02-25-2005, 10:13 PM

HI ALL ITS BEEN A WHILE NOW SINCE I HAVE THIS PROBLEM ITS 328I 99 E46 M52 MY IDLE IS UNSTABLE WHEN ENGINE IS COLD IT WILL BE RUNNING FOR 2 MIN TILL YOU'LL SEE RPM DROOPING TO 700 THEN IT WILL GO UP AND DOWN AGAIN AND DIE RIGHT THERE !! CANT EVEN WARM IT UP =( I THOUGHT IT COULD BE ICV BUT I GAVE IT TO A GUY TO CHECK IT UP AND HE SAID ITS SOMETHIN ELSE INSIDE THE ENGINE NOW THATS GONNNA COST SOME $$$$$$$ ! SO IF ANYBODY WOULD KNOW OR BEEN THRU IT PLEASEE HELP THANXXXXXXX !!!

zibby · 02-26-2005, 01:01 AM

Hi ! You need reprograming DME software. Go to the dealer , tell them about this problem ,they should know it , there was a software error on this cars just need new program . Gonna cost you around $ 100,00 . Good luck !

CiscoKid · 02-26-2005, 07:39 AM

It could also be the ICV

doughboyea · 02-26-2005, 04:24 PM

If your willing to wait, when you reach your next Inspection, do the reprograming then, they probrolly won't charge you the $100 for it. My 1999 328i was doing that shit all the time when i first started her up in the morning. I would drive about a mile and come to a stop light, then the RPM's would drop and then spike and jerk the car forward a bit. Scared the crap out of me, I was reliving the nightmare that my old Benz was doing.

Here were my posts about it:
Post #1
Post #2

Dough

vtr1000 · 02-26-2005, 07:47 PM

Hey 328,
I had the same exact problem! the Idle would roll just like you described. I brought the car to the dealer and they said it was the VANOS unit needed replacement. i was a little skeptical but they replaced it under warranty and that fixed it! Its a 00 328i and I bought used when it started this idle problem but its been fine since they fixed it. Sorry, but it was expensive! about 1200.00 dollars.

k2c69n · 02-26-2005, 08:09 PM

would the o2 sensors cause this at all

CiscoKid · 02-26-2005, 09:24 PM

they could, but it would be very unlikely, because the car runs fine past idle

k2c69n · 02-26-2005, 09:27 PM

when i start mine up when its really cold, it jumps up to 2 then it will go back down and be fine. I should also mention the check engine lights on, so i am going to go to autozone and have them read those codes out.

328I99E46 · 02-26-2005, 11:24 PM

OK THANX GUYS !!!! I JUST CHECKED EVERYTHING REALLLY GOOOD WITH MY FRIEND WHO IS CERTIFIED BMW TECHNICIAN AND GUESS WHAT IT IS VANOS UNIT TO FIX IT ITS A LOT OF $$$$ ABOUT 1200 LIKE THE OTHER GUY SAID HERE ...... OK LATER GUYS !!!

328I99E46 · 07-11-2005, 04:00 PM

MY BAD AFTER A WHILE OF DRIVING I STILL HAVE SOME PROBLEMS WITH IDLE SEEMS LIKE AS IT IS IN PARKING ( P ) OR (N ) AND I STEP ON GAS UP TO 5000 RPM OR 3000 RPM AND LET IT GO AND DO IT FEW TIMES AND ITLL DROOP TO 500 RPM KINDA HEAR ENGINE GOING WRRRRRR WRRRR THEN IT GO UP AND DOWN AND TOP AT LIKE 700 RPM .... KILLLING ME I HAVE REPLACED BATTERY AND VOLTAGE REGULATOR THOUGHT IT COULD BE A PROBLEM BUT ITS NOT MAYBE I REALLYY SHOULD GO AND TALK TO THEM ABOUT THAT DME SOFTWARE REPROGRAMING ????

peterkulesza · 07-11-2005, 05:21 PM

maybe this was obvoius, but :

please try a can of techron injector cleaner, and a dose of isopropanol-based h20 remover....

328I99E46 · 07-11-2005, 06:14 PM

did try the techron injector cleaner what is that isopropanol-based h20 remover where can i find it and how does it look ???? what does it do ?

peterkulesza · 07-11-2005, 09:42 PM

techron:

older cars tend to have some (more or less) deposits from gas and combustion produtcs. this stuff usually looks like brown, dense goo on the injector nozzles, and valves. cumbustion products usally are black carbonized hard crap on insides of valves, and exposed parts of the combustion chambers.

this can cause rough idle, mainly cos injectors cannot atomize gas properly. techron is made of aromatics, plus some nonionic detergents and it cleans all this crap off. made by chevron, recommended by bmw (or used to be).

isopropanol or methanol:

just regular alcohols. the intent here is to remove all water from gas, which happens always. ambient moisture is in the gas tank, and it condenses on the sides, as temperature goes down. water does not mix with gas at all, and occasionally can interfere with smooth flow thru injectors at low delivery volumes.

both alcohols are very hygroscopic, so they mix with water in any proportion. however, isopropanol is better at mixing with gas, whcih is these days mostly aliphatic hydrocarbons. so like it over methanol for that reason.

you can get all of this at autozone or any equivalent car parts store. techron about $5 per bottle, either alcohol about $2. one bottle of each per tankful, and you are done!