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Author Topic: jittery at low rpms. and check engine light  (Read 10325 times)

mas325i

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jittery at low rpms. and check engine light
« on: September 24, 2013, 03:13:50 AM »

hi there! i finally got my 94 325i turbo project done. i have the whole turbo tuning package.

at the moment when i first start from a stop, it has a hard time wanting move or continue to run at low rpms. once i get going and i floor it. its perfectly fine, spools up smooth. my wideband is pegging 10 at full boost right now at 8psi but i plan on turning it up a few to 10 or 11. but i dont have a clue as to where to start for the jittery start from a dead stop. also (may be causing the jittery feeling) the check engine light is on at idle, but when i go and step on the gas, at any range, it goes away. i have a code reader and its telling me its the MAF?? any solutions?



besides those problems, all i have to do is enrich the fuel for cruising speeds. and she's pretty much good to go! cant wait!




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lagwagon

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Re: jittery at low rpms. and check engine light
« Reply #1 on: September 24, 2013, 08:10:48 AM »

Try disconnecting your ICV and also try giving some more fuel to acceleration enrichment in the low rpm range.. I had a stuttering issue and doing this fixed it
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mas325i

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Re: jittery at low rpms. and check engine light
« Reply #2 on: September 24, 2013, 12:40:01 PM »

alright ill give that a shot!


any ideas on the check engine light for the MAF?? like i said at idle its there, i rev it and it goes away until i let off. the moment i let off the throttle it comes back on. when im cruising down the road its on but then when i hit the gas it goes away
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mas325i

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Re: jittery at low rpms. and check engine light
« Reply #3 on: September 25, 2013, 02:49:31 AM »

ok so, check engine light was a result of me not having the ICV even plummed into the intake system. once i did that, BOOM! check engine light goes away. haven't driven it yet since this was fixed so i don't know if the acceleration problem is still there or not (i work night shift so racing up and down the road isn't a good idea at 4am. don't want to piss off the neighbors)

BUT! i still have an issue with it idling, and its only when she gets close to operating temp. it leans out, starts starving for fuel. fixes itself and idles up, then a few seconds later i can watch my wide band lean out again to where it doesn't even register
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millerperformance

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Re: jittery at low rpms. and check engine light
« Reply #4 on: September 25, 2013, 10:10:20 AM »

How far away is your O2 sensor from the turbine outlet? What happens if you simply turn the O2 sensor off in the software?
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mas325i

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Re: jittery at low rpms. and check engine light
« Reply #5 on: September 25, 2013, 12:39:39 PM »

factory o2 is in its factory location. i made sure to put it where the wires reached. ill have to try shutting off the 02 i guess. maybe thats why its leaning out?
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millerperformance

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Re: jittery at low rpms. and check engine light
« Reply #6 on: September 25, 2013, 03:51:05 PM »

We recommend putting the O2 sensor NO FURTHER than 18" from the turbo. You have to remember, even more so, if using a tubular manifold, you have so much more tubing for the exhaust gases to travel before it gets to your O2 sensor. The closer the O2 sensor is to the turbine, the better. O2 sensors need heat and the hotter the exhaust the more accurate it will be.

Many times we see weird idle problems related to O2 sensor placement and or O2 heater relay problems.
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Candy4M3

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Re: jittery at low rpms. and check engine light
« Reply #7 on: September 25, 2013, 04:08:33 PM »

I hope I'm not thread jacking here, but i thought it was relevant. I'm also having similar issues. My idle is set to 1,000 rpm and is afr is spot on at 14.7 when shes cold, she idles great.
As soon as she reaches close to operating temp my idle drops down a bit to around 800 rpm, and afr climbs to around 16.5 then finally to 17.2 and stays there. 
My O2 sensor is 11" away from turbo, i've tested it with O2 off to see if there is a change and no change.
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millerperformance

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Re: jittery at low rpms. and check engine light
« Reply #8 on: September 25, 2013, 04:14:05 PM »

I hope I'm not thread jacking here, but i thought it was relevant. I'm also having similar issues. My idle is set to 1,000 rpm and is afr is spot on at 14.7 when shes cold, she idles great.
As soon as she reaches close to operating temp my idle drops down a bit to around 800 rpm, and afr climbs to around 16.5 then finally to 17.2 and stays there. 
My O2 sensor is 11" away from turbo, i've tested it with O2 off to see if there is a change and no change.

Have you been able to add fuel with the WAR Chip and richen it up?
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Candy4M3

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Re: jittery at low rpms. and check engine light
« Reply #9 on: September 25, 2013, 04:26:36 PM »

i made a copy of my main tune with fuel enriched at idle. I can see the difference when its cold. but once it gets to operating temp afr goes back up to 17.2. I even tried raising my fuel pressure from my pressure regulator just to get some sort of live feed, but it still stays floating around 16.5-17.2 even with a 10psi increase in pressure.
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mas325i

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Re: jittery at low rpms. and check engine light
« Reply #10 on: September 26, 2013, 03:48:30 AM »

well i may or may not have gotten mine fixed. ill know more tomorrow after i start it up and let her warm up again. i changed the plugs to a one step colder plug(even though i wasnt having an issue with them before) started the car up and she did the same thing once it got warm, choked at idle.. so with it running i disconnected the ICV, rpms went up to about 1100 at idle. i let it run for a while to see if it would change. nothing happened just stayed at 1100rpms. so i plugged it back in, rpms went everywhere for a few seconds. i snapped the throttle and it came back down. idles just fine now. just to see if it was a fluke thing. i shut it off. waited 20 seconds. started her back up and still idles fine. i wont know until tomorrow when its cold, and start it up again and see what happens when it gets warm again.

BTW at idle (after i unplugged the ICV and plugged it back in) my wideband was reading mid 10's and staying there.
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Candy4M3

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Re: jittery at low rpms. and check engine light
« Reply #11 on: September 26, 2013, 03:49:50 PM »

I have an update as well.

At first i had both maps identical, and rpm was set to 1000. The only difference was I had O2 off on map 1, and O2 on for map 2. No change, idle still dropped to ~600 and AFR shoots lean.

I then lowered rpm to 960 on map 2, and for some reason everything is good. The rpm stays where it needs to be and my AFR doesn't shoot up.
Now i'm in the process of changing my idle values to get closer to 14.7. I have no idea whats the difference, but it works for me. As soon as i get my idle afr good ill take it for a drive and report back.
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mas325i

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Re: jittery at low rpms. and check engine light
« Reply #12 on: September 27, 2013, 02:28:50 AM »

well mine still choked when it got warm after my little test the other night, un-hooking the ICV seemed to work and it drives down the road like a dream. AFR could be a little better during cruising speeds when im not on the throttle, but since my O2 is in its factory location and not within 18'' of the turbine, im going to try and shut that off this weekend and see what happens. i would like to be able to be rescued if something goes wrong so the weekend is my only option to test everything
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