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      08-03-2015, 10:55 AM   #1
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Revs drop off throttle to point of stalling at stop

Update aug16:

Well replaced O2 sensors and no change in the searching idle when coming to a stop.
Took the car on a 2 hour hiway run at steady 130kmph(80+/-mph) today and lo and behold the searching is gone.
Possibly adaptations from the revised tune?
Anyways on to more data logging to perfect the tune.............and incidently the car feels way quicker


Hopefully the collective experience here can help me solve an ongoing problem with my rich fuel condition. I don't think it is strictly FI related.
Engine will start easily from cold and idle at 10-11afr for 10 seconds then slowly climb to stoic and be rock stable.
After driving for a short whole and stopping or off throttle the afr drops to 10 or less(my analog gauge goes to 10) and car can stall if the throttle isn't blipped.

Also at cruising speed with cruise control on the afr' s will bounce between 11-14.

I have done a simple soapy water leak test with no apparent leaks.
Vacuum to BPV is strong(not verified amount with gauge)
Codes pulled are:
Error Codes Present On August 2, 2015 11:53:51 AM Code,Type,Description DME,DME Number: 2796,1,Throttle: adaptation values incorrect 29B5,4,Secondary-air system 2760,2,Secondary-air system 27D0,2,Firing, cylinder 5
I do have a slight leak at the valve cover gasket which was confirmed with the soapy water.

What is everyones thoughts. I can't ask the tuner to write me a reliable tune with this problem lingering.



This video is a representation of the rev drop.
What is causing the sucking sound?
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Last edited by Steeler; 08-16-2015 at 07:38 PM.. Reason: Update
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      08-03-2015, 11:53 AM   #2
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Dave, have you replaced your MAF recently? I believe we discussed it a while back, but I can't remember. You could try unplugging it to see if the problem persists.

The problem could also be an O2 sensor that's on its way out. Based on a misfire in cylinder 5, I'd look at bank 2. The O2 sensors (including the one hooked to your AFR gauge) won't give accurate readings until fully warmed up, which takes 30 seconds or more. I'd ignore them on cold start and let the car run for a few minutes first.

Is the secondary air pump plugged in as it should be? Mine has come unplugged before.

If it's a boost leak, the symptoms would get worse at higher rpm (more boost) but shouldn't be present at idle unless the leak is severe (like a main pipe detached). A smoke test would tell you for sure. The smoke test pressurizes the intake piping to a small degree, and you should see it leaking out anywhere there's a hole/loose pipe. Unplugging the MAF should isolate the problem to either a bad MAF or a boost leak if your idle stabilizes. The car may stall at mid/high rpm if you have a severe boost leak and the MAF is unplugged.
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      08-03-2015, 12:06 PM   #3
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Thanks Josh,
Yep new MAF, I will try unplugging and note any difference.

This vid was shot after engine oil was at 180f so sensors are fully warmed.
SAP has been removed for 2 years and has a block off plate.

Update:

MAF unplugged and a short test drive cures the issues.
Time for new O2 sensors?
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Last edited by Steeler; 08-03-2015 at 12:46 PM.. Reason: Added info
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      08-03-2015, 01:03 PM   #4
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I'm leaning towards major boost leak. A smoke test is your best bet.

If you can hear a whistle and alpha-n / speed density mode (which ignores the MAF) cures the issue, I think unmetered air is getting in.
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      08-03-2015, 01:06 PM   #5
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By the way, I probably used "boost leak" too generically. It could be a leak on the unpressurized side... pretty much anywhere after the MAF.
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      08-03-2015, 01:42 PM   #6
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Quote:
Originally Posted by pokeybritches View Post
I'm leaning towards major boost leak. A smoke test is your best bet.

If you can hear a whistle and alpha-n / speed density mode (which ignores the MAF) cures the issue, I think unmetered air is getting in.
Update:
So I went to clear the code thrown by the MAF being unplugged and there is now codes for 27Dx firing cyl 3,5&6.



Not really a whistle Josh, more of a huff.
Can you hear that on the vid?

I soaked the heck out of all connections before, after and at the IM with no sign of leaks.
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Last edited by Steeler; 08-03-2015 at 01:54 PM..
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      08-03-2015, 07:30 PM   #7
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Ignition coils?
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      08-03-2015, 07:34 PM   #8
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Anything is possible Ian, replaced coils and plugs last year.
I will replace the O2 sensors first as they are original AFAIK and work back from there.
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      08-03-2015, 09:46 PM   #9
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Not likely then...
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      08-04-2015, 07:29 AM   #10
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Those misfires are from different banks, and I doubt both O2's would fail at the same time.

Did you reset the codes after unplugging the MAF? If the codes were present before unplugging the MAF, but not after, it could be either the MAF or a boost leak.

Did you go with OEM when you replaced the MAF?
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      08-04-2015, 08:00 AM   #11
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Thanks Josh,

MAF is BMW, no MAF codes unless unplugged.
The idle issue at stop gets worse the warmer the engine gets. Also an abrupt loss of power at around 4k under WOT
I have to disagree on the O2's not failing at the same time if they are both original.
Plan on doing
O2's
Checking coils
Checking and recapping plugs.
Replacing VCG

What should gap be?
The turbo guys go really tight but also run 16-24#
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      08-04-2015, 08:45 AM   #12
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I don't believe you set the gap on OEM plugs. I have bought non-OEM plugs before (can't remember off the top of my head what the gap was set to), but replaced them with OEM when I installed the supercharger.

Can you describe the behavior of the car with the MAF unplugged?

After clearing the codes, do the misfire codes return with the MAF unplugged?
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      08-04-2015, 08:51 AM   #13
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Quote:
Originally Posted by pokeybritches View Post
I don't believe you set the gap on OEM plugs. I have bought non-OEM plugs before (can't remember off the top of my head what the gap was set to), but replaced them with OEM when I installed the supercharger.

Can you describe the behavior of the car with the MAF unplugged?

After clearing the codes, do the misfire codes return with the MAF unplugged?
VF sent a different set of plugs(hotter or colder I cannot remember) which I did check the gap and set to OEM specs.
I have read that an FI engine should have a closer gap plug!!!

The engine when the MAF is unplugged has no "lag" from off to on throttle and has no "burble" upon letting off the gas. It is obviously down on power due to the ECU controlling the AFR and not the O2 sensors, but there is no sign of stumbling or idle dropping as when MAF plugged in.
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      08-04-2015, 10:07 AM   #14
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I would:

1. Check your MAF wiring harness to make sure there are no shorts or exposed wires. Focus on where the MAF harness was extended for the VF kit.

2. Try a different MAF sensor. I can send you mine for testing purposes, as I don't plan to drive the car in the next few weeks. As you know, MAF sensors are expensive and vendors won't let you return them if they have been installed.

If it works fine with a different MAF, you know the MAF is bad. At that point I'd look at what caused two sensors to go bad in as many years (probably the harness).

Have you oiled the filter or cleaned the MAF recently?
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      08-04-2015, 05:11 PM   #15
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Quote:
Originally Posted by pokeybritches View Post
I would:

1. Check your MAF wiring harness to make sure there are no shorts or exposed wires. Focus on where the MAF harness was extended for the VF kit.

2. Try a different MAF sensor. I can send you mine for testing purposes, as I don't plan to drive the car in the next few weeks. As you know, MAF sensors are expensive and vendors won't let you return them if they have been installed.

If it works fine with a different MAF, you know the MAF is bad. At that point I'd look at what caused two sensors to go bad in as many years (probably the harness).

Have you oiled the filter or cleaned the MAF recently?

Josh thanks for the help on this.Hopefully others will have use for this discussion in the future.

MAF wiring was traced and confirmed good in the winter time, all joints were soldered and individually shrink sleeved then wrapped into a bundle. Resistor was left inline as instructed by VF

The MAF being good could still be in question.
I did find a small boost leak at the TB so I went through all the clamps and snugged them down.
I went ahead and made a short vid using the data logger. Does anyone have any input to the values shown in the real time table.

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      08-16-2015, 07:38 PM   #16
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Updated first post
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      01-13-2016, 10:18 AM   #17
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If you still have DISA in your custom setup, that is a likely culprit with this sort of instability near idle. Even INPA will not test the physical functionality of a DISA flap, only the position of the actuator motor, which has a brittle, soft, plastic arm connected to the flap. Just a suggestion - pull that sucker out and make sure the flap is secure with no play. Anodized aluminum replacement parts I used in 2014 on my VF blown M54, still sold by this seller: http://www.ebay.com/itm/400717692839
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      01-13-2016, 11:06 AM   #18
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Quote:
Originally Posted by drewski429 View Post
If you still have DISA in your custom setup, that is a likely culprit with this sort of instability near idle. Even INPA will not test the physical functionality of a DISA flap, only the position of the actuator motor, which has a brittle, soft, plastic arm connected to the flap. Just a suggestion - pull that sucker out and make sure the flap is secure with no play. Anodized aluminum replacement parts I used in 2014 on my VF blown M54, still sold by this seller: http://www.ebay.com/itm/400717692839
Disa is new.
After disassembly of the intake, blower etc. I noticed the ICV was unplugged. I had not plugged it in last spring after stripping down the intake side for other mods.
All will be well in my world when the snow leaves.
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      01-15-2016, 09:42 PM   #19
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So thats it, the ICV being your issue? Man, hope that indeed is it great discussion non the less in this thread. Reminds me to ask either you or Josh where the Maf gets relocated to with this SC install?
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      01-16-2016, 09:33 AM   #20
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Quote:
Originally Posted by Vanne
So thats it, the ICV being your issue? Man, hope that indeed is it great discussion non the less in this thread. Reminds me to ask either you or Josh where the Maf gets relocated to with this SC install?
Mine isn't in the most ideal location. The VF intake system pulls air from down low near the front bumper, and I didn't want to risk hydrolocking the engine so I relocated the filter next to the headlight housing. The MAF is right after the filter. I like the intake and filter location, but the MAF needs a straight shot of piping for as little turbulence as possible in order to give accurate readings. I get a little bit of porpoising on rare occasions that I think is related to disruptions in airflow over the MAF. Finding a new spot for it is on my to do list.
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      01-22-2016, 04:47 PM   #21
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Quote:
Originally Posted by Vanne View Post
So thats it, the ICV being your issue? Man, hope that indeed is it great discussion non the less in this thread. Reminds me to ask either you or Josh where the Maf gets relocated to with this SC install?
If the engine runs good in the spring I won't know for sure if it was the ICV as I am replacing lots of gaskets as maintenance.

As far as my MAF location I fabricated a custom inlet pipe so I could position my MAF just before the radiator cradle and created a pseudo ram air funnel feeding directly into it.
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      04-15-2016, 08:10 AM   #22
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Update

The searching had disappeared when I started her for the first time after the winter.
However the MAF was not plugged in. I plugged the MAF in and the searching returned.
Any comments on this?
Could it be the tune or is it another crappy MAF??
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