Rough cold start with JB4...

scofike · 11-25-2013, 01:42 PM

I have a 2008 335i with only one mod…the JB4 ISO and am running 27.3 firmware. Over the last several weeks my car has been behaving very poorly on cold starts. Very jerky. RPMs don’t seem to fluctuate according to tach, but you can feel the jerkiness as you accelerate. Almost like it has really bad fuel, or water in it or something. Very rough, even passengers notice it. After a few minutes, or by the time the engine temps reach 160 its evened out, as if what ever it was burned off. From then on it drives fine (Map 1).

I researched on here and found several people having same issue, and the most common culprit was leaking or bad fuel injectors (theory being they were leaking fuel into the cylinders over night and until that burned off, it would run rough). So I made an appt with BMW dealer, and in advance of that I pulled the JB4 out on Saturday morning. Lo and behold, since I took out the tune, I have not noticed the problem (cold start last two mornings). Very bizarre. What would the tune have to do with something like this? Obviously would seem to rule out a mechanical problem, so is there something the tune does that would affect the car’s performance so poorly on cold start?

Thanks for you help…I am going to postpone the BMW service call until I hear what you guys think.

SoFlo_BD · 11-25-2013, 02:19 PM

The tune just increases performance which in turn causes weak points of the car to show themselves.. The problem is there regardless of the tune but the tune just highlights it and makes it more obvious.. How many miles? And when was the last time you changed your spark plugs?

Krells · 11-25-2013, 02:21 PM

I don't think the tune is causing the problem (JB4 here). I have a leaking injector and it is very random. I can go 3-4 days with no cold start issues and then one day it will take several attempts to start. It does seem to get progressively worse. Hopefully I will have some free time in the next few days to replace/code my injector.

Mike@N54Tuning.com · 11-25-2013, 02:47 PM

The JB4 is off during start and idle. Could you of had a loose connection in one of the harnesses? or more likely a fuelling issue. Fuel pump, leaking injector, etc.

Mike

scofike · 11-25-2013, 03:22 PM

I replaced the spark plugs over the summer, so maybe about 6000 miles on them. Car has 62000 miles on it. HPFP replaced when I bought it CPO April 2011.

I am actually very hopeful this is a mechanical problem covered under CPO warranty. I was going to drop it this evening, then they will start it tomorrow and try it out. Fingers crossed it misbehaves in the morning...

FWIW - had walnut blasting done over the summer too at the dealer because I had very uneven acceleration, specifically in the 2000-3000 rpm range (most noticeable running up from standstill thru 50 mph). That seemed to help, but now this issue has cropped up.

Myrder · 11-25-2013, 03:37 PM

Can you read the codes? See if you have some misfires happening. My cold start issue was finicky and would only happen when either temp was below 50, or below 60 mixing e85. I had a leaky #6 injector.

boostaholic786 · 11-26-2013, 01:43 AM

I think I'm having similar issues that your having and did a WOT run and sure enough threw a code (misfire cylinder 6). But very occasional and not all the time whatsoever. But I have already checked the coil and it was fine and I just replaced my plugs about 1000 miles ago so a leaky injector has to be the culprit....

BEAR-AvHistory · 11-26-2013, 02:19 PM

Move up to 27.9. Had some low speed jerky shifting at 2900/3000rpm part throttle; none with the new firmware.

CptJoe732 · 11-26-2013, 09:54 PM

I have a similar problems also. I'm running cobb though. Since its been between 20 and 40 degrees in NJ I thought that may be the problem. My car will fire up fine in 20 degree weather but say if I drive it then let it sit then fire it up it'll take a couple seconds to crank over. But if I start it then turn it off and re crank it, it'll just fire up normally. I'm guessing its left over fuel in the cylinders which is left over from driving but in the cold mornings its either dried up or frozen. Anyone able to confirm this? Didnt mean to hijack your thread I just didnt want to start another thread for a similar problem.

11-25-2013, 01:42 PM	#1
scofike New Member 5 Rep 21 Posts Drives: '08 335i and '22 X3 Join Date: May 2011 Location: Cary, NC iTrader: (0)	Rough cold start with JB4... I have a 2008 335i with only one mod…the JB4 ISO and am running 27.3 firmware. Over the last several weeks my car has been behaving very poorly on cold starts. Very jerky. RPMs don’t seem to fluctuate according to tach, but you can feel the jerkiness as you accelerate. Almost like it has really bad fuel, or water in it or something. Very rough, even passengers notice it. After a few minutes, or by the time the engine temps reach 160 its evened out, as if what ever it was burned off. From then on it drives fine (Map 1). I researched on here and found several people having same issue, and the most common culprit was leaking or bad fuel injectors (theory being they were leaking fuel into the cylinders over night and until that burned off, it would run rough). So I made an appt with BMW dealer, and in advance of that I pulled the JB4 out on Saturday morning. Lo and behold, since I took out the tune, I have not noticed the problem (cold start last two mornings). Very bizarre. What would the tune have to do with something like this? Obviously would seem to rule out a mechanical problem, so is there something the tune does that would affect the car’s performance so poorly on cold start? Thanks for you help…I am going to postpone the BMW service call until I hear what you guys think.
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11-25-2013, 02:19 PM	#2
SoFlo_BD SoFlo_BD 368 Rep 1,749 Posts Drives: 2024 X7 M60i Join Date: Nov 2012 Location: SoFlo iTrader: (9)	The tune just increases performance which in turn causes weak points of the car to show themselves.. The problem is there regardless of the tune but the tune just highlights it and makes it more obvious.. How many miles? And when was the last time you changed your spark plugs? Last edited by SoFlo_BD; 11-25-2013 at 02:25 PM..
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11-25-2013, 02:21 PM	#3
Krells Private First Class 2 Rep 194 Posts Drives: 07 335i Join Date: Jun 2010 Location: Atlanta iTrader: (0)	I don't think the tune is causing the problem (JB4 here). I have a leaking injector and it is very random. I can go 3-4 days with no cold start issues and then one day it will take several attempts to start. It does seem to get progressively worse. Hopefully I will have some free time in the next few days to replace/code my injector.
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11-25-2013, 02:47 PM	#4
Mike@N54Tuning.com Joint Chiefs of Staff 5098 Rep 116,225 Posts Drives: 2007 335i, 2015 M3 Join Date: Dec 2008 Location: N54tuning.com iTrader: (89)	The JB4 is off during start and idle. Could you of had a loose connection in one of the harnesses? or more likely a fuelling issue. Fuel pump, leaking injector, etc. Mike
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11-25-2013, 03:22 PM	#5
scofike New Member 5 Rep 21 Posts Drives: '08 335i and '22 X3 Join Date: May 2011 Location: Cary, NC iTrader: (0)	I replaced the spark plugs over the summer, so maybe about 6000 miles on them. Car has 62000 miles on it. HPFP replaced when I bought it CPO April 2011. I am actually very hopeful this is a mechanical problem covered under CPO warranty. I was going to drop it this evening, then they will start it tomorrow and try it out. Fingers crossed it misbehaves in the morning... FWIW - had walnut blasting done over the summer too at the dealer because I had very uneven acceleration, specifically in the 2000-3000 rpm range (most noticeable running up from standstill thru 50 mph). That seemed to help, but now this issue has cropped up.
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11-25-2013, 03:37 PM	#6
Myrder Major 164 Rep 1,264 Posts Drives: 2010 E92 335i MSport 6MT LMB Join Date: Apr 2013 Location: WildWest iTrader: (1)	Can you read the codes? See if you have some misfires happening. My cold start issue was finicky and would only happen when either temp was below 50, or below 60 mixing e85. I had a leaky #6 injector. __________________ 2010\|335i\|LMB\|E92\|6MT\|MSport\|Logic7\|335is Clutch\|AE Performance\|BMS\|Walbro\|VRSF 7"\| 149.7mph NFZ AZ 1/2mi 1992\|Pontiac Firebird\|Mild 355ci\|T56\| -I will look on your treasures, gypsy. Is this understood?-
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11-26-2013, 01:43 AM	#7
boostaholic786 Captain 40 Rep 622 Posts Drives: E92 N54 with MHD Custom flash Join Date: Dec 2011 Location: Plano TX iTrader: (0)	I think I'm having similar issues that your having and did a WOT run and sure enough threw a code (misfire cylinder 6). But very occasional and not all the time whatsoever. But I have already checked the coil and it was fine and I just replaced my plugs about 1000 miles ago so a leaky injector has to be the culprit.... __________________ [SIZE="2"]Crimson Red E92 335i M-sport 6-speed with MHD custom stage 2+ flash only , 40% E85/93 mix,+ HRE P40S wheels, KW Clubsport, M3 sways,+BMW performance CF Mirrors, BMW Performance CF deck lid spoiler,+ CF interior trim, p3 vent boost gauge,+ LUX angel eyes (11.73@124mph on street tires)
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11-26-2013, 02:19 PM	#8
BEAR-AvHistory 2020 Z4 M40i - 2022 M4C Convt 3174 Rep 5,264 Posts Drives: 2020 Z4 M40i - 2022 M4C Convrt Join Date: Jun 2011 Location: Raleigh, NC - OIB, NC iTrader: (0) Garage List 1965 COBRA (FFR rep ... [8.57] 2023 Jeep Wrangler ... [4.75] 2009 Yamaha V-Star [0.00] Cars 2-BMW, 2-FORD, ... [0.00] 2023 Ford Expeditio ... [0.00] 2020 Z4 M40i [10.00] 2022 BMW M4C [7.25] 1998 FORD Ranger 4X4 [0.00]	Move up to 27.9. Had some low speed jerky shifting at 2900/3000rpm part throttle; none with the new firmware. __________________ Kevin Dravit Gray, Black Leather, Moonlight Roof, Red Calipers 2022 M4C - 2020 Z4 M40i - 2023 FORD Expedition XLT Max 4X4 400BHP - 2009 V-Star - 1998 Ranger 4X4 5MT - 1965 Cobra (R) 5MT - 2023 Jeep Wrangler Sport S 6MT
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11-26-2013, 09:54 PM	#9
CptJoe732 Second Lieutenant 24 Rep 217 Posts Drives: 2007 E90 N54 Join Date: Apr 2013 Location: Toms River NJ iTrader: (0)	I have a similar problems also. I'm running cobb though. Since its been between 20 and 40 degrees in NJ I thought that may be the problem. My car will fire up fine in 20 degree weather but say if I drive it then let it sit then fire it up it'll take a couple seconds to crank over. But if I start it then turn it off and re crank it, it'll just fire up normally. I'm guessing its left over fuel in the cylinders which is left over from driving but in the cold mornings its either dried up or frozen. Anyone able to confirm this? Didnt mean to hijack your thread I just didnt want to start another thread for a similar problem.
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