Brother acquired a 12' n14 jcw and half the time he goes full throttle it throws a cel/limp mode but no codes and I've tried numerous scanners with no luck.
I did notice it had NO sparkplug guide tubes so he's ordered those. Could that contribute to the issue ?
it has new but with no changes, aluminum valvecover, sparkplugs, noise maker delete , cone filter and forge bov. Along with oil change and coolant flush.
intake isn't cracked , i didnt see any unplugged vacuum lines or anything..
any tips or suggestions ??
Any help is always much appreciated

 

Spray some water or starting fluid over the vacuum lines/intake and double check all intake/intercooler/throttle body piping. If nothing is immediate, check the vacuum lines and air tank under the throttle body. This is usually what caused the issue for me. If not air, double check fuel volume and pressure and then look at spark plug tips and go from there.

 

the plugs I removed DEFINITELY were running lean , which I'd think would lead me towards a vacuum leak. I'd think a fuel pressure code would atleast throw a few error codes atleast it did in my experience.
but good idea with the spray.. I did check vacuum pump line , wastegate line , intercooler hoses and the intake also for cracks and all was ok. Buuuuut I didn't really check the purge valve lines and canister lines.. I did feel if the pcv hose was cracked but it felt ok..
I will be smoke testing it very soon next time he can get it here and I got plug tubes too for him now.

 

Plug tubes replaced with no change.
I smoke tested it and found no vacuum leaks either..
I do notice a squeaky type noise from down below intake manifold, could it be a faulty throttlebody and thats possible the noise in the video or possible a bad pcv ?? Through I can't imagine the stock pcv amd new valvecover both having bad pcv's..

 

If it goes half-power mode after full throttle, I would suspect the high pressure fuel pump. My old R55 would do that when the engine bay would get really hot…. If the half engine light is on, there is a code in there. I’m a little surprised your scanner doesn’t pull it.

 

Even after my HPFP failed almost completely it never gave me any sort of codes. I was scratching my head for weeks before I stumbled on a post with similar issues which were caused by the pump. It very well could be it. My car wouldnt start one day, I didnt have any symptoms or issues before that.


Adam, try swapping the pump from your other car to see if it fixes it, that would be a free way to check for this before spending money on it.

 

both mime are n18 amd his is n14 or I would..
I did find his intake had a crack but I think that'd have caused a low boost code , im doubtful that was the issue and it may have cracked when we removed it to check it. But it went limp mode on his way home too after 1st buying the car before anything was touched so its something I've overlooked..
the car has no starting issue cold or warm and it's rips in 1st and 2nd gear but soon as it goes into full boost is when the limp mode pops up..

 

You could always seal up the crack with some sanding and JB Weld to see if that fixes the issue, if it doesnt, I would check fuel pressure when it is having those issues.
It really sucks our injectors are a pain in the *** to put in after taking them out, giving them a good cleaning may be all it needs if its not the pump. Maybe run some VP Racing Fuel System Cleaner through the system?

 

Thinking about this some more... Does he have a boost-vacuum gauge installed? When my car would do this, I could feather the throttle to keep the boost down, and it would drive OK. Is it actually limp mode, or just boost cut? Does the half-engine get displayed in the gauge cluster? if the half-engine is displayed, then there will be a code. If its boost cut, then there won't be a code stored.

 

no boost gauge yet. It displays the full low power cel on the middle of the tach and the cel comes on on the center gauge too. It's full limp mode , there's 0 boost after it comes on. And it will away on until reset. No amount of drive cycle will reset it
But i grabbed my inpa and laptop so im hoping i can pull a code or see something out of whack..

 

I actually tried that but did wanna spray it then with brake cleaner. It still came on after but he has ordered a new intake.

 

I DID check wastegate and nut was tight and didn't notice any excessive play/slop.. car only has 75k miles..

 

New intake made no difference amd using bimmercode showed no codes either.. this is what's coming on , why wouldn't there be a cel along with the limp mode ???
what gives??

 

Not sure why no codes are coming up. I would try clearing the DME and see if that changes anything.

 

I did do a full reset with my scanner and I got like the maintenance intervals reset and stuff so i think i did clear everything.. only thing I can think to do is hook up inpa n HOPE it brings up a code or fault or shows something that'll point me towards the issue.

 

I’d be seriously leaning towards the fuel pump, but I understand not wanting to throw that cash at a whim

 

wouldn't there be atleast a misfire code with a bad fuelpump? Or a power loss in 1st and 2nd gear ?
what makes it more strange is , after I did all the replacement parts and we went for a test drive afterwards. The car drove PERFECTLY and no cel or anything but then on his way home gutting onto the freeway. BAM !! limp mode again...
do you know what specifically I should look for or monitor with inpa ?? Id guess to watch fuel pressure and boost and see if they fall off when the limp mode pops on..
it ONLY happens when going full throttle and it WONT happen in 1st and 2nd gear. It seems to only be happen under full load or when the car is supposed to make max boost.
we also ordered a inspection camera amd i have a vacuum pump so ille pop out the 02sensor and see if the wastegate seats under correct vacuum too when he brings it back again.
and to check the pcvthe do I suck or blow through the back port ( passenger side rear of valvecover) to determine if the pvc is sealing correctly?? Because i remember my n14 i had limp issues too and the stock valvecover was bad and the aftermarket one was too UNTIL I trimmed the pcv plunger because it was a tad too long and caused a pcv leak, so I wanna make sure that this isn't a pcv issue.
I feel bad for my bro , he hunted for an r58 all fall/winter and then he flies across country and drives it back and he can't even enjoy the car like it's meant to be..
what is your opinion on a valve cleaner spray ?? When I tried it on my n18 and when I removed the cylinder head , it definitely did clean alot off the valves but they still were kinda cooked.

 

I never got a single code when my pump was failing, or with the 2 shitty replacement pumps I got off Ebay. I found that the fuel pressure with the Ultragauge was much lower than it should have been and thats what solidified it for me. Now that I have Lou's Stage X software, I have a way to data log and see how its all doing and ensure that I can pinpoint any issues I have from now on.

 

by chance you know what the pressure should be under load and at idle ?

 

When I was having fuel issues it was showing 126psi for fuel rail pressure on idle, after replacing it, it would show around 1000-1300psi on idle.

Did you change you O2 sensers? I remember that was an issue for me in the past as well.

 

no but I did clean the front 02. I also verified wastegate is good and closes correctly.
unfortunately inpa wouldn't fking connect so im now very limited on diagnostic tools ..
I even tried putting stock valvecover back on ( fixed that odd squeaky noise ,i think it was a bogus pcv ) and i also tried my old divertvalve i know fir certain that was good.
the ONLY change is the squeaky sound is gone BUT now. When it goes I'm limp , after like 2min of normal driving it turns off. .
Wtf

 

Did you mean Bimmerlink? Were any of your other scan tools capable of recovering BMW fault codes?

 

none ! I don't ever even see the cel light come on in the middle under the gps unit , only the low power limp light on the tach.
I've tried torque plus , bimmercode, my handheld scanner , my brothers ghetto handheld , carly and inpa but inpa wouldn't connect at all.

 

Bare with me over here, this thread is bringing back memories, but slowly… When the half power engine light comes on, no in speedo light is displayed, drive the car home but do not turn the engine off. Let it idle while you grab your scan tool and plug it in. If the half power engine light is on, there has to be a code.

If you’ve done, this, then never mind. You’ll have to figure out how to get INPA connected, or take it to the dealer.

Im also a little curious that Carly or Bimmerlink aren’t pulling anything. Carly has been my go to for codes.

 

Unplug multiple different engine sensors one at time. Do any of the unplugged sensors produce an expected fault code?

And if Carly reads live data, use it to monitor/record fuel rail pressure, boost pressure, and mass air flow during a full-throttle pull.