[torrque]

Hi,

I am experiencing a lot of shaking and bucking when accelerating; I bought the car with the premise that it has a bad computer, and it has a new one now... Re-programmed MSD81.

So the car has new injectors (index-12 all of them) , new plugs, new battery, new alternator, it has had the walnut blast clean. It has the HPFP and LPFP changed also.

Problem is, since I swapped the DME's, (previous owner's mechanic advised on DME swap) I am throwing no codes anymore, and it still bucks, stops like crazy from time to time. It's like you hit a wall, rpm needle drops to zero, and it recovers immediately. The warmer the engine is, more often it does.
In extreme cases, engine stalls completely, but start up fine.

It also idles nice, no shaking, no uneven idle.
I am suspecting throttle body, as I revved it a couple of times on the spot, and when the problem occurred I heard the blow off valves going off, so throttle body closing although I was accelerating ... I have one on order from Ebay, trying with a good second hand unit first before I splash on a new one.

any other suggestions ? Again, after adapting the new DME, and running for a while, I have no error codes. Although I did had initially sticky a throttle body adaption error and throttle body error... But I thought those wore just due to new DME .

Many thanks

Edit: Editing first post as requested. I have gone through months of frustration and knuckles damaged, and some paid work with no results so far...

I am reaching the end of humanly possible patience ... so far this has been done:
Both hpfp and lpfp pumps and sensors swapped
New battery, new alternator
New injectors, new coils new plugs
New Crank angle sensor, new camshaft sensors
swapped EKPM module, no changes, sent new one back
New throttle body, no change
Wiring to crank angle sensor completely renewed, including the connecting plug, all the way to DME, no change.
walnut blasting done previously by owner, checked to be true, opened up intake and took a movie of valves conditions, very clean
New front cats (not brand new, but in good condition), removed secondary cats (found front cats completely collapsed, stuck into secondary cats).
New O2 sensors
New water pump and thermostat

Car is running the second DME which was purchased off a crashed 535i (MSD81). Problem has not changed since the DME swap, but there is a questionable amount of trust on the old DME I programmed.
Considering replacing the DME with a good known one from a BMW specialist, which is my last hope... That or car going to be dismantled.

Will post back....
Thanks for all who contributed and tried to help me out of my misery...

[Faredo]

Im guessing issue with plugs still or coils. its strange youre not getting any misfire codes though.
what plugs are you using? what gap?

[torrque]

Originally Posted by Faredo

Im guessing issue with plugs still or coils. its strange youre not getting any misfire codes though.
what plugs are you using? what gap?

They are the OEM plugs, and they looked to be gapped OK, I didn't actually measure, just pulled them out to make sure they are new, and they look brand new...
That's the thing, I had this car before, and ran through misfires and plugs,coil packs and eventually full injector set with it, it always throws a misfire code when it does...

I don't think it's a misfire in my case, it does not feel like one.
Engine never hesitates like a misfire, simply stalls completely and recovers.

[torrque]

Plugs are exactly these:

https://www.ecstuning.com/b-genuine-...12120037244kt/

[Faredo]

Man you cant eyeball a .022 gap. go pick up a:

[torrque]

Originally Posted by Faredo

Man you cant eyeball a .022 gap. go pick up a:

Got a few of these, I am a mechanic so 4 were perfect, I had to adjust 2 of them... Same difference. It 's not a misfire, as I said...

Changed Low pressure fuel pump (previous replacement was with a second hand unit, so I just put in a new one as I had it handy) , high pressure fuel pump sensor. Readings on high pressure fuel pump are perfect now... I have no codes, still bucking.

USPS is delaying my package with the throttle body; argh... waiting is kiling me. I highly suspect that SOB, but if you have any other ideas please post .

Many thanks

[torrque]

Originally Posted by Faredo

Man you cant eyeball a .022 gap. go pick up a:

How is your intercooler working, is it much better than stock ? Did you monitor intake air temps before and after ? I am thinking of one if I ever get to the bottom of this issue that is... Thanks!

[Faredo]

Originally Posted by torrque

How is your intercooler working, is it much better than stock ? Did you monitor intake air temps before and after ? I am thinking of one if I ever get to the bottom of this issue that is... Thanks!

Logs are comparable to other 7" street cores. Honestly, go with whoever is offering the better deal. Here is a small review i did some months back http://www.e90post.com/forums/showthread.php?t=1393512

[torrque]

anyone happened to have any other ideas; the lack of error codes drives me crazy... still waiting on the throttle body. I opened up the old one on the car, and something is definitely amiss. The big sprocket that transfer the movement from the motor to the butterfly valve is loose up and down on the shaft, and you can hear it inside the body with the cap on clicking , going up and down. I am pretty sure it's missing a plastic washer or something that used to hold it in place....

[torrque]

Hey guys,

I replaced the throttle body, same problem ! It's killing me, what else should I look at ?

The lack of codes is driving me nuts. It seems to be happening more on the 50% travel on the acceleration pedal, if I floor it, it does not buck. Happens on steady throttle and accelerating also, so no relation to boost or turbo spooling. Sometimes I just lift the throttle and I see the rpm needle just drop rapidly to zero, and recover ?

Thanks for any and all input

[torrque]

Now it has a new symptom, it also shuts down at times when it's warmed up properly, this feels like a fueling issue to me ? Darn. Problem is, still no codes!

[MysticRob]

You keep saying it's not showing any codes, but what are you using to pull them? Might be a generic code reader problem, or since you replaced the DME already, maybe it's not working correctly. Has that DME ever worked properly? Who programmed it?

Did you code the injectors properly?

You mention buying a fleabay throttle body, did you do the same with the DME? I will once again throw it out there that you can't trust used parts like that to be in good shape, so the TB is still suspect in my mind, and of course the DME if purchased in the same way.

[torrque]

Originally Posted by MysticRob

You keep saying it's not showing any codes, but what are you using to pull them? Might be a generic code reader problem, or since you replaced the DME already, maybe it's not working correctly. Has that DME ever worked properly? Who programmed it?

Did you code the injectors properly?

You mention buying a fleabay throttle body, did you do the same with the DME? I will once again throw it out there that you can't trust used parts like that to be in good shape, so the TB is still suspect in my mind, and of course the DME if purchased in the same way.

Hi,
I am using INPA to pull codes, and or Carly for BMW pro... Both show codes, when there are any. For example I took of the accelerator pedal to see if the pot in there is showing good values and measure it, and fired up the engine; got 3 error codes for accelerator pedal. I also have error codes for front brakes being low, but nothing else showing a clue about the problem/cutout.

The Throttle body I bought new, from rockauto.com... exactly the same issue (changed my mind about second had part, and bought new; installed it yesterday).
The guy who programmed my DME is Guillermo, from N54tech.com board, he is well know into doing this for ages. I used a good second hand MSD81 from a crashed 2009 or so 535i.... It runs fine otherwise, and I can't suspect the DME as problem is EXACTLY the same as with the old one... I mean car starts perfectly fine, you think of pushing the button and off it goes.
I have a feeling that the cutout is an issue caused by power to the DME itself, so I will try to look into the DME relay swap and wiring...

Thanks for any input.

[torrque]

actually, how can I test the DME relay offline; it's going to be hard, as it cuts out more when it warms up, so I would need to leave power to it for a while; need a 12 V supply...

[MysticRob]

How did you even diagnose the original DME was bad? Or did you? Like you just said, doubtful you have 2 bad DMEs at this point, so issue is likely elsewhere.

I'll ask again, did you verify the injectors are properly coded? Are you sure they're really -12s and not some fleabay knock-offs? Where'd you get them? What else on the car was changed before you apparently bought it back? You mentioned blow-off valves. What other mods? Vacuum lines in good shape? Logs?

[torrque]

Originally Posted by MysticRob

How did you even diagnose the original DME was bad? Or did you? Like you just said, doubtful you have 2 bad DMEs at this point, so issue is likely elsewhere.

I'll ask again, did you verify the injectors are properly coded? Are you sure they're really -12s and not some fleabay knock-offs? Where'd you get them? What else on the car was changed before you apparently bought it back? You mentioned blow-off valves. What other mods? Vacuum lines in good shape? Logs?

yes, properly coded, brand new OEM injectors. It would not even idle properly if it's an injector problem... I changed all vacuum lines, all new. The DME diagnosis was done by German Performance in North Boston, and I bought the car with the "DME issue ". But they were wrong; although they did have a DME intermittent connection when they tried to scan it, because I know what the problem is. It's electrical, not a misfire.

This is because I logged today some parameters with Carly; and when the hiccup occurs, all values are zero, 0, nada. This means DME goes OFFLINE, presumably with all injectors, as they are run by the same relay. This is also the reason I don't get any codes, because the DME cannot point to itself when it has no power, it's clueless that he's going offline
I swapped that relay with a new one, same issue..

So the 100$ question now; what else is supplying power to the DME, that can intermittently drop for a split second?

[torrque]

Calculated air mass Fuel pump Fuel pump to request Measured air mass
325.551819 60.046387 17.000000 147.437500
401.513916 55.052185 15.000000 131.718750
70.536232 49.810791 2.000000 32.812500
0.000000 0.000000 0.000000 25.656250


See last line ? that is the blip. Apart from the air mass, which most likely comes from another sensor, all other drop to zero when it stutters, and RPM needle also drops to zero, indicating total stop.
When it warms up well, the failure causes the engine to stall completely; I have to restart it ...

[MysticRob]

Originally Posted by torrque

yes, properly coded, brand new OEM injectors. It would not even idle properly if it's an injector problem... I changed all vacuum lines, all new. The DME diagnosis was done by German Performance in North Boston, and I bought the car with the "DME issue ". But they were wrong; although they did have a DME intermittent connection when they tried to scan it, because I know what the problem is. It's electrical, not a misfire.

This is because I logged today some parameters with Carly; and when the hiccup occurs, all values are zero, 0, nada. This means DME goes OFFLINE, presumably with all injectors, as they are run by the same relay. This is also the reason I don't get any codes, because the DME cannot point to itself when it has no power, it's clueless that he's going offline
I swapped that relay with a new one, same issue..

So the 100$ question now; what else is supplying power to the DME, that can intermittently drop for a split second?

Well, you're closer now from what it sounds like.
I would look at grounds and connectors on that poor thing.
May not be a stoppage of power per se, but maybe power being available and just not getting to where it needs to go.

[torrque]

Thank you; apart from battery connections, and the ground strap on engine bay, what else do we have for known electrical stuff to check on these cars? I mean, where could it be leaking current .

I also need to check the alternator, it seems to have been replaced by previous owner, but shop wrote "owner supplied" , so I am bit suspect on this one.

[MJ80.]

Hey mate not sure how much help this will be but fuck it.

Back in the day, years ago now i had a procede tune on my n54 it never ever worked properly from day 1, second hand unit. It would drive fine except if i redlined the car, or at times any time the rpms went over 5k at wot only. The car would buck and jerk so violently it felt like you had hit a wall, at times it would hit redline and just shut off entirely. I never ever found a workaround or made sense of the random codes that would get thrown every now and then. I gave up and renoved the tune and moved to mhd and never had the problem again even at much much higher power levels. I guess if theres anything that might suggest its that it could be purely software or electronics given that my extreme violent jerks stopped with a software/tune.

Good luck.

[autoart]

You say you bought the car with a bad computer. Does it have a clear title? could it be a flood car? How long have you owned it?

[torrque]

Originally Posted by autoart

You say you bought the car with a bad computer. Does it have a clear title? could it be a flood car? How long have you owned it?

Yep, clear title, 2 owners, looks very clean.... The guy really liked it and forked over 5g in the summer on it on new injectors, water pump, thermostat, alternator, battery, Bilstein shocks, HPFP recall, HPFP sensor, etc. Then he hit this problem and shop recommended DME swap; and he decided to sell it as is. I decided to buy it for a discount as I am a troubleshooter by hobby and here we are