Mystery Missfire.

[Mrmigs2011]

Hi all,

Wondering if anyone has any ideas where to look next since I've tried virtually everything....

New plugs
Gaskets
Dinan coils
Vac lines
Pressure converters
Clean map/tmap
And much more,

Waiting for smoke tester to arrive but can't understand this car at all.

Purchased it cheap in a sorry state albeit full history and a nice list of work done,

Wastegate actuators worn to balls
30ff all the time
All vac lines collapsed
Pressure converters dead
Rough idle.

Now after tearing through it all have a 90 percent healthy motor that rips through WOT.

I can't seem to understand why on earth I'm getting missfires during idle when warm, and some slight stutters when off boost, been pulling my hair out for weeks, the motor pulls cleanly and promptly to WOT every time without fail.

Now on MHD 1

Any advice appreciated,

Below is a wot pull. Excuse the throttle closures my puny se spec 35i came on skinny little 17 alloys forgot to disable the DTC so it's a little... Skittish

And another of my c110 scanner, wondering if there's a way I can verify the function of the map sensor ? The kpa value does rise under load.

Many thanks
Michael

 

[Jmantx]

How did you clean the map sensor? BMW sensors can be quite picky at times, and even maf cleaner can cause problems. I also know that I had misfires at idle or when cruising under 2500 rpm before I replaced my injectors.

 

[Mrmigs2011]

How did you clean the map sensor? BMW sensors can be quite picky at times, and even maf cleaner can cause problems. I also know that I had misfires at idle or when cruising under 2500 rpm before I replaced my injectors.

I used an electronic contact cleaner as to hopefully not damage any of the sensors, I have another map on the way though.

Hmm I've been hit and miss about the injectors, so far I've had no visual indicators to say their failing, plugs are all an even colour, they were all dry after pulling them from overnight stand,

Maybe next I should look into the seals and decouplers?

 

[Jmantx]

I used an electronic contact cleaner as to hopefully not damage any of the sensors, I have another map on the way though.

Hmm I've been hit and miss about the injectors, so far I've had no visual indicators to say their failing, plugs are all an even colour, they were all dry after pulling them from overnight stand,

Maybe next I should look into the seals and decouplers?

My plugs looked fine and were dry, but my injectors looked horrible. I had a persistent cylinder 6 misfire, and cylinder 6 had the worst injector. Which injectors do you have?

 

[Mrmigs2011]

My plugs looked fine and were dry, but my injectors looked horrible. I had a persistent cylinder 6 misfire, and cylinder 6 had the worst injector. Which injectors do you have?

I have a set of ind 10s and do agree, I reckon the injectors will look like crap possibly distorting the spray pattern,

At the moment the dme shows no missfire, I get no codes, no nothing, the dme is happy with the rough running because its inside of the smooth running tolerance mostly.

Every now and then you can see the odd injector go slightly out of tolerance.

The inlet was caked in carbon so it's likely to assume my injectors are pretty bad too?

The biggest change I made to smoothness was to run a 1mm gap on the stock coils (on the tripples), this near enough stopped the heavy stutter and made it a light stutter. I have the nkgs to order to see if this will help matters at all as I ordered the Bosch stamped plugs not the BMW ones (not sure if there's a difference).

 

[NoGuru]

Two things that came to mind that I have read causing misfires is the Valve cover.

And I am not sure what trans you have but I have a DCT and the Dual mass flywheel was worn and I had switched to a single mass which resolved misfires for me.

 

[Mrmigs2011]

Two things that came to mind that I have read causing misfires is the Valve cover.

And I am not sure what trans you have but I have a DCT and the Dual mass flywheel was worn and I had switched to a single mass which resolved misfires for me.

True the rocker gasket was done not long ago. I wonder if the garage fractured it ?

And manual trans, although im not sure how I can confirm the fly would cause missing ?

 

[matreyia]

Hi all,

Wondering if anyone has any ideas where to look next since I've tried virtually everything....

New plugs
Gaskets
Dinan coils
Vac lines
Pressure converters
Clean map/tmap
And much more,

Waiting for smoke tester to arrive but can't understand this car at all.

Purchased it cheap in a sorry state albeit full history and a nice list of work done,

Wastegate actuators worn to balls
30ff all the time
All vac lines collapsed
Pressure converters dead
Rough idle.

Now after tearing through it all have a 90 percent healthy motor that rips through WOT.

I can't seem to understand why on earth I'm getting missfires during idle when warm, and some slight stutters when off boost, been pulling my hair out for weeks, the motor pulls cleanly and promptly to WOT every time without fail.

Now on MHD 1

Any advice appreciated,

Below is a wot pull. Excuse the throttle closures my puny se spec 35i came on skinny little 17 alloys forgot to disable the DTC so it's a little... Skittish

And another of my c110 scanner, wondering if there's a way I can verify the function of the map sensor ? The kpa value does rise under load.

Many thanks
Michael

You should tell us which cylinders are misfired.

 

[matreyia]

I used an electronic contact cleaner as to hopefully not damage any of the sensors, I have another map on the way though.

Hmm I've been hit and miss about the injectors, so far I've had no visual indicators to say their failing, plugs are all an even colour, they were all dry after pulling them from overnight stand,

Maybe next I should look into the seals and decouplers?

You cleaned maf sensor with contact cleaner and not maf sensor spray? You should not have done this.

 

[Mrmigs2011]

You should tell us which cylinders are misfired.

No cylinders are missfiring according to dme, this is the problem called 'mystery missfire'

You cleaned maf sensor with contact cleaner and not maf sensor spray? You should not have done this.

Agree to disagree, tmap is working great after being cleaned by it. I just need to verify the data being read is correct.

 

[NoGuru]

True the rocker gasket was done not long ago. I wonder if the garage fractured it ?

And manual trans, although im not sure how I can confirm the fly would cause missing ?

Not sure if you are duel or single mass but the duel has bushings that can wear out quickly at higher HP cars. This was causing me to get a misfire on Cyl 6 at higher RPM.

 

[matreyia]

No cylinders are missfiring according to dme, this is the problem called 'mystery missfire'



Agree to disagree, tmap is working great after being cleaned by it. I just need to verify the data being read is correct.

Electric cleaner leaves a white film after drying. Be advised.

 

[Mrmigs2011]

Electric cleaner leaves a white film after drying. Be advised.

I'll get a can ordered and retry (Y)

Not sure if you are duel or single mass but the duel has bushings that can wear out quickly at higher HP cars. This was causing me to get a misfire on Cyl 6 at higher RPM.

I will try get you a video of smooth running system and the exhaust to try hear what's happening.

 

[Mrmigs2011]

Ok sorry for the lack of updates, busy with work yada yada....

So anyway swapped in another map sensor on the Mani, car drove much stronger after this although still suffered minor hickups at idle, moving forward I'm going to try a set of ngks, pull the injectors and try another wallnut blast to see if I can get a bit more crud out.

Earlier on I decided to put the car properly through its paces to see if I could force any faults, what I found after a substantial amount of abuse was power loss, looking at my logs there's a fair amount of timing correction, even though the car targets much lower timing anyway?

What I can assume is the cars hardware is falling behind for just a stage 1 93oct/98 Ron mhd flash?

- IAT overly hot (IC upgrade due?)
- Coolant running hot (radiator upgrade due?)
- Oil temp slightly over 120C (Oil cooler upgrade?)
- Fair amount of timing correction, is this dme related or plug related, I'm assuming with the high coolant temps and high charge temps it's pulling the timing but I thought timing correction occured due to knock events ? There's no missfire codes or eml what so ever so Id like to assume the plugs are firing correctly.

Could this be the stock plugs aren't up to the Mhd stage 1 under mild/heavy load? Or am I just taking the n54 outside it's comfort zone.

Its an SE spec, don't know if the sports bumpers flow better or?

If someone could go through my log to dissect it, would be vastly appreciated, still getting use to this turbo motor lark.

datazap.me | Mrmigs2011 | MaxLoad Stock Hardware

datazap.me

Thanks everyone !