e39 523i misfiring, wont accellerate properly

BigglesPiP · 10 Mar 2010 at 20:49

It's quite possible to confidently diagnose the other half of the things which can trigger this sort of problem with basic tools (as per the edit I just made to my last post).

Reading the codes is not the logical 1st step for a DIY mechanic, as it costs an hours labour. For me it might well be as I have easy access to a FIAT examiner. But the likes of the OP want to rule out the simple stuff 1st.

Edit:
Although there's other steps I'd have gone through before buying a set of plugs.

DannyW · 10 Mar 2010 at 21:02

it might be an air leak actually because i found a pipe coming off the inlet manifold that had lots of insulation tape around it

Moeks · 10 Mar 2010 at 21:05

I would check every piece of hose and pipe you can find for holes or splits while you're at it.

[TW]Fox · 10 Mar 2010 at 21:06

DannyW said:
it might be an air leak actually because i found a pipe coming off the inlet manifold that had lots of insulation tape around it

Surely not as you told us it wasn't a bodged nail, hence its price, but a perfectly maintained car?

BigglesPiP · 10 Mar 2010 at 21:06

Manifold Vacuum pipe, I don't know how many there's supposed to be on these, but that pipe just lying there will be at least tampering with the air metering. I'm going to go look for some sort of workshop manual..

Edit: Best I can find is a BWM forum doing a group purchase of the workshop manuals. Are they not into posting sly PDFs or am I just not looking in the right places?

[TW]Fox · 10 Mar 2010 at 21:08

Which pipe is it? Can you point it out on a picture?

Your engine will be slightly different to this but you can give us an idea?

CaPtBlaCk · 10 Mar 2010 at 22:27

BigglesPiP said:
What's to say there is a fault logged? That motor is from before misfire detection was implemented, so a fault with the coils or plugs (which I think is most likely) probably won't show a fault.

FYI it has both primary and secondary misfire detection. In any case fault codes should always be the first step in diagnosis, especially one that appears to be sporadic in nature.

BigglesPiP · 10 Mar 2010 at 22:38

CaPtBlaCk said:
FYI it has both primary and secondary misfire detection. In any case fault codes should always be the first step in diagnosis, especially one that appears to be sporadic in nature.

Is that the bosch system with the sensor on the strut top?

And I still maintain that fault code reading is not the first step for a DIY mechanic. A professional with a code reader handy; yes, but for john down the road with a socket set and a multimeter there's a lot of symptoms which can be followed through to a quick and easy cure which does not need the codes reading, even if there's a fault light on the dash.

Take the BBoB problem on my 146, yea there's a fault light on, but wait, the plugs for these relays are all furry, lets salvage some wiring pats from the inside of a car in the local scrap yard. £10, a length of my insulating tape, some heat-shrink and an hour of soldering, now the problem is gone. Should I have paid £50 to get the codes read before I mended the well documented and vastly common fault?

CaPtBlaCk · 10 Mar 2010 at 22:43

The symtoms are sporadic in nature hence logged fault codes are the best place to start. Of course trawling the forums may also throw up useful information however in this case it has not prevented a 'guess not test' form of troubleshooting.

BigglesPiP · 10 Mar 2010 at 22:48

I do agree that he shouldn't have just started buying parts, there's more could be done. He says in the OP that it still has a slightly hunting idle when he stops. I'd have started looking at air-metering and coil's supplies there, but the pipe revelation kind of overrides all of that.

[TW]Fox · 10 Mar 2010 at 22:52

BigglesPiP said:
And I still maintain that fault code reading is not the first step for a DIY mechanic.

It is with a car like this - its not a basic Fiat.

Should I have paid £50 to get the codes read before I mended the well documented and vastly common fault?

Why pay £50? You can buy the cables for 20 quid and use a laptop, job done.

BigglesPiP · 10 Mar 2010 at 23:51

[TW]Fox;16132102 said:
It is with a car like this - its not a basic Fiat.

The care an engine requires is based on factors like the state of tune of the engine, not the brand. If you think BMW motors are any more advanced than other European makes, you're mistaken. Although BMW have little if any engines which you would call a low state of tune.

If I was to legally acquire the cable and alfadiag software including decoding feature, It would cost about £50.

If, someone had a misfire one their 6 cylinder E39, and diagnosed a coil to be the fault by swapping them, then replaced the bad one, this wouldn't make the cheese holing the head gasket on melt. Everyone needs to get it out of their heads that a car can just tell you what's wrong with it, fault codes are far from that.

[TW]Fox · 11 Mar 2010 at 07:51

Nobody has said they will tell you whats wrong with it - its just an obvious and prudent first step in the diagnostic process and is better than just randomly buying new parts to fit in a hope that it will work.

CaPtBlaCk · 11 Mar 2010 at 14:03

BigglesPiP said:
If, someone had a misfire one their 6 cylinder E39, and diagnosed a coil to be the fault by swapping them, then replaced the bad one, this wouldn't make the cheese holing the head gasket on melt. Everyone needs to get it out of their heads that a car can just tell you what's wrong with it, fault codes are far from that.

That is really relevant if we were discussing a permanent misfire. However, that is not the case in this instance, the fault is 'sporadic' in nature hence the reasoning around checking the fault codes first.

DannyW · 11 Mar 2010 at 17:06

the taped up pipe is near the middle of the inlet manifold, gonna try take it off and try seek a replacement

done around 100 miles since changing the plugs car seems to be fine so far but still dont trust it and scared of breaking down lol

Joshy · 11 Mar 2010 at 18:55

[TW]Fox;16133368 said:
Nobody has said they will tell you whats wrong with it - its just an obvious and prudent first step in the diagnostic process and is better than just randomly buying new parts to fit in a hope that it will work.

It is not really changing "random" parts though? An Air filter and Spark plugs are service items, and both could very likely be causing the misfire. Changing them now can only do good even if it doesn't fix the complaint.