Hesitant E46

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Hesitant E46

Postby Avdr » Sat Jun 16, 2012 7:54 am

Hi All, hoping to beg a little insight here, particularly if somebody else has come up against this problem...

Got a 3 series E46 in at the moment. Its a 318ti with a N42B20A engine, 2001 but pre EOBD with 86 000 miles.
It arrived as a non runner. Having diagnosed that the timing chain had become slack and jumped some teeth on the ex side, I have replaced the timing gear (ie. guide rails, tensioner - new design of tensioner fitted).
The car now runs well, except for a hesitance off idle that has all the characteristics of a missfire...

Upon getting it started for the first time, this hesitance was immediately apparent. With codes

27DA - Alternator fault
P274E - Unknown (at the moment)
2744 - Missfire Detection cyl 4

The intruiging thing is that this 'missfire' clears completely after 2000rpm, irrespective of load. But still I had to start somewhere, so swapped plug from cyl 1 to cylinder 4, and swapped coil stick from cyl 2 to cyl 4. Cleared faults and tried again, code was set again.
Next I got the scope out and looked at secondary's on cylinder 4 v's cylinder 2, was happy with what I saw.

Next I looked at injectors, 1 v's 4 and again I'm happy with what I saw (electrically atleast). Decided to swap injector 1 for injector 4 and see if the faulty cylinder was now cylinder 1.
I started the car up and was amazed but baffled to find the fault gone, so quickly went out for a test drive and was very happy with the car. Came back turned it off and upon restarting 5 mins later the fault is back. However the code will not set now, the hesitance remains but I simply cannot get the code set.
Had a word with the owner and explained the situation, he informed me the missfire had developed some 10 months before the timing issues and that prior to the timing rebuild it had been much worse than it is now.

Next plan is a fuel pressure test, fuel pump current test and a snap throttle looking at MAF, lambda, and fuel pressure.
Switch rate of lambda is slow, (managed to view live data with texa tool), but I want to be a bit more sure of the fault before I spend someone elses money on parts.

Sorry for the rambling explanation, but any advice welcomed.
Thanks
Andy
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Re: Hesitant E46

Postby Robski » Sat Jun 16, 2012 11:10 am

I think P274E is misfire detection all cylinders.

Can you post the secondary captures that you say " happy with what you saw" all cylinders please ?

Also the injector captures too.

The MAF/TPS/O2 is an excellent idea to see what is happening with the fueling.

Also be nice for a CKP/CMP if poss as i may have this very same issue to look at shortly.

Is the O2 reporting lean at the stage of hesitation ?
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Re: Hesitant E46

Postby Avdr » Sat Jun 16, 2012 12:20 pm

Hi Rob. Was all a bit hurried when I had the scope out, and didn't actually save anything. When I said I was happy with what I saw, I meant comparing cylinder 4 to the other cylinders. I'm going to have another crack at scoping it out as soon as the weather clears up. (will finally have a unit to trade from as of monday - but thats another story).

Will save loads of captures next time and generally spend a little more time working through it.
Have just been out to the car and fitted a new battery, and it ran perfectly at first, but then started to faulter and miss again quite badly - has set the codes again now. In the back of my mind im thinking 'hmm that period of perfect running from cold seems to be about the length of time I would expect the fueling to be in open loop' - so will deffinitely be looking at lambda.

They're a difficult car to diagnose especially with so little serial data available. Double vanos and valvetronic, DBW throttle, quite apart from 'old fasioned' electrical faults there is a host of other potential problem areas to consider.

RE: Alternator fault, I don't know why that is set. Those codes were scanned using just an autel hand held scanner, the texa txt doesn't find the code for alternator, and I have confirmed the battery is charging.
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Re: Hesitant E46

Postby Kev » Sat Jun 16, 2012 6:33 pm

Hi Andy,
No such thing as rambling, any extra info is always helpful! Interestingly I'm quite sure the European Commission stated that all PETROL cars at to be EOBD compliant by the 1st January 2000!! First of all assuming you have no valve damage, there is a couple of issues on the BMWs that might be worth a more detailed look, If any of the ignition coils are of 'Bremi' manufacture number ending in 42/02 BMW states they should be scrapped as they have insulation problems.Your vehicle should have just missed this but there's nothing to say that at some point they hadn't been sourced and fitted. The second thing that's worth a look is the return breather pipe was prone to corrosion which had symptoms similar to your vehicle. The modified replacement breather pipe part No is 111.575.200.35, there are also seals for the same pipe part No 116.175.027.61, hopefully this will keep you quiet for a bit!

Kev
Last edited by Kev on Sat Jun 16, 2012 10:14 pm, edited 1 time in total.
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Re: Hesitant E46

Postby Avdr » Sat Jun 16, 2012 8:26 pm

Hi Kev, thanks for the info there.
Of the 4 ignition coils, 3 are bosch and are all black, 1 apparently is BMW and has a silver coloured shrouding over 2/3 its total length - havn't studied them myself yet, a friend was looking at them while I swapped plugs and I just listened to his observations - will certainly check for bremi part nos.

Could you be a little more specific on return breather, are we talking crankcase venting? Have got the BMW EPC cd, will have to install in and see which pipe you mean.

The car does have the EOBD plug but not the protocol, probably registered late.
No valve damage - engine is not an interferance engine, but did check piston crowns wit borescope to be sure.
In need of a set of adaptors for compression tester to do a proper test, can do a pico relative test in the meantime now that it has a decent battery. Not actually sure how useful a compression test would prove, as the valve lift is reduced at idle I imagine - would still serve to check cylinders against each other.

Since the last post I have been out and done another cold start on car and it did run fine again until it started to warm.
Thanks for the info so far,
Andy
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Re: Hesitant E46

Postby Kev » Sat Jun 16, 2012 10:22 pm

Hi Andy,
All's I know is that it's on the breather system for the crankcase and there is a modified part. You will have to inspect all the breather piping carefully and if you can (easier said than done I know!) clamp it near to the manifold to see if the hesitation goes away! If it does, go through the whole breather system or just order the part and have a look at the shape of it! I know it's a long shot Andy but it's worth a look especially while they have had problems with them!

Cheers Kev
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Re: Hesitant E46

Postby Avdr » Mon Jun 18, 2012 9:45 pm

Right then, the report!

First of all, I was wrong about the car not being EOBD, while the hand held scanner refused to communicate, the txt did communicate in EOBD mode.

Secondly, having spent much of the weekend trying to absorb all relavant info on the engine and it's electrical systems, I have discovered, that the two pre-manifold cat lambda sensors are wideband - and not much use to osciloscope diagnostics. Cylinders 1 & 4 make up bank 1, Cylinders 2 & 3 make up bank 2. Each bank has a pre cat sensor, then on bank 1 there is a narrowband post manifold cat lambda, then a second narrowband lambda further down the system after the main cat.

Again following cold starts over the weekend the car was perfect for 3 minutes - this timescale is very repeatable - every cold start leads to 3 minutes of perfect running.

I have today taken captures, of all secondary signals, and then a set of four further captures of primary v secondary for each cylinder.

Havn't yet been able to test fuel pressure, but it seems to me that if its ok for 3 minutes its hardly likely to develop a fault later on?
3 coils are Bremi ending 39/01 one is bosch - got that mixed up in previous post.

Robski - I have taken a capture of crankshaft sensor against both camshaft sensors - per your request.

Got a couple of interesting sceen grabs from EOBD mode $01, which show the fuel loops as being open loop even after an extensive period of running.

Having difficulty uploading the waveforms, they seem to get to the end of the upload bar, then the screen refreshes, I lose my typing, and the attachment is nowhere to be seen. Any help appreciated, is there a max file size? Some are quite big.


At a loss for how to proceed, still would like to fit new lambda's but if i'm wrong its £180 down the line in one fell swoop.
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Re: Hesitant E46

Postby Kev » Mon Jun 18, 2012 11:52 pm

Hi Andy,
Don't buy any lambda sensors just yet, you say the fuel loop is open even after the engine has been running for some time, I would go back to EOBD at this stage to see if any codes are logged. The reason I say this is that some systems will stay in 'open loop' if there are any faults stored. If there are no faults stored and the system is still in open loop then have a look at the coolant temperature reading. check to see if it's coming up at approx the engine temperature. If it stays very low it will stay in 'open loop' and the engine will be receiving an over rich mixture because the engine ECU still thinks that the engine temperature is very cold and fuels accordingly, this would also cause uneven running as the engine would now be requiring a leaner mixture. because in real terms the engine would be getting hotter and a richer mixture is no longer needed. This would also show up on a gas analyser. I would stick my neck out and say I'm quite sure that you don't have a fuel pressure problem, but you can just bare it in mind for the time being! The wideband lambda sensors are better diagnosed through the serial port using your scan tool.

check that Andy, maybe Robs got a bit more info for you! Kev
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Re: Hesitant E46

Postby Avdr » Tue Jun 19, 2012 7:18 am

Hi Kev, thanks for the info.
Have attached a screen grab from EOBD mode. It doesn't show any faults in EOBD ever, (note the grab shows MIL on but no stored codes?) except for when I tried swapping B1 lambda for bank 2 lambda - it actually figured out I had switched them around - I was trying to determine if this would change around what I saw in the attached grab, how can one bank be closed loop and the other open due to driving conditions (ie. hard accel) when I hadn't even touched the throttle. Madness haha

EDIT: should add, when I say swapped the sensors around, I mean the wires not the physical sensor. Ie. bank 1 sensor was plugged into bank 2 wiring, and visa versa
Attachments
e46 o2loopjpeg.JPG
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Re: Hesitant E46

Postby Robski » Tue Jun 19, 2012 3:42 pm

Andy

Thanks for taking the time & effort grabbing CMP/CKP, typically the jobs off now but will always be handy in the library.

I would still like to see the primary/secondary captures at misfire to determine the type of miss.
If the files are too large save 1 page from the file where its at actual fault & post, or if you wish PM for my email addy & i'll take a look that way & maybe trim & post for you or email back so you can post,just tell me whats what in the capture.

Force the system rich/lean & monitor the O2's via serial data, you could check with the scope but would mean a bit of faffing with the wiring !
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