VR6 Bora Hesitates on acceleration

[Dyldo]

Howdy dubdubs

OK, here's the issue. At idle, she 'seems' fine and i can rev her t1ts off with no issue. It is at any time under load that she hesitates and misfires (not loudly).

She has brand new coils (Bremi, less than 100kms) and NGK plus (same) and now also has a brand new Bosch MAF (massive props to Goodfella). Still same issue.

I am cleaning the K&N air filter as we speak, but I don't think that will help.

I've come up with a few ideas for what it might be:-
Coil plug wiring harness
fuel pump
lack of V9f supercharger
fuel filter
injectors
ECU

I picked up one of fuzion's Launch CReaders and I have yet to get any codes etc as I have the baby by myself and can't get out there, but anyone have any ideas?

[h100vw]

Baby on the back seat!

Have you fitted the new parts to clear the fault or has the change of parts caused the missfire to start?

Gavin

[Dyldo]

i had a coilpack fail, so had a temporary one in there whilst i ordered 6 newbies from ecs. then i thought i should replace plugs too, and strangely didn't think of a maf. the hesitation, i believe, was not there till i changed the parts - but i can't be 100%.

[Coralon]

I am no mechanic but I would be checking the plug gaps. Under load fuel trims combined with the new MAF may be causing a misfire if one plug is a bit bent. Babies love speed but you must face them forward, in the middle of the back seat so they can truely appreciate what is happening

[h100vw]

I'd try refitting old parts a bit at a time until you work it out. MAF first I guess then maybe do 3 coilpacks then the other 3. Then do the sparkplugs the same way.

Gavin

[Bora _Pies]

I had a similar problem where it would occasionally misfire revving through the gears as well as hard start. I had the oxygen sensor replaced and haven't had any problems since.

Geoff

[Dyldo]

dammit! just plugged my Launch CReader V in and it looks back at me saying "no fault codes". yeah right!!

what should my idle maf amount be (g flow) and peak amount at hard rev? what values should i be looking for in the data stream?

[WhO]

Since you replaced stuff have you reset the ECU / reset the fuel trims? Not sure if it'll help but its worth a shot! A dirty or otherwise non ideal afm would've made the ecu trim to suit and the new afm might be throwing that out as it's no longer suitable for the new maf.

Info about fuel trim's VWVortex.com - Fuel Trim Information

Also resetting your codes (even if there are none) should reset your fuel trims apparently

[Dyldo]

so reset ecu by discon battery for 10mins?

[Dyldo]

hey when i reconnect the battery, i have read that some folk have to realign the TB. is that right? Or does it learn new values?

[WhO]

I'm not sure if disconnecting the ecu will actually reset it, it might but i'm not 100% sure, probably worth a try!

As far as the TB goes, i've never had to re-align it. After plugging in the battery again when you first turn the ignition on you can hear it open and shut a few times to calibrate itself.

[Dyldo]

ok, so how do i reset the ecu?

[WhO]

Just did a whole bunch of web browsing and concensus is that unpugging the battery for 30min-1h seems to do the trick. To be sure i'd clear fault codes before doing this even if there are none (as this is meant to clear fuel trims too) and then unplug the battery. Maybe just unplug it overnight to be sure, cant hurt!

As far as throttle alignment when you plug the battery back in turn the ignition to on and let it sit there for say 10-20 seconds so it can work itself out. Then start it up.

[Dyldo]

UPDATE
OK, I reset the battery overnight, reconnected and heard the TB aligning itself. Started her up after a minute or so, and everything sounded great.
Plugged Launch CReader in and got no fault codes at all (which worries me actually) and then took some values from the data stream - see below.
Then I went for a drive, and in 2nd gear went to WOT to get more values in the live data stream - no real change to floor and ceiling values. And then sure enough after a few hundred meters of test we get the hesitation and stuttering, and by the time i get back to my driveway i have a P0305 code (Cyl 5 misfire) - which I am sure is not the only fault code but i am not learned enough with the Launch yet.
Calling JMAC!!

Anyway, here's some values:-
max g/s flow of MAF - 120
idle flow of MAF approx 3.5 to 4.0 g/s
engine rpm 760
coolant temp 85
short term fuel trim 1 floor of (12%) to ceiling of 12%
short term fuel trim 2 floor of (8%) to ceiling of 7%

I am sure there were more just can't remember them.
Thoughts?

[Dyldo]

oh, and these values are with a brand new MAF and newly-oiled (lightly) air filter, and the new plugs and coils as mentioned.

I think I remember timing at idle was 12deg?