BMW 4.6 is poor acceleration and hesitation - Page 11

TerminatorX5 · #**101** 08-17-2013, 12:17 AM

another thing about the coils - coils are induction coil devices, with a lot of thin, insulated wire looped (coiled) in circles that will produce a high voltage discharge into the spark plug that will create an electrical arc between the tips of the plug... the thin insulation maybe breached and when the charging voltage is inside the coil, it may not short from one coil to the next through the weakened insulation, but when the engine's RPMs increase, the frequency of the charging process is increasing, thus the periods of no charge are shortening, and as a result, the weakened insulation may give and allow the SOME of the charges to discharge outside of the spark plug inside the coil... this type of the problem might not be visible under multimeter testing, nor under a light load operation... this problem will worsen with time...

my point is, the coils that you are talking about, might be defective nevertheless, even if they work fine now... on the other hand, they might be fine and some other issues are forcing the coil codes... for this thing it is a nice practice to switch the coils from one cylinder to another, and see if the problem moves with the coil...

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Aman · #**102** 08-17-2013, 02:05 AM

I asked him to test all coils before fitting new ones
He said he did and said 3 were completely burnt out...
(He specialises in auto electrics apparently)
What else can I do apart from trust a "professional"...
Shame

Aman · #**103** 08-17-2013, 02:24 AM

Since the catalytic converters have been changed, there were no misfire codes on new or old coils (he did live testing), which is why the new mechanic put the old ones back in.

bcredliner · #**104** 08-17-2013, 12:15 PM

I think you did all you could do to. At least you have some spare coils and you are up and running and ready for a good time ride.

Aman · #**105** 08-17-2013, 12:20 PM

Quote:

Originally Posted by bcredliner

I think you did all you could do to. At least you have some spare coils and you are up and running and ready for a good time ride.

Cheers for all the help and advice

Aman · #**106** 08-17-2013, 12:48 PM

Thank you to Everyone who gave an input in this thread, nomatter how small.
If you are ever in the UK (London) and fancy a beer, send me an email, cheers

Aman · #**107** 08-17-2013, 03:08 PM

Just when I thought everything was ok again...
Was driving home, and check engine light came on and stayed on
One of the mechanics I have met recently was kind enough to offer me to pop by his house so he could scan the codes
I attach a couple of photos
Any idea what this means? Thanks

Aman · #**108** 08-17-2013, 03:16 PM

"Smooth running" values for cylinders 1-4 were all 0.00
"Smooth running" values for cylinders 5-8 were slightly positive
any help with the codes much appreciated (again!)

upallnight · #**109** 08-17-2013, 10:09 PM

Fuel trim is the O2 sensor either adding fuel or taking away fuel. If it reach the limit that it can't add fuel or take any more fuel away it means the mixture is WAAAAAAY off.

I would have the shop perform a fuel pressure test at the fuel rail. Have you ever replace the fuel filter and fuel regulator?

A clogged filter will mean less gas is available so the O2 sensor will try to add gas to the mixture, if it can't add enough gas you get that error code that additive fuel trim has reach the limit.

A rupture fuel regulator would mean the pressure is always too high since at WOT you don't have a high vacuum as compare when the throttle is part open or close. The O2 sensor will try to take away gas but if it can't take away enough gas you get that error code subtractive fuel trim has reach the limit.

Aman · #**110** 08-18-2013, 01:53 AM

Quote:

Originally Posted by upallnight

Fuel trim is the O2 sensor either adding fuel or taking away fuel. If it reach the limit that it can't add fuel or take any more fuel away it means the mixture is WAAAAAAY off.

I would have the shop perform a fuel pressure test at the fuel rail. Have you ever replace the fuel filter and fuel regulator?

A clogged filter will mean less gas is available so the O2 sensor will try to add gas to the mixture, if it can't add enough gas you get that error code that additive fuel trim has reach the limit.

A rupture fuel regulator would mean the pressure is always too high since at WOT you don't have a high vacuum as compare when the throttle is part open or close. The O2 sensor will try to take away gas but if it can't take away enough gas you get that error code subtractive fuel trim has reach the limit.

Thanks for your reply. Sorry if I'm asking obvious questions as I don't possess a great deal of knowledge on these things, but is there any reason why cylinder 1-4 have smooth running values of 0.00 and cylinders 5-8 have values of 0.02-0.3? It seems bank 1 is running ok? Wouldn't a clogged filter or ruptured regulator affect all 8 cylinders? Thanks for any advice in advance

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