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Usually poor fuel injector performance, a fouled/ failing MAF, aftermarket intake or exhaust are responsible for high fuel dilution.
In the cases where these have been rules out, the driving factor is usually mechanical in nature, with combustion byproducts and raw fuel being allowed to bypass the critical seal between piston rings and cylinder walls. If the above conditions are present, they can create a lack of ring seal that can further drive the issue.
Thanks for that info. The injectors are less than a year old, the MAF is less than two years old, the intake is factory and the only exhaust mod is a set of TechArt mufflers which have been on the car for around 10 years, maybe longer. 🤷
I'll throw out another idea, maybe bores are ovalized at the top and causing leak down and some blow by, allowing more fuel into the oil than normal?
That thought had occurred to me but wouldn’t there also be some oil consumption associated with that? I’ve owned the car for almost 8 years and she’s never had a noticeable use of oil.
That thought had occurred to me but wouldn’t there also be some oil consumption associated with that? I’ve owned the car for almost 8 years and she’s never had a noticeable use of oil.
The bores ovalize more at the top than the bottom. So the oil rings see little deformation, so in theory should still control the oil consumption
The bores ovalize more at the top than the bottom. So the oil rings see little deformation, so in theory should still control the oil consumption
80% of oil control comes from the 2nd ring. The oil control ring measures the amount of oil delivered to the bore, but it doesn't determine oil consumption.
BTW- A MAF that is 2 years old isn't considered new.. They can last a shorter amount of time than this, or become fouled.
What injectors were used a year ago? Were they new? Rebuilt/ cleaned?
80% of oil control comes from the 2nd ring. The oil control ring measures the amount of oil delivered to the bore, but it doesn't determine oil consumption.
BTW- A MAF that is 2 years old isn't considered new.. They can last a shorter amount of time than this, or become fouled.
What injectors were used a year ago? Were they new? Rebuilt/ cleaned?
The injectors were brand new Bosch 996.2-style.
I’ll get some Durametric readings on the fuel trims and MAF and post them here.
The plot thickens. Today my Durametric showed a P1123 code though I’ve not had any CEL occurrences. I cleared it and went for a drive to log some data. Lo and behold, the code returned after I got back from the drive.
I just post these as reference to you, or others who come cross this, as to what the TRA/FRA numbers mean.
Maybe a yours is running little rich? You might also look at what your MAF air mass numbers are (kg/h).
I have read through those before but thanks for posting them to read again. Here’s my kg/h at hot idle today with the AC Off. MAF appears to be ok since my 720 rpm idle is about 20 rpm above spec (680 +-20).
Every time I have seen this scenario it has been a faulty MAF sensor...( but this could be the exception so test fuel pressure first )
Test the fuel pressure and the pressure regulator, and make sure the vacuum hose to the regulator is hooked up and functioning...it should lower the pressure when hooked up.
The CEL set-point for code p1123 is -0.36 ms for the TRA fuel trim, you are right at it on one bank with -0.35ms.. and not to far away on the other at -0.30ms
Your injection time is 2.4ms .. then is lowered by .35ms on bank 1 and by .30ms on bank 2
Also your "specified air mass" is 12kg/hr with a "specified air adaption" of -3kg/hr for tank venting so the expected air mass of 15 kg/hr but your MAF is sending a signal of 18.5 kg/hr.......15kg/hr is the norm for the 3.4..
I would test the fuel pressure/regulator to confirm they are good, then substitute a known good MAF to confirm the fuel trims go back to near 0...
Every time I have seen this scenario it has been a faulty MAF sensor...( but this could be the exception so test fuel pressure first )
Test the fuel pressure and the pressure regulator, and make sure the vacuum hose to the regulator is hooked up and functioning...it should lower the pressure when hooked up.
The CEL set-point for code p1123 is -0.36 ms for the TRA fuel trim, you are right at it on one bank with -0.35ms.. and not to far away on the other at -0.30ms
Your injection time is 2.4ms .. then is lowered by .35ms on bank 1 and by .30ms on bank 2
Also your "specified air mass" is 12kg/hr with a "specified air adaption" of -3kg/hr for tank venting so the expected air mass of 15 kg/hr but your MAF is sending a signal of 18.5 kg/hr.......15kg/hr is the norm for the 3.4..
I would test the fuel pressure/regulator to confirm they are good, then substitute a known good MAF to confirm the fuel trims go back to near 0...
The car threw more codes today after a cold start. P1123, just as before, and now P1319 and P1318. Thr car was audibly rough running this time under load while at low rpm’s for a few various moments until it fully warmed up. Still no CEL has presented itself….yet.
I’m working on procuring a fuel pressure tester but I did remove the vacuum line from the fuel pressure regulator. The rubber connector that attaches to the regulator was slightly moist on the inside with fuel. Wouldn’t this indicate that there is possibly unmetered fuel entering the engine via this vacuum line?
We kept the vacuum line removed (and plugged) and then ran the fuel pump: once using the Durametric activation and once with the engine running. We expected some fuel to spurt out of the top of the regular but none did. Maybe it has a leak that only presents itself under vacuum (and not simply with the vacuum line removed)?
Interestingly, when we removed the vacuum line from the fuel pressure regular, the high MAF kg/h readings didn’t correct themselves. The car still idled between 680rpm and 720rpm and the kg/h varied from 18.75 to 22.0. If there was an unmetered fuel leak, wouldn’t those number have immediately corrected themselves after removing the vacuum line to the regulator (and therefore removing any unmetered fuel from the equation)?
Possibly the membrane inside the fpr is pinholed and fuel is entering the vacuum line but I would be very surprised if it only happens with the line connected to fpr and plenum as (at idle) this effectively only lowers the pressure with which the fuel is being pushed against the pinholed membrane from 47 psi to around 44.
IOW if it is leaking with 44psi behind it, it would do so with 47 too.
Perhaps something else inside the fpr is amiss but the fuel pressure tester will hopefully reveal this.
Good call on observing the fuel wetted hose nonetheless!
You could put some length of clear hose onto the fpr, connect it to the plenum and watch whether fuel actually comes out of the fpr.
Wrt the MAF reading: it measures air mass not fuel mass so it is not surprising that the numbers are unaffected by any fuel from the fpr coming in through the vacuum line or no longer does so with the line removed from the fpr and plugged.
Last edited by hardtailer; 10-12-2022 at 04:14 AM.
10-03-2022, 01:01 PM
