In this post I'm looking for a knowledgeable second opinion to my own diagnosis, which I won't describe here at the moment. I've been connected with the automotive industry for 50+years so know a bit beyond the basics of diagnostics but this issue on my wifes car has me really stumped. Been trying to sort it for some weeks and I've even conjured up a few new unmentionable expletives!!
Long story cut short is as follows. The car is 2007, owned from new and has 61000 miles registered. In 2021 I felt it was time for a timing belt change and as I had a lot of other projects going on at the time I put the car in to a local garage with a good reputation for a cambelt, idler, tensioner and water pump replacement. Job finished and the car ran well for about 4/5 months.
Then it started to cut out occasionally whilst driving and sometimes it would start and immediately cut out. After a few minutes it would start again and drive for some days or even weeks. Gradually this got more frequent so I decided to investigate it myself.
Out came Lexia and it showed many speed errors in the log - mainly PO339, so an inconsistent camsheft/crankshaft timing. First thing I checked after removing the timing covers was that the timing belt was still intact with no missing teeth. Next was the a visual inspection of the reluctor ring. BINGO! quite a few of the magneic sections on the outer circumference of the reluctor ring were gone. I then inspected the crank sensor and found that there were marks on it associated with rubbing on the reluctor ring. So my analysis was that when the cambelt job had been done some months previously the sensor had been fitted with insufficient air gap between it and the reluctor ring resulting in rubbing and damage to the reluctor ring magnets.
I subsequently found when fitting a new reluctor ring and crank sensor that indeed there was sufficient tolerance in the sensor fixing point to allow it to rub on the ring. I fitted the new sensor with a 2mm air gap.
Also since it was dismantled to replace the reluctor ring I fitted a new cambelt. Crank locked, camshaft locked and fuel pump locked. Turned six revs clockwise by hand, then again and again to be sure. All lined up and lock pins could be inserted in their relevant positions.
I also noticed that when priming the fuel system there was air in the system so replaced the fuel filter and the fuel lines which came as a fuel line harness.
Now my real issue. Started the engine and it idles real sweet and smooth at 768 rpm. Gentle increase in rervs and at 900/920 prm the is a sudden clack/clack/clack noise and the engine misfires. Release the acelerator and it's back to very smooth idling. Sound at the exhaust is completely normal with no indication of misfire.
I removed the timing covers and the crank/cam/fuel pump holes all align and lock in place correctly. So it's not a timing belt issue!
Lexia shows fault code PO104 - Flow meter fault. This apparently relates to the Mass Air Flow sensor! What??
Lexia also shows PO238 - Turbo Pressure fault!!
Lexia also shows PO 339 engine speed (crank/cam) mismatch. Which I think is down to the clack/clack and misfire occurance.
So, I'm at a loss. I'm thinking possibly a fuel pressure issue caused by air in the high pressure system but with the new low pressure lines and no sign of air in that low pressure system I can't fathom how that could be.
All informed suggestions are welcome and thanks for taking the time to read this lengthy post
:)
