2005 3.0 BMK TDI - Ongoing Investigation...

**edwardsj** · 27-11-2014,06:16 PM

Evening all, thought I'd post an update on my fault hunt - trying to resolve surging around 2000rpm, smoking when accelerating, general poor mpg, general lack of power. But runs "dandy" with the maf disconnected in default mode. Having already swapped MAFs and sanity cheked the readings, this has been disregarded, and I've pressure tested the inlet system to check for perished hoses, cracked ICs, etc. Found blocked egr nozzle (thanks Gupsterg!), which I cleaned out. It seriously reduced the maf readings, brought them on-spec at idle, but problems still remain.

Wanting to rule out the egr, I removed it for inspection. It was actually curiously clean inside, the smallest film of soot/oil fouling - I somehow thought it was gonna be much worse.. tested operation by applying vacuum, and could see that the valve cracked at about 200mmHg, and was fully open at a little over 420mHg. Operated smoothly enough, closed willingly and proportionally to vac pressure as you'd expect. Obviously can't guarantee what it operates like when hot, but it looked A OK. Wasn't that easy to remove actually - don't know if this is unique to BMKs, but the egr was held on with two spline-head set screws. One I needed to use a 1/4" socket as a bit holder to access, because there was no clearance, and the right sized extension bar to be able to use a ratchet. Thought it was gonna shear off one of the 1/4" drive sections.. and that was the easy one. The lower fixing required a knuckle joint in the equation, which made torque harder to transmit, and keep applied squarely..needed to use a spanner for extra leverage on the ratchet, but it came off. Fair play to other posters who found this removal easy - I normally do OK, but thought this one was unexpectedly awkward!

Obviously the manifold top section had to come off, here's what I could see in the lower sections..
left bank.jpg 100_1505.jpg

Left side a little worse than the right, but I'm not too worried about this. I might be wrong to be dismissive - somebody tell me if this requires urgent attention =]

Also, on the right, I found some pooled red stuff ..

100_1513.jpg

And I have no idea what this is. Perhaps an old coolant leak that wasn't properly cleaned up after. I'm not loosing any as far as I know..

But not finding anything obviously wrong with the egr, I put it back on and did some drive testing. With the egr forced shut (control hose blanked), the car drove the same as ever. With it forced open, by applying manual vac pressure and trapping it with a valve, the car drove very differently indeed! Struggled to accelerate, no power at all, no pickup, undriveable! Now I know what a stuck open egr feels like! I partly releived some pressure (but left the egr cracked open) and was able to drive it back. By similar method, I tried forcing open/closed the cooling valve (behind the main egr), and test drove in both positions. No difference - wasn't sure what I was expecting.. But from this I'm concluding that the egr, at least the main valve, is doing what it's supposed to.

As silly as this may seem, I tried running with the throttle body valve forced open, as I notice that it is left fully open in default running. The car actually had noticeably less power, so assume that this is doing it's job also. Didn't/haven't yet tried disconnecting the link rods on the manifold runners (to leave open) to see if that does anything..

Changed out the map sensor today. Noticed that it does report back diffrently. At stop, it reports atmospheric pressure (today 100mPa), at idle just about (101/2). When driving, now builds upto 120ish and holds before surge, where it was 130ish before. Don't even think it's related to this sensor, but the intake temp seems to be a little higher also - it was never more than 4/5 degrees above ambient before, whereas within a few minutes of running i'm seeing 7 above.. this might be red herring tho. Took it for a quick test drive, and it did seem to smoke a little less. Still surges at the same engine RPM, takes a little longer to build up there, but no immediate plumes of smoke out the back, where as before there was a trail. On the return part, I tried to make it smoke by going WOT during the build-up to the surge, and I only a little smoke out the back was apparant this time.. Will confirm this with a test drive later by doing a regular trip - I know were it smokes..

Even if the smoking is partly cured, the surging problem remains.

One observation I have made is that when running with the maf disconnected, I still seem to register turbo boost. And in fact, it's the same boost pressure-to-engine rpm profile as I see when running with the maf in place. I thought that running in default mode should disable the turbo, yet I am definitly getting a pressure! Perhaps this only applies to vacuum operated turbos, not electric ones. Or is there some default position that the turbo goes into in default mode ? I'm wondering if the turbo mech isn't physically stuck in one operating position - specifically a position which generates boost at around the 2000rpm mark, and not much before.. I think I need to remove the turbo, but it doesn't look easy.. Reviewed the elsawin procedure, but it never tells you the full story =]

Also got some glow plugs which need doing, numbers 2 and 4. These look to be the most difficult ones to access too, what I think is #2 is below the left bank fuel rail feed pipe, and #4, at the back of the right bank, is occluded by lots of hoses/wires. Elsawin doesn't say about removing pipes or manifolds to do this job - but access does not look easy for most plugs...

Anyway, the work continues, I'm sure I'll bottom this one out in the end - one way or the other! Starting to run out of steam for car work though - cold weather isn't helping.. I'm still aware that it's been suggested before that one or more of my injectors might be failing, I'm still treating this as last resort! If I do manage to get the turbo off and find nothing wrong with it, I might have to give up and take it into a garage for diagnostics =/

**edwardsj** · 28-11-2014,01:13 PM