MAF sensor question

what fuel pressure have you got?

Both actual and target rail pressures are varying with the idle speed, as one might expect, but it's around 30MPa. Again if the revs are raised to 1000rpm it's then rock solid. Should have mentioned that a known working MAF from an identical vehicle behaves exactly the same when fitted to this one. Reference voltage is solid on the 'scope...

I was hoping it might trigger an "oh it's that" response, as this thing has a long and sorry history and just about anything that can be checked or changed, has been. Including at various points over the last couple of years, complete engine (incl pump and rail), injectors and ECM. It's better than when the story began, at least it starts now without needing to flatten two batteries and empty half a can of easy start and it behaves itself impeccably when hot. It's clearly got some obscure fault with the vehicle itself :( That or it's haunted.

Is this a 2.0 in a Transit ????

Tim..

On 18/06/2015 17:57, Tim Is this a 2.0 in a Transit ????

It's in an Xtrail 2.2TDci. Although it's probably a rather large red herring to the actual problem of poor starting*. It is the only reading that doesn't tie in with what it should be though, every other voltage and waveform is spot on. As indeed is this one if the revs are raised slightly.

*Yeah, I've posted about this thing before, it's had a whole engine swap since then... Well not poor starting, as such, because it does actually *start* easily enough now, it just chucks grey smoke and unburnt diesel out the back and the idle is all over the place. Until it gets hot. Then it's fine. It feels like it's timing, but the marks line up where they should and the compressions are good. Could be injectors, though they've been tested by a diesel injection specialist and pronounced ok and they are a bit pricey to just change on the off chance :(

tight valve clearances or damaged valves are my first thought hearing that description. in the past I have sometimes found that a tiny bit of advance beyond the normal markings helped with diesels that were lumpy when cold, but I don't suppose that is possible on the modern stuff

If you dropped an entire engine in to replace a 'broken' one, direct from another car as-was, then you'll need to have the ECU adapted for the suction valve calibration for the 'new' engine. Dealer only or someone with the genuine Nissan Consult tool.

That will correct the issue. Lucky that it runs at all, usually they wont.

Tim..

On 19/06/2015 12:37, Tim

Unfortunately not the issue in this case, already did that (with a Vantage Pro). Shame that tool can't code the injectors as well, because that didn't help either, just made the local Nissan dealer a few £ richer :(

By way of background, the "new" engine, which has much less mileage on it, ran ok (cold) in the "other" vehicle, (which was written off) but in this one it exhibits the same symptoms as the previous one did when cold, albeit not as badly. At least this one runs nicely when hot, unlike the old one...

I'm now thinking about an ECM issue*, though I've been assured by more than one ECU specialist that since it runs fine when it's hot and all the (other) signals are correct, that this is "extremely unlikely" and that it must be "a mechanical issue"... I have been made aware of the rear cam sprocket differences, but this engine is the same year and should have the correct one fitted. Will pull it apart and check though.

*Rather than the ECM being "faulty", I'm wondering if there is a component which is a mismatch for the software, though given the symptoms are much the same, with different parts, it seems somewhat unlikely.

Can you tell us the old & new engine codes (YD22 DDTI xxx) , the yr of the xtrail (since they changed the management) and if the ECU is running the latest firmware (since there was 8 if not more revisions)

Have you checked the valve clearances ? Also check for timing chain stretch , again common.

ECU's indeed do usually work, or not work, or fail when hot and loose / ignore signals (GM 5v references going missing for instance)

After that we'll need to look at live data more closely and check that you still dont have a s/v fault.

Tim..

>

PS, what diagnostic work have you done with the EGR valve?

Tim..

>

Both are 56 Euro IV spec YD22 DDti, 4WD,6spd manual. Neither have DPF or throttle bodies, both have oxidation catalysts but no lamba sensors.

Nissan claim there are no updates for the ECM according to their database.

Valve clearances have been checked, compressions are all even at around

400psi It is looking like a stretched chain though.

The engine came with a recently replaced, new genuine one :)