Nissan X Trail 2.2 dci won't idle when cold

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Nissan X Trail 2.2 dci won't idle when cold

Postby mikeevans » Thu Sep 01, 2016 9:10 pm

Hi , I have a difficult problem with a 2007 Nissan X Trail 2.2 DCi. Starts and runs well with no performance issues/ smoke etc
The problem is that when it is cold it will barely idle, If the revs are kept at 1000 or above it keeps running, let the revs drop, it stops after a few seconds.

When the engine is fully warmed up and hot, it will idle and run ok at about 725rpm. Let it stand for about an hour and it's back to cutting out. When it stops, it is instant, as if the ign. has been switched off. Restarts ok. Fitted alternative gravity fuel tank but no change.

No EML and no stored codes. Fuel pressure is good, up to about 280 bar instantly.When the engine stops, fuel pressure is good, increases a little immediately afterwards then gradually fades off over about 10 secs.
Relay supply to ECU is good and present when engine stopped. Spoke to BBA reman who suggested a check on throttle body. They found a fault with it , repaired and refit with no change.

Not sure where to go with this now,puzzled why it has such a severe fault with no codes or EML. Seems to be temperature related, dynamic data appears to be ok , coolant/fuel temps etc.
Considered cam v crank signals but having seen some samples on the web I am still not able to interpret these properly and am not confident enough with this. Possible ECU Fault? Any help will be much appreciated.
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby volrem » Fri Sep 02, 2016 4:32 am

Measure cam and crank to check for streched chain ( i think it has chain).
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby victor2k » Fri Sep 02, 2016 3:53 pm

Hello,
Can be the chain elongation or the pump bolts broken... the engine work bad and more white smoke :D
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby mikeevans » Fri Sep 02, 2016 4:20 pm

No excessive smoke at all. Disconnected cam sensor and now idles ok.
We now suspect timing chain wear and have scoped the cam and crank. I do not know how to interpret this and fail to see the relationship between the two. I will try and post it on the forum and will welcome any advice from the experts.
It would be great to be able to diagnose this fault with confidence by looking at the scope sample.
I have found several examples of cam vs crank samples and I am eager to learn how to interpret them.
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby victor2k » Sun Sep 04, 2016 6:03 am

Hello,
Here you will find a good CKP vs CMP signals
Regards
Attachments
Nissan X Trail 2.2d CKP vs CMP idle good .psdata
(99.6 KiB) Downloaded 32 times
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby mikeevans » Mon Sep 05, 2016 10:21 am

I have managed to get a reasonable waveform from Ign. on through to engine stopping. Advice on interpreting this will be appreciated
Mike
Attachments
Nissan_X-Trail_2007_Diesel_Cam v Crank 2.psdata
(647.8 KiB) Downloaded 25 times
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby STC » Mon Sep 05, 2016 1:16 pm

Happy Days - the fault is in there :D :D - Just got to fix it now. :(

First thing to do is look at the MINUS Voltages on both your Crank & Cam. I would expect them both to be dancing between 0v & 5v. Viktors' capture confirms that!
Is that a bad Earth, 5v Reference Circuit or the Scope not connected / earthed properly ?

Xtrail 1.jpg

Xtrail 2.jpg

Xtrail 3.jpg


It is difficult to work out which one threw its toys out first, I would say the Crank dipped out first yet
Disconnected cam sensor and now idles ok.
and that Cam signal is clearly wrong too. Both faulty at the same time ??? All of which is immaterial while those Voltages are wrong.

Add to that the suspected 10 degrees timing drift.

At least you have a direction now with which you can move forwards.
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby mikeevans » Tue Sep 06, 2016 8:45 am

Thanks STC for your detailed reply. I will have to study it more as I am still unsure where to start counting teeth etc. and cam/crank signal relationship.
I have captured the waveform for the 3 wires on the crank sensor. This was taken with cam disconnected which allowed it to idle perfectly giving a steady reading.
What should I look for on channel B ?
I see that the voltage on channel A is now correct. I can do a cam sensor check (cranking) with the crank disconnected to see if the voltage is correct. If so , could the 10 deg. timing error be the cause of the neg. voltage readings in some way?
Attachments
Nissan_X-Trail_2007_DieselWith cam disconnected.psdata
(200.66 KiB) Downloaded 10 times
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby STC » Tue Sep 06, 2016 6:48 pm

That capture of the Crank is "text book" Correct voltages. The 5 little bits of interference are the injectors firing and the ECU is well educated to ignore that. In fact it cannot see it.

What you really need to do is take that capture as the fault occurs. I'm guessing it wont with the CMP unplugged ? Is that correct.

What should I look for on channel B ?


Imagine if you were to remove the Relucter toothed wheel that the Crank CKP looks at, removed the centre and Ironed it out flat so it looked like the Rack in a Rack and Pinion Steering Rack.
Rack and Pinion Delete.gif
Rack and Pinion Delete.gif (5.17 KiB) Viewed 115 times

Note that I have altered the image to show the missing teeth. That is what it should look like, or a mirror image and it does.

Sorry, but im going to bang on about the Minus Voltages again.

Two vital questions, clues if you prefer, again I refer to the wrong Voltages in your initial capture
1. How did you correct the Voltage Issue ?
2. Was it a measuring error or has disconnecting the CMP that bought the voltages back ?

The 10 degree issue can be left on the back burner for now, we dont want to be sitting on the is it Mechanical or is it Electrical Fence. That will mess with our mental health & increase consumption of the Golden Nectar.
Let us not lose sight of the fact that it runs and idles with CMP out of the equation.

I have sent you a PM.
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Re: Nissan X Trail 2.2 dci won't idle when cold

Postby mikeevans » Tue Sep 06, 2016 7:39 pm

Thanks again for your reply.
The Crank signal voltage was corrected simply by removing the Cam sensor connection. In doing so it corrected the voltage and also allowed the engine to idle properly.

Out of interest, we disconnected the crank sensor and scoped the cam signal assuming that we would get a waveform at cranking speed. To our surprise, the engine started and idled perfectly, and also corrected the cam signal voltage in the same way,as the crank signal.

When both sensors are connected, the voltages return to -3 to + 1 etc and engine will not idle.
Is it important for the voltage to read between 0 and 5 v or is the ECU more interested in the cam /crank relationship?

Just to reiterate the original fault,

Car starts and revs to max revs with no performance issues.

Engine will not idle, cuts out almost instantly below 1200rpm

Improves when fully warmed up,but when switched off and left for an hour or so, fault returns.

No EML or stored codes.

We could be missing something painfully obvious ??

My head is beginning to hurt so lets see what tomorrow brings :)
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