Nissan X Trail 2.2 dci won't idle when cold

Ask for and share advice on using the PicoScope kit to fix vehicles here.

Re: Nissan X Trail 2.2 dci won't idle when cold

Postby STC » Tue Sep 06, 2016 8:22 pm

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?


The answer is both, Voltages first to flick the switch / transistor / mosfet gate off and on that converts it to binary and only then can it calculate relationship.

I would like the opportunity to get up close and personal with that vehicle displaying that fault and symptoms. Is that possible ?
STC
Zen Master
Zen Master
 
Posts: 224
Joined: Sun Sep 13, 2015 2:10 am

Re: Nissan X Trail 2.2 dci won't idle when cold

Postby Steve Smith » Fri Sep 09, 2016 8:33 am

Thank you for the posts and support from everyone as the forum proves to be a life line with issues like these.

With regards to the Cam Crank voltage values seen in your original capture Mike, this is because the scope coupling feature set to AC.

AC coupling will reject the DC value and display only the fluctuations (AC signals)

Carry out the same test DC coupled and the voltages should tally with Victors capture.

The coupling status of the capture is visible when opening the psdata file with the scope connected. However, when opening the psdata file without the scope connected the coupling status is only visible in the properties window.

See the image below:

View properties capture.jpg
Properties window will reveal additional data


Just reading the post through, the guide below to measuring Crank Cam correlation will help with evaluation

Assuming your engine is non VVT then we can conclude the relationship between the camshaft and crankshaft signal is a fixed one.

Other than deviation (between Cam and Crank) due to acceleration/deceleration (attributed to load), misfires, chain deflection, gear wear, backlash and chain tension, as near as dam it, the relationship/correlation should not alter.

Start by capturing your Crank and Cam signals on a warm engine at stable idle speed with all load switched off (cooling fans /AC etc.)

Ensure you have enough time span across the screen to capture 2 full engine revolutions (1 full camshaft revolution) Try 20 ms/div and 1MS across the screen.

One crankshaft revolution is often denoted by the missing teeth about the crankshaft Pick –up ring (Either 36 teeth -2 or 60 teeth -2)

Referring to the image below, drag the Rotation rulers to identity 0 and 720 degrees of crankshaft rotation (2 x full crank revolutions)

CAM CRANK CORRELATION MEASUREMENT.jpg
Cam Crank correlation measurement


Choose a reference point on the camshaft after the missing tooth (zero degree Rotation ruler) drag a Time ruler to your chosen camshaft reference point and read the degrees of crankshaft rotation value highlighted in yellow.

Use the same technique from a donor vehicle or a vehicle waveform downloaded from the waveform library to verify cam crank correlation

For excessive cam crank correlation errors where you suspect the chain has jumped one or more teeth, count the number of crankshaft teeth from the zero degree Rotation Ruler to your chosen camshaft reference point.

CAM CRANK CORRELATION MEASUREMENT- COUNT.jpg
Crank teeth counting


A short video can been viewed below

CAM CRANK CORRELATION MEASUREMENT VIDEO.jpg.mp4
Cam crank correlation video
(4.8 MiB) Downloaded 17 times


Good luck with the Nissan and let us know how you get on, take care.......Steve
Steve Smith
Pico Staff Member
Pico Staff Member
 
Posts: 426
Joined: Sun Aug 25, 2013 7:22 am

Re: Nissan X Trail 2.2 dci won't idle when cold

Postby STC » Sat Sep 10, 2016 7:56 pm

Steve

The coupling status of the capture is visible when opening the psdata file with the scope connected. However, when opening the psdata file without the scope connected the coupling status is only visible in the properties window.


Thanks for pointing that out as I rarely have the scope connected unless I am actually Scoping or accessing the Library. I note it also tells us if the file has come from a 2 or 4 channel scope and more.


Mike

You still have a car that will run with the Cam Unplugged.
As per Steve's suggestion scope the Cam & Crank again DC Coupled to dismiss the bad Voltages as a measuring error. Scoped from start to fault as before and then higher revs if that is what it takes to keep it going longer. I'm looking see if either CKP or CMP can be seen/made to fail.

Even with that sorted (DC Coupled) I still have a niggle about both the Cam & Crank Sensor jumping out of sequence as it cuts out. ( The W U U U W above) I cant see that fixed just by coupling the scope to DC, that to me is a fault in the car, at least for now, worthy of further analysis.

Are there any PIDs for Synchronisation, Camshaft, Crankshaft or similar as clues to timing.

Down the line, Viktor's known good waveform suggests that your valve timing is out, which is foolish / difficult to ignore. If that were my job, I would apply a reasonable amount of wishful thinking and be belt & braces on the behaviour of that Cam Sensor & whatever it is looking at first.
STC
Zen Master
Zen Master
 
Posts: 224
Joined: Sun Sep 13, 2015 2:10 am

Re: Nissan X Trail 2.2 dci won't idle when cold

Postby mikeevans » Mon Sep 12, 2016 1:44 pm

The problem is now resolved. New timing chains and gears fitted and all is well. When we removed the upper chain cover, the timing was visibly out due to worn chains.
In future ,the quickest diagnosis will be to disconnect cam sensor, and if it runs well, inspect the timing chain.
Thanks to everyone for your contributions.
Mike
mikeevans
User
User
 
Posts: 17
Joined: Mon Sep 19, 2011 7:18 pm

Previous

Return to Diagnostic discussion

Who is online

Users browsing this forum: No registered users and 1 guest