Martin Canyi

Hello my friends, I´m from Slovak Republic from center of Europe.
I have small garage - car service for friends.

Now I have new project (not my car) - first time 350Z (no one wants to repair it).

Problem: after car crash at front side (crashed: front bumper, right frame, lights, coolers) did another car service fix front side of this car and for a short time engine operating without any problems.
But now is engine unstable - after starting is problem to get stable rpm. 2 times will engine turn off. At the third start engine works, but with unstable rpm. After engine warming is situation the same always.

- I have checked cables for ignition - OK
- spark plugs - new Denso
- ignition coils - OK
- nozzles - OK
- diagnostic with nissan data scan - OK
- air leak at airstroke - OK

So I had to check a leak at suction valves during compression. I have flood them with petrol and this is the result:

At all suction valves are the results very similar. My next step will be a dissassembly of timing cover and timing checking.
Do you think that a problem with leaking at suction valves can be caused by damaged timing during car crash?

Thank you for any ideas.
Best regards Martin

calvin.w

Best case is you could have a dirty MAF sensor.
Since you checked everything else, worst case is your timing is off, timing chain could be stretched, timing tensioner(s) could be bad. It's a long project but it's worth looking into

calvin.w

Also make sure all the connections are good. Especially the sensors

calvin.w

Before doing what I just said, clean the MAF sensors and also make sure they have power. Since you have an HR, I'm more familiar with this than the other engines.
if it isn't the MAF sensors, do a compression test. You can get a compression test kit for a reasonable price and YouTube will show you how to perform the test.
if the compression is ok, check the timing. If the timing was off while the engine was running, you may have bent the valve(s). Then it will be expensive. But if you're lucky like I was once before, then you can reset the timing and fire it right up!
Keep us updated and ask questions!

Martin Canyi

Thank you Calvin,
both Maf sensors are cleaned with Protec Maf cleaner. I cleaned all motor electric connectors too. If I dissconnect Maf sensors during started motor, rpm go increased. On both Maf sensors is reaction the same.

I did make a compression test of course. I have my own compression tester, similar to tester at the picture:


I use the left tool - you holding tester in your hand... I tested with this way many cars.
At cylinders 1,2,4,6 is pressure 150-155 psi (10,3 - 10,7 bar)
but at cylinders 3 and 5 I cant hold my hand. The tester is allways fired off from sparkplug hole...
So my opinion is that there is something with timing, with valves or with pistons rings...
What do you think? Thank you!

calvin.w

From here I'd rather ask @dkmura since he knows more.
I really know the basics but from there it's just guessing for me.
​​​​​@MicVelo might have an answer

dkmura

iTrader: (64)

The first thing to do is ask a few more questions about the crash. We assume this Z ran perfectly before that time. You mention: "...front bumper, right frame, lights, coolers" were replaced, Can you provide more detail on exactly what was replaced besides the right side bumper impact (aluminum) bar, headlight and radiator? Was there damage to the RS frame rail? If so, the RS airbox, connections and components would have been impacted as well. Provide some additional details about the crash itself (speed at impact, where/what was hit, etc.), so we can evaluate whether the front cover and other timing components could have been impacted.

BTW- it's difficult to offer any kind of educated guesses without seeing the car, repair and evaluating the car in person. Pics are helpful, but let's be real- these kind of questions are almost impossible to do anything but offer wild-*** guesses.

Martin Canyi

Hello, thank you dkmura. Yes I know what you mean. I have similar opinion at this thing.
I still waiting for more info and photos from car owner about his car crash.

During this time I had dissassembed front aluminium engine cover.
After long rotating ) I have found right timing possition.

But I think that the timing is not at the right possition.
But I need help from you please with checking if I have right.

Here is photo of crankshaft. Is that top dead center please?




The yellow marks at camshaft are at right place too. But they are beside from marks at engine block.
What do you think about this please?






At the right side I have found at short chain bad tensioner.
Please see the video file.
All marks at chanis are at right places. So is there bad main tensioner or is there problem with variable valve timing?
Thank you for your ideas.
Martin

dkmura

iTrader: (64)

Martin- even on my 350Z racecar, I haven't had to do any timing work on the HR engine. For your questions on timing marks, I'd refer to the factory FSM. Here's a link to USDM manuals that may help: https://www.nicoclub.com/nissan-service-manuals

Has your customer given you any details on his/her shunt? That should provide more insight into the problem(s). Nissan engines like the VQ35HR are precision built powerplants and it's rare for them to jump time unless some traumatic event occurred.

Martin Canyi

Thank you dkmura. I will try to find something at nicoclub.com.

I have now some photos from the car crash.
Damaged und replaced engine parts: steering pump, oil pressure sensor

calvin.w

Thank goodness for the crash bar, right?
then again, this could have been a whole engine swap so definitely could've been worst