How do you read timing in VIDA?

[dikidera]

Well this is odd, he had these symptoms originally.

@eric Where did you get this car from originally? Is it a customer of yours? Or did it recently develop this problem where it didnt have it before?

I would still try to set the timing again, but also do the crankshaft. And remember to do two full crankshaft rotations to verify no piston to valve contact. Although maybe it already did before you even started.

[vtl]

With VIDA connected to the car, rev up slowly above 1500-2000 RPM and make a screenshot of adaptation angles. Maybe needs to be done on the go, under real load.

[erikv11]

@ dikidera:
This is my own car, purchased about 6 months ago.
The previous owner had it serviced regularly at a reputable shop.
First the car seemed to run well, then started to chug over the last month.
Yes the crank is on the mark I was certain.
I just checked timing again and the marks (including the crank) all seem perfect. However the exhaust cam could be off relative to the exhaust VVT hub, of course.

With VIDA connected to the car, rev up slowly above 1500-2000 RPM and make a screenshot of adaptation angles. Maybe needs to be done on the go, under real load.

Or maybe it is shifting angle? The adaptation angle is unchanging regardless of revs. Each time I start the engine I get slightly different value but it then stays completely unchanged unless I start the engine again.

Here is a pair of screenshots, low and high rpm, note Engine Speed is in the pics. At the higher rpm there was some clear vibration from the engine chugging.

pair 1, low RPM

IMG_4381.jpeg (897.81 KiB) Viewed 875 times

pair 1, high RPM

IMG_4382.jpeg (1.01 MiB) Viewed 875 times

pair 2, low RPM

IMG_4384.jpeg (931.17 KiB) Viewed 875 times

pair 2, high RPM

IMG_4386.jpeg (958.88 KiB) Viewed 875 times

Exhaust is somehow off by about a tooth, too far advanced? I was very careful to rotate VVT clockwise before timing it but maybe I disturbed it when I tightened down the center torx.

[vtl]

Or maybe it is shifting angle? The adaptation angle is unchanging regardless of revs. Each time I start the engine I get slightly different value but it then stays completely unchanged unless I start the engine again.

Adaptation is tested the first time the engine is reaching 1500 RPM after start.

[erikv11]

Adaptation is tested the first time the engine is reaching 1500 RPM after start.

Thanks again for the explanation.

I have checked many times in VIDA now, adaptation is usually between 0 and -2.5, farthest off I saw it was -3.6, so seems imperfect but good.

Also ran the VVT test in VIDA several times, and both VVTs look great, never off my more than 1 degree.

All of this was done in the driveway, not under load. No codes.

I interpret timing is fine and so I did not, in the end, take off the timing belt and re-check the camshafts with the tool. Instead I will move on to other sources of the chug. Anyone disagree, could it still be timing issue? Something else to check?

Thinking I will drive it easy this week and hope for a code. May even take it to the Indy if I can't find anything, we'll see.

[vtl]

I would check the valve clearance next. My understanding the tappets are softer than the valves and the camshafts, so they wear quicker than valve seat and face, so the valve clearance does not need to be adjusted if you're okay with a bit worse engine performance. However, if the cylinder head warps in the middle, it reduces valve clearance in the middle, and the valves may not seal properly anymore.

Another potential problem could be the back of the lobes covered with hard oil deposits. I don't know if these deposits are hard enough to prevent valves from closing properly, though. Example from the donor engine w/ 220k miles I took apart:

3.jpg (196.89 KiB) Viewed 793 times

That's my engine with burnt valve. It was much cleaner:

1.jpg (328.55 KiB) Viewed 793 times

No head warpage, and I actually measured all tappets to be worn. Had to buy 16 new tappets to bring the valve clearance to spec.

Untitled.png (506.49 KiB) Viewed 793 times

[abscate]

4 degrees of shifting angle means you are spot on , tooth wise. I would look elsewhere for the chug. One tooth off is about 8 degrees cam angle , (or 16-17 degrees crank angle reported in VIDA) if the p2 is the same teeth ration as p80, which I think is true

Gory details

viewtopic.php?t=93792&hilit=Cam+flank+angle

[jonesg]

" I was very careful to rotate VVT clockwise before timing it but maybe I disturbed it when I tightened down the center torx."

I tensioned the timing belt to hold the cam hubs before cinching the center bolt.

At this point I'd look at compression , fuel delivery, then ignition.
compression test first so you don't waste time chasing ghosts.
Fuel pressure at key on, again after it sits 20 minutes and pump duty cycle after a run with chugging.

[erikv11]

Thanks for the posts I appreciate the help.

At this time I am not keen to check valve clearances will mull it over ...

At this point I'd look at compression , fuel delivery, then ignition.
compression test first so you don't waste time chasing ghosts.
Fuel pressure at key on, again after it sits 20 minutes and pump duty cycle after a run with chugging.

compression: 135-135-130-137.5-135
that was on a cool engine: ran about 5 minutes. It's war, today 62 ˚F.
injectors all unplugged for the test
NOTE: that sets injector codes that must be reset in VIDA before the engine will start back up when you put it all together!

fuel pressure, key on 38 psi
fuel pressure, cranking on 55 psi
fuel pressure 20 minutes later I can't check, my gauge has a slow leak where it attaches to the Schrader valve.
fuel pump replaced with Bosch when I got the car, about 5k ago. dead fuel pump is why they were selling.
fuel pump wire harness to PEM: new Volvo about 5k ago (with fuel pump job)
fuel pressure sensor: new Bosch about 5k ago (with fuel pump job)
PEM: original

plugs: Volvo branded by PO (shop), all 0.029, light tan deposits or white, looking good.
coil packs: about 200 miles ago I swapped in the nearly new (less than 10k) Bosch coils from my other XC70, to see if they helped with the chugging or fuel economy. no change

I drove by the shop too and he said "we have struggled with those dual VVT Volvos, sometimes had a hard time getting them right, I will give the timing a look otherwise no suggestions offhand what else it could be."

Right now I have an appointment with them for 10 days from now (they are booked) so I have 10 days to figure it out. I'll keep driving it looking for a code.

More suggestions/follow up?

[erikv11]

Anyone, how do you "test fuel pump duty cycle after a run with chugging?"

For the record it always chugs now, all engine speeds. It's subtle but unmistakeable. Maybe more noticeable under load. Performance is also down a bit to match the chug.