2001 v70 2.4t misfire issues

naonin · Post by **naonin** » 26 Jan 2015, 16:18

I've done a ton of stuff already and I'm at a complete loss of where to go next. The car will start but absolutely no power, it dies under load. So let me fill you guys in what I've done.

I've pretty much ruled out fuel. Injectors have solid pressure, spraying evenly (tested by eye pulling rack and cranking). Changing around injectors does nothing.

Great spark, new coils, plugs.

New ECM, plus it has the upgrade flash.

I reset the timing belt because I had another mechanic do the timing belt and within a month or two it started running shotty (I feared he didn't set the vvt correctly). I did it three times and even messed up on a few setups (crank was one tooth advanced, lesson learned). Still didn't fix things. It didn't even start when I got everything back to the marks and it DID start when the crank was advanced one tooth. Disabled the vvt solenoid and cranked it again and it fired, but still getting the code for a misfire. Likely not timing (I have considered retarding the exhaust cam a few degrees but I don't think that'd be the source of misfire).

Today I did a leakdown test. Cylinder 3, the one throwing the code and the one that burnt through a coil, had the best compression, 8% leakdown(!!). Cylinders 4 + 5 were the worst at ~50%, a fair bit of air leaking through the intake side. 1 + 2 were at ~20%, fairly even loss, maybe more through intake.

Now what in the world does this mean?! Why is cylinder 3 throwing the misfire code with everything seeming okay? Low compression on 4+5, is the computer trying to compensate because the drastic difference? Do I need a valve job? Anybody have experience with the only good cylinder misfiring?

Post by **oragex** » 27 Jan 2015, 09:40

what spark plugs and what is their gap?

draser · Post by **draser** » 27 Jan 2015, 11:01

You'd need to address compression issues from leakdown test. Since multiple cylinders seem to leak I'd look into timing the cams again, since it's more likely they're off a bit. I'd 2-check marks on sprokets and crank along with opening up the back end of camshafts to confirm slots are both horizontal. Do you know if sprokets were removed?

naonin · Post by **naonin** » 27 Jan 2015, 11:19

I don't know if the other guy removed the sprockets. I don't think so because they would've been cleaned.

This most recent time that I set the timing I did rotate the crank two times by hand and the cams came back to horizontal. Is two rotations enough or should I be checking it again?

Do I need to do anything else besides unplugging the vvt solenoid if I want to bypass that just for testing sake?

draser · Post by **draser** » 27 Jan 2015, 11:50

If back slots are horizontal and front marks line up you're good as far as timing. But thats bad news as valves don't close fully. And if you get it somehow to run it'll burn valves. I'd consider pulling the head. But before I'd pour 5-6 drops of oil in plug hole and do a compression test to see if results match leakdown's.

naonin · Post by **naonin** » 27 Jan 2015, 12:47

With the spark plugs removed (all gaps were mostly .030 give or take .001, and one which was .038... I don't know what happened there) I checked tdc for cylinder 1 at the top of the marks. When I found tdc, all gears were advanced one tooth, including the crank. Also, moving to the marks, my exhaust cam isn't parallel, it's advanced a bit. I'll redo the timing again with the vvt solenoid unplugged the whole time.

I know Volvo doesn't exactly do tdc timing but is this an issue?

draser · Post by **draser** » 27 Jan 2015, 13:18

Can't do TDC timing unless you use a timing wheel, reason is ignition happens few degrees before. So you will be off the marks. Why can't you time using timing marks?

villagepc · Post by **villagepc** » 27 Jan 2015, 13:42

triple check your timing. my car acted the same way when my car had the exhaust cam off 2 teeth (intake and crank were ok)

Usually when reinstalling the timing belt, that's when it "jumps" teeth - when the slack is taken out of the belt, everything tends to rotate to compensate where the belt's teeth are lining up.

I haven't monkied with a VVT engine - so I can't help there - only reinforce that your timing sounds way off -

naonin · Post by **naonin** » 27 Jan 2015, 14:25

Okay, that makes sense about TDC.

Did a reset on the timing. Here's what I did exactly so you guys can check if I'm not making a mistake somewhere along the way.

1. Loosen timing belt

2. Straightened exhaust cam to horizontal. Locked cams with locking tool.

3. Moved crank slightly CCW so the belt would set on the correct tooth.

4. Moved exhaust vvt pulley clockwise to limit, the mark lines up perfectly.

5. Put on belt, tensioned, rotated two times, everything lined up.

6. Rotated 90 degrees clockwise and then back to the marks. The exhaust cam was advanced. I figure it should be because that's the vvt spring doing it's thing.

7. Rotated another two full rotations and everything was lined up and cams were horizontal again.

Seems like that should be fine right?

Did another leakdown test, (I made a mistake in my OP, I numbered the cylinders backwards, derp), cylinder 1 still shows high leakage.

So to clarify, cylinder 3 is throwing a misfire code. It has very little leakage but lots of carbon buildup. Cylinders 1+2 have the most leakage, no buildup, never any misfire codes. Occasionally cylinder 5 would throw a misfire code also, but that one only had ~20% leakage.

I'm going to take off the valve cover and do more leakdown testing. It's looking more and more like valve damage. I'll find out shortly I guess, maybe I'll see something.

Thank you everyone for your input so far.

naonin · Post by **naonin** » 03 Feb 2015, 21:13

Alright bad news. I brought the head to a machine shop, the guy told me the head is cracked on each exhaust valve. So that head is scrap.

I'll end up getting a new engine I think. By the time I get a head gasket kit, bolts, no promise the valves on another head are solid, no promise the heat that caused the crack didn't impact the pistons.

Thanks again.