XC70 lumpy idle/lack of power/bad fuel economy nightmare.

[FezMonki]

Hey guys, I have been dealing with an absolute nightmare of a car I suggested to a friend (and regretted it ever since), that has been tormenting me for six months. I am at my wits end and the only reason the car isn't on it's way to a junkyard is all the time and money invested in getting it running right. The car is a late 2000 XC70 with 230k km/140k miles, 2.4T AWD, but for all intents and purposes I'm pretty sure we can consider it a 2001+ MY.

The car idles like ass, seems to lack power for a 200hp car, and has horrifying fuel economy. It has been properly part-cannoned due to my own ineptitude but also it seemed like a good idea to refresh everything I ran into. This is (I think) everything that has been done to it in the last six months:

1. Complete PCV replaced (it was inflating the glove). Confirmed the throttle body is the recall/replaced one.
2. New coolant tank/cap (leaking and ugly).
3. New radiator (leaking from plastic).
4. The two non-return valves on the right of the engine, part of EVAP or w/e, both originals were blowing both ways. And all the tubing replaced.
5. One pierburg valve as it was clicking constantly (the one attached to the filter box). Replacing it fixed the clicking.
6. Temperature sensor and thermostat, as the temperature was always showing 1 mark off center (this fixed it).
7. Sparkplugs (Volvo), new oil (Castrol 5w30), 5 new hella coils, air filter, oil filter, petrol filter.
8. Catalytic converter stolen, welded in a straight pipe (will put a cat back once owner lives in a better neighbourhood as it smells like ass and bad for the planet).
9. Welded in a bung and added second Lambda back. Not happy. Added a spacer with steel wool in it. Still not happy. Popped the ECU open, had the Lambda removed from the firmware. Still not happy (will have to get it removed from someone competent, I only have the tools to read/write but don't know how to remove it myself). Also VIDA still shows the second Lambda, that's why I assume the dude that did it half-assed it (and it throws a code every 3 days after I clear it).
10. Replaced silicon joint between turbo and the pipe from the intercooler, was torn.
11. Gearbox flush with 16 liters of oil (automatic).
12. Suspected VVT intake valve, removed it, doesn't click with 12v. It's the original one and appears to be jammed, can't open and service it as it has a sealed sleeve.
13. As the VVT is sold out everywhere, sourced one from Aliexpress with a Professional Parts Sweden marking on it, and the plug kit.

Now, with the old VVT, the car idled like ass as soon as it got hot. I had disconnected the VVT and am 99% sure it made no difference. Today the new one arrived, I tested it with 12v on the bench and it clicks fine. Soldered in the new plug, put everything back together, and the car idles like ass (disappointment has been a theme for this car so I'm not surprised). But as soon as I disconnect the VVT now, it idles fine.

Which was super confusing. My only theory at the moment is that the old solenoid had seized open, and the mechanic that did the timing belt right before we bought it (an idiot, judging from how he screwed back on the belt/solenoid cover on the left), set the timing based on a camshaft that was retarded (or advanced? I have no idea), so now it runs fine without the solenoid but when it's connected it retards(advances?) it out of expectations again. Is that even possible, would the cam stay adjusted without oil pressure?

Here is a video of the car idling fine, and then like ass when I push the VVT plug in:


Sorry for the bible, thank you if you managed to get this far and I'd appreciate any input. My only other doubt is if the second Lambda could be having this much of an effect on it, as the car also starts running like ass when the engine light comes on, and okay again when I clear it (lasts a couple of days). I'll get around to the Lambda soon, but I don't think this VVT thing is connected. I've been chasing mirrors for months.

[cn90]

You probably have the infamous throttle body issues particular to 2001 and ? 2002 models.
Tons of info in forum...

[FezMonki]

The throttle body on the car has been replaced by Volvo in the past, it's the updated yellow label version, and seems to be working flawlessly with the VVT disconnected tbh. When looking at the value in VIDA, I didn't see any wonky behavior, from what I could tell anyway.

[br0dy519]

I chased this issue on my car for all of 2021 (04 XC70) it ended up being a combination of three things:

1) Vacuum leaks (mostly at the OTE pipe connection to the turbo, one in the line between the charcoal canister and the purge valve)
2) Defective throttle body (Finally threw a code)
3) Defective Purge valve (Likely due to contamination from the aforementioned leak)

It took a long time but I finally solved it. When I called my indie he mentioned something about watching the VVT angle in VIDA, but that's kind of above my paygrade. Likely none of this helps you but just posting here in case anyone has similar issues.

[TisMe]

Sounds like my '01 XC70 issue, matching all the symptoms of your title, except that it wound up being a "sucked valve" on cylinder 3. Zero compression, with all others at 165-170psi. Now if I remove my VVT plug and find a nice idle, I'm going to be thoroughly confused.

I presume it's a waste of everyone's time to ask if you've done a compression test... you seem to have evolved beyond this question, and my correlation is unlikely to equal causation. The simple fact that clearing your code restores performance insinuates that I'm talking just for fun.

[- Pete -]

The car idles like ass, seems to lack power for a 200hp car, and has horrifying fuel economy.

1. Complete PCV replaced (it was inflating the glove). Confirmed the throttle body is the recall/replaced one.
…

4. The two non-return valves on the right of the engine, part of EVAP or w/e, both originals were blowing both ways. And all the tubing replaced.
5. One pierburg valve as it was clicking constantly (the one attached to the filter box). Replacing it fixed the clicking.
…

7. Sparkplugs (Volvo), new oil (Castrol 5w30), 5 new hella coils, air filter, oil filter, petrol filter.
8. Catalytic converter stolen, welded in a straight pipe (will put a cat back once owner lives in a better neighbourhood as it smells like ass and bad for the planet).
9. Welded in a bung and added second Lambda back. Not happy. Added a spacer with steel wool in it. Still not happy. Popped the ECU open, had the Lambda removed from the firmware. Still not happy (will have to get it removed from someone competent, I only have the tools to read/write but don't know how to remove it myself). Also VIDA still shows the second Lambda, that's why I assume the dude that did it half-assed it (and it throws a code every 3 days after I clear it).
…

12. Suspected VVT intake valve, removed it, doesn't click with 12v. It's the original one and appears to be jammed, can't open and service it as it has a sealed sleeve.
13. As the VVT is sold out everywhere, sourced one from Aliexpress with a Professional Parts Sweden marking on it, and the plug kit.

Now, with the old VVT, the car idled like ass as soon as it got hot. I had disconnected the VVT and am 99% sure it made no difference. Today the new one arrived, I tested it with 12v on the bench and it clicks fine. Soldered in the new plug, put everything back together, and the car idles like ass (disappointment has been a theme for this car so I'm not surprised). But as soon as I disconnect the VVT now, it idles fine.

Which was super confusing. My only theory at the moment is that the old solenoid had seized open, and the mechanic that did the timing belt right before we bought it (an idiot, judging from how he screwed back on the belt/solenoid cover on the left), set the timing based on a camshaft that was retarded (or advanced? I have no idea), so now it runs fine without the solenoid but when it's connected it retards(advances?) it out of expectations again. Is that even possible, would the cam stay adjusted without oil pressure?

Here is a video of the car idling fine, and then like ass when I push the VVT plug in:


Sorry for the bible, [snip] but I don't think this VVT thing is connected.

I just want to say thanks for the thorough descriptions of your issues and efforts (and the included video, which triggered my fading memory). A lot of us have felt the same frustrations (maybe rage is a more appropriate adjective) & just when it seems to be too much, something gives.

I have a few questions first, and will follow with a couple ideas/suggestions.

First off, where are you located? I can see your bio, but curious what part of the globe you/this car exist(s) in.

After PCV replacement parts were installed, did vacuum resume? Also is oil psi acceptable? This is measured manually, for the record. It is possible that if the engine was previously/badly “sludged”, the oil pan has been the recipient of some crystalline-type buildup. It is hard to say, without dropping the pan, but if so (if gunked badly), in a way could have contributed to the taking out of the VVT solenoid.

Timing: do you have photos of the timing as it sits now? The 2.4T 01’s (and others) can be misleading & elusive to time correctly.

My theory: the car has been neglected by the previous owner; long oil change intervals (probably low - mediocre oil quality), short drive/heat cycles, etc. This leads to a buildup of unburnt junk that forms into crystals & occludes the various passages through which oil/blowby are supposed to freely pass. You also mentioned the PCV system was replaced, after failing the glove test. These, combined with the failed (likely original) VVT solenoid confirm my suspicions. The mechanic who, from the sounds of it, should be washing dishes or cleaning urinals, has probably set the timing off. The intake cam on these is not monitored by the ECM, the exhaust cam IS. The ECM relies on correct timing to “know” where the intake cam is positioned, based on where the exhaust cam is positioned. If the intake cam is off & the cam phaser (VVT solenoid) is gunked up, you WILL (unfortunately) have an engine that runs as yours is. One thing you didn’t make mention of is any DTC’s. What is showing currently? Do you see a P0014?

I believe you need to 1. Replace that VVT solenoid with a genuine part, 2. Correct, verify, re-verify your timing, 3. (If my suspicions are correct) Perform ridiculously short OCI’s over the next 5-10k miles. For starters (this next 1000ish miles), (using cheap oil), change oil every 300 miles, filter ever other change. Like you mentioned, get a catted downpipe in there too. I don’t think the lambda is what your problem is here.

Edit: I meant to ask why the owner chose to go with Hella coils over Bosch/Volvo since the cost difference is so minimal & also, since nothing but the latter has been proven to withstand the test of time?

[FezMonki]

Thank you all for your precious input.

2) Defective throttle body (Finally threw a code)

I really hope it has nothing to do with that, I'll have to look up how to more thoroughly check this. I want to say it's not a vacuum leak after I molested repeatedly the whole area and replaced most of it.

When I called my indie he mentioned something about watching the VVT angle in VIDA

It did not occur to me that I could check if the VVT was actually working in VIDA as I assumed it was hydraulics moving it only, but I guess the cam sensor is there for a reason. I'll definitely have a look at this.

I presume it's a waste of everyone's time to ask if you've done a compression test...

I... have not actually I'm no mechanic and have just been trying to keep the damn thing together to keep costs down for my mate. I'll take her round to a friend's shop to get that done now that you mentioned it however, at least to rule it out.

The simple fact that clearing your code restores performance insinuates that I'm talking just for fun.

Apologies, I could have worded that better. Basically when the error for the second Lambda comes on, the car starts running like ass all the time and a lot more noticeably. When I clear the code, it goes back to "just" running like ass in the video with the solenoid plugged in. Multiple layers of driving me insane lol.

First off, where are you located? I can see your bio, but curious what part of the globe you/this car exist(s) in.

Me and the bloody thing are both in Italy (Milan), if my English suggests otherwise it's because even though I only spent three years of my life in my native country (Canada), I have aggressively consumed English content my entire life

After PCV replacement parts were installed, did vacuum resume?

Yep, would have pulled the whole glove in if there hadn't been the baffle under the oil cap lol.

Also is oil psi acceptable? This is measured manually, for the record.

This was not measured but will promptly be done as soon as it's in my friend's shop when also being compression tested.

Timing: do you have photos of the timing as it sits now? The 2.4T 01’s (and others) can be misleading & elusive to time correctly.

I do not and am still too much of a donkey/learning to check timing myself, even though replacing the PCV and specifically getting the banjo bolt that goes back into the manifold certainly pushed the bar up for me lol. If the car doesn't go to the shop before I see it again, I'll try and get a picture of that.

My theory: the car has been neglected by the previous owner; long oil change intervals (probably low - mediocre oil quality), short drive/heat cycles, etc. This leads to a buildup of unburnt junk that forms into crystals & occludes the various passages through which oil/blowby are supposed to freely pass. You also mentioned the PCV system was replaced, after failing the glove test. These, combined with the failed (likely original) VVT solenoid confirm my suspicions. The mechanic who, from the sounds of it, should be washing dishes or cleaning urinals, has probably set the timing off. The intake cam on these is not monitored by the ECM, the exhaust cam IS. The ECM relies on correct timing to “know” where the intake cam is positioned, based on where the exhaust cam is positioned. If the intake cam is off & the cam phaser (VVT solenoid) is gunked up, you WILL (unfortunately) have an engine that runs as yours is. One thing you didn’t make mention of is any DTC’s. What is showing currently? Do you see a P0014?

I like your theory, and it would definitely match up. The car had one owner for the longest time and I think they treated it reasonably well, then it went through a slew of owners that probably sold her off due to the issues that were piling up. The oil that came out wasn't excessively shitty but I don't know how long it had been in there. I think I'll just have to get a new timing belt and have someone competent look at it with me this time.

As for DTCs I stupidly didn't take pictures, but in VIDA I was getting:
1. The rear lambda error every three days.
2. Not every time, I'd also get an error related to the VVT (it showed a picture of the VVT and all when opening it). I had initially ignored this, as someone from the Volvo dealership told me it might be triggered by the rear lambda "malfunctioning" (but I'm also starting to think that is not the case).

Since I left the VVT disconnected yesterday, the car now has a P0013 obviously.

I believe you need to 1. Replace that VVT solenoid with a genuine part, 2. Correct, verify, re-verify your timing, 3. (If my suspicions are correct) Perform ridiculously short OCI’s over the next 5-10k miles. For starters (this next 1000ish miles), (using cheap oil), change oil every 300 miles, filter ever other change. Like you mentioned, get a catted downpipe in there too. I don’t think the lambda is what your problem is here.

I basically can't change the VVT at the moment, as this one was the only one in stock on the entire planet from what I could see Volvo told me it will be available "at some point", the big car parts website I use most of the time has 3 models out of stock and so on. Something to do with the global supply crisis I assume. It was also clicking merrily and appears to be the "redesigned" version so I'm happy with it for now (kinda). I will certainly re-do the timing and oil changes however.

Edit: I meant to ask why the owner chose to go with Hella coils over Bosch/Volvo since the cost difference is so minimal & also, since nothing but the latter has been proven to withstand the test of time?

Well to be honest I've been ordering most of the stuff from the aforementioned website as their prices are really competitive, and they didn't have Bosch coils so I just got the Hella ones. I was also blissfully unaware the Bosch ones were in the same price range, I'll definitely go that route when these start looking scabby.

Looks like the todo list is:
1. Check compression.
2. Check oil pressure.
3. Get a new timing belt as I probably shouldn't risk it with this one even if it's six months old, and re-do that.
4. Oil change again for good measure.

This car has made my naughty B204FT 960 look like an angel.

[- Pete -]

Sorry, I didn’t see where you mentioned where you were ordering parts from. Do you have any access to used parts/junkyards? If not, I could keep my eyes out for a 2001 (pretty sure I know where one is) that still has the cam phaser attached. Just saying, to test my theory it makes sense to rule things out, one at a time. I will acquire one or two next time I go to the junkyard, test it on my 2001, and if need be, send it to you (if it checks out).

The VVT solenoid/cam phaser and timing are under equivalent levels of scrutiny (for me) at this point. The cam phaser (and VVT hub) are essentially hydraulic (phaser requires electric pulses, but both are dependent on satisfactory oil psi). If my theory of the engine being sludged aligns and there are passageways that are occluded (partially or fully), it is entirely possible that 1. the solenoid/hub may only be seeing part of the oil psi it wants to see and 2. (Unrelated to oil psi) The PPS solenoid you have could very well be non-functional right out of the box. These ECM’s are very particular about voltage & consumption, inferior parts are frequently detected and discarded. Couple those with the fairly good chance the timing is off and there you go

I ran into almost the exact same issue a few years ago. If you want the read, here it is.

Edit: I never took a video clip of mine idling, but would describe is as a “loping idle”, and had very diminished power also. In your clip where you unplug your VVT solenoid, mine sounded identical.

If your timing belt is of decent brand/quality and isn’t oil soaked there’s nothing foolish about reusing it.

[FezMonki]

Wonderful, I'd happily take a cam phaser even if the timing ends up being off, to have a spare for the future. I had done some reading, and everyone just mentioned swapping it due to noise so I had kind of ruled it out, also was hoping to rule it out because of how expensive the dang thing is from Volvo. There's plenty of these in junkyards, the problem is they are ALL Diesels due to Euro Diesel rush from the 2000s, we actually had to drive a good way to pick up this petrol one (I'm not a big fan of diesels, and also they're starting to clamp down on older ones here, so most can't even drive around anymore).

I had a read on your topic and it seems your car was exactly acting up like this one is now. It did consistently get better with all the maintenance I did in the list above, so it seems all I did was bring it to the point where it matches how yours was behaving.

I'll try and test the oil pressure (will reading from wherever the oil pressure sensor is do, or do I need to hit a specific spot near the solenoid?), check the cam situation through VIDA and timing asap, but it might take ten days before I have the car again. Thank you in the meantime.

[jonesg]

I tested the cam solenoid with Vida, the result was slow actuation possibly due to incorrect oil or low oil pressure.
An oil change fixed it.
Last time I was at the salvage picpull I snipped the plug from a sensor , in future I'll use it for testing ohms and actuation without having to remove it.