2009 XC90 V8 misfires and shudder

ozxc90v8 · Post by **ozxc90v8** » 24 Jul 2021, 22:24

Hi everyone,
I recently purchased a 2009 XC90 V8. It has random misfire codes,
And auto shudder.
The engine itself seems fairly smooth and only shakes about 5mm or so at idle.
The annoying things are the misfire codes and shudder. (especially on TC lock up),
It was apparently also recently flushed with Penrite Transmission fluid,
Which I am not sure is any good or not.
With no acceleration it is a bit jerky in the way it moves,
So in D with no accelerator, it just seems a bit rough in the way it starts to move,
Although with some acceleration applied it takes off fairly quick.

It pulls an incredible amount of vacuum at idle sucking the PCV hose into a flat squished position,
And if the oil cap is removed while running sucks it down noticeably,
Although it can still be removed,
Then produces a suction airy sound.

The last owner replaced the PCV apparently,
Had Rocker cover gaskets done and it's clear the intake manifold has been off,
As a couple of the allen key bolts are missing.

I have a generic Scan Tool and wanted to know if they read everything correctly,
As it stated the "Spark Advance" varies from -1.5 to +20 or so degrees at idle,
Which seems odd unless the knock sensors are freaking out on the misfires.

Some of the info from the Scan Tool is:
FPR 375-380KPA
MAP 35-36KPA (44 LAST NIGHT)
IDLE 650-700
SPARK ADVANCE -1 TO +26DEG
MAF 5.36-5.91 (7.68 LAST NIGHT)
TP 13.7 ( 14.9% LAST NIGHT)
0S12 0.885V
0S22 0.900V
SHRTFT12 1.6%
SHRTFT22 1.6%
FLI 33.7%
BARO 102KPA
LAMBADA11 1.00
LAMBADA22 1.02
02S11 0.08mA
O2S12 0.08mA
VPWR 13.89-14.28V
TP_R 5.5%
AAT 19DEGC
TP_B 32.2%
PP_D 7.5%
CATEMP11 517deg C
APP_D 7.5%
APP_E 6.7%
TAC_PCT 22.4%
STS02FT1 1.6%
LGS02FT1 0.0%
STS02FT2 1.6%
LGS02FT2 0.0%

So last night I gapped the plugs and cleared the codes so a few values changed a little.
It was also fairly cold.

Other thoughts were how smooth is the engine supposed to be?
It really doesn't rock much,
But the resonant frequency at idle seems annoying.
Could the Transmission jerkyness be the Penrite Transmission fluid?
as personally,
I have never had much luck with that brand in my cars,
(Actually had some in a Getrag and dumped it in a week of use as it was worse than the old stuff (went to Redline Fluid))

It is still throwing up the misfire codes,
Although now number 6 is always first,
When it was number 3 before plugs were checked.
Have coils on the way, to hopefully get rid of that,
Although the timing being all over the shop seems strange.

Also could vaccuum leaks cause the misfires?
And is the PCV hose sucking flat a normal thing?

Cheers Everybody,
All help and replies appreciated

Post by **ggleavitt** » 25 Jul 2021, 12:59

There are others on this forum that have done more work on the V8 than I have and may have more input but I’ll take a poke at a first pass:

Idle should be smooth with no misses. Once you replace coils, you’ll omit them from the equation. If the valve covers have been off, then the coil grounds may have been compromised. The back bank (more common issue after VCG job) grounds support cylinders 2/4/6/8 so no help with your number 3 cylinder but I would still check all of them (2 front, 2 rear). I would probably do new OE plugs as well just for peace of mind if I were doing all the coils. Check all of your motor mounts as well, won’t be the source of your shakes but worn mounts will make it feel worse.

No PCV hose (does not matter which one) should be collapsed. Low vacuum in this system, like around minus .03bar (3 kPa or .43psi) per VIDA. The PCV in this powerplant serves more as a pressure regulator than a valve.

Can’t help with the transmission but I’ll suggest that you get the Penrite out and put in some Mobil 3309 or Toyota T-IV with or without an adaptation reset then see if anything gets better or not (at this point it seems like you have nothing to lose). Transmission takes around 7l, I usually get a case (12) if I’m pushing fluid through (I do pump out, not drain/fill) so I get more fluid cycling out.

ozxc90v8 · Post by **ozxc90v8** » 25 Jul 2021, 20:59

Thanks for that.
It has just has new genuine plugs,
fuel filter and PCV fitted a bit over a month ago.
It seems like their is more vacuum than what their should be,
which makes me think the PCV still isn't right.

It is pretty smooth really, even with the top engine mount off for access to plugs and coils.
There is no real audible miss in the exhaust.
It's just that it keeps triggering the misfire codes,
Then the engine light will come on.

Did notice the interior light, and lights on center dash for stereo seats and stuff, were flickering a bit at idle,
Like a low power situation, or perhaps a coil has shorted to ground.

Yeah I agree with the Transmission fluid. I think it's one of their multi-purpose ones.
Wonder if anyone else has had a similar experience with incorrect fluid?
Jerky movement on no throttle,
And horrible shudder onto TC lockup.
Penrite is not my pick for oils that's for sure, (was done by previous owner)
And Have found it often simply is no good for the task, even if it is stated on their bottles it is.

Post by **ggleavitt** » 26 Jul 2021, 10:00

"Did notice the interior light, and lights on center dash for stereo seats and stuff, were flickering a bit at idle,
Like a low power situation, or perhaps a coil has shorted to ground."

I forgot about battery and alternator. Either or both original?

ozxc90v8 · Post by **ozxc90v8** » 26 Jul 2021, 20:35

Actually it has a bit of a power steering leak so the alternator is likely oily,
Will have to check if it and the battery are genuine.
Is their anything on the alternator that would let me know?
I thought the voltage looked ok,
But it does move around a little.

What sort of battery should it have?
Will have to find it really haven't looked, yet.
Good points though.

Still don't know why the PCV hose is sucking flat,
Perhaps it's not the genuine hose,
But everything else seems to be.
It does pull crazy vacuum which does seem odd.
Wondered if perhaps the stock piece has a restrictor or something in it,
Have never seen such a large, approx 1 inch PCV hose before,
On any other vehicle.
It's the hose that goes to the manifold by the looks of it,
That is sucking flat.

Post by **ggleavitt** » 27 Jul 2021, 07:51

Photos would help folks help you identify that "flat" hose as well as the source of the leaks. PS pump probably needs replaced (FCP appears to be selling an o-ring kit to repair a leaking pump, have not seen feedback on that yet).

Battery is in the back of the vehicle under the flip up panel that's next to the tailgate. You'll need a 13mm to get the protective cover off then you can see if there's a date-code stamped on one of the posts, that's the giveaway for an original battery.

ozxc90v8 · Post by **ozxc90v8** » 27 Jul 2021, 21:48

It's the hose that goes from the PCV to manifold,
By the looks of it.
A bit hard to see there,
but can sort of see it's sucked flat in the pic.