Misfire - 2005 XC90 V8

[Roger_850T]

Hi chitownV,

Thanks for the response. I haven't looked at the trims and O2 sensors, I'll try and do that.

I just changed the PCV valve - on the V8 that's about all there is, the valve and a few short hoses, and I also replaced the hoses.

It could also be the lower intake manifold gasket, as you mentioned. I haven't taken that apart yet with this issue. I last had that apart in 2019, maybe 60,000 miles ago. If I end up disassembling the upper intake manifold and injectors again, I'll

One thing I was thinking of - when I first dove into this, the spark plug on #1 was a little fouled. I moved the plug, and the misfire stayed, but I am now thinking that the cause of the fouling is the same root cause of the misfire. I'll post pictures shortly.

I will also say that at this point, the engine is "lumpy" when it first starts cold. I haven't yet confirmed, but it really feels like it's running on one less cylinder for a little while. I'm getting concerned that there is something wrong with the head gasket, or head, or valves, or something. I may dig out my borescope, although I don't have the little mirror that came with it any more, which would be useful for looking back at the valves. (I did look at the tops of the pistons, and didn't note any significant difference between #1, #3, and #5.)

Roger

[Roger_850T]

Here are the spark plugs for #1, #3, and #5 that I pulled out when I was first troubleshooting this issue. The fouled one on the left is #1.

20230722_170210665_iOS 1 (2).jpg (258.99 KiB) Viewed 786 times

Here is a close up of the plug.

20230722_170210665_iOS 1 (3).jpg (57.92 KiB) Viewed 786 times

Any thoughts on what this looks like? I can't decide if it's because it's running too rich, or if it's because there is oil getting into the cylinder. Or does it look like lean misfire?

Opinions please, I appreciate the input!

Roger

[chitownV]

The #1 spark plug could be all of the above as far as rich, lean, and oil. Do you have a picture of cylinder #7 spark plug because it looks like the plugs get gradually better the further away it is from cyl #1. The #3 spark plug's ceramic looks like it was running hotter than the other two. Is this a boot issue or has any oil dripped into the spark plug holes? The gradual difference, following the cylinder order, may be a sign of a vacuum leak at or near cyl #1 and the average A/F of bank 1 is taken with the O2 sensor for fuel trim adjustments.

An alternative scenario, but the same repair
It could also be the opposite where the issue is with, or closer to, #7 getting lean with a vacuum leak and then the fuel trims richen up bank 1. Cyl #1 is working fine, but gets too rich with the fuel trims, fouling the plug. If there's a vacuum leak making #7 lean, then that could also affect the cold start.

Were these pictures taken before the PCV? Did you clear the codes after you did the PCV and hoses?
When you took the upper manifold off, did you happen to take pictures inside the runners?

Also, check the timing if it's being pulled or if there's a healthy advance. The borescope could be small enough to get a closer look if there is a sign of a vacuum leak; it's worth a try for cylinder #1 or #7. Nothing to lose. You might even be able to run the borescope inside the upper manifold (and TB gasket & boot) to see if you can spot any light poking through from the outside, a sign of a leak. Just keep an open mind to where a potential leak could come from.

One last question, what oil are you using?
Have you read this post: https://www.swedespeed.com/threads/oil- ... st-8046070

[ggleavitt]

Couple points of visual reference for anyone not familiar with the motor: Dipstick on bottom is the front of the vehicle. Motor front to left:

B8444S Cylinder Number.jpg (18.39 KiB) Viewed 776 times

Oddly enough, cylinder 1 has the farthest vacuum path to the PCV. Dipstick to the left.

B8444S_PCVflow_Volvo.JPG (55.39 KiB) Viewed 776 times

These new plugs after resetting the injectors with new o-rings and attaching the clips ?

[bartoszXc90]

Hi,
fighting similair type of problem on cilinder 2. Bought car wit not running cil 2 and 5 with 400.000km. for me i did all new plugs, changed order or coils, replaced 2 coils and this helped for a while but problems of misfire at idle reoccur sinds that time is a ghost chasing. plugs are great color(even when was running 30%rich on idle on chineese injectors color was same, super clean so this sooth you see on yours must be oil).idle jumps 650-680 noticable.

i did compression check and head gasket leak test. compression is worst on cil 2 so here is my tip.. the weakest will be showing symptoms. no head leaks from coolant side at least. new pcv installed changed nothing, changed oil dipstick, oil cap seals as well. all rubber is trashed in this heat monster so i suggest to replace those. the other pcv hose replaced too(between te heads).

first big was pcv hose being split by too tight clamp on it. after new hose them was all good for some time. As split was widening more and more idle problems untill darth vader type pf sounds were coming pff the engone at idle amd squeek at higjer rpm-so was obvious to find the source of the leak.

2nd was leak in crank seal at aux belt sode! it was a big change afyer that. the same time i did clean injector and microfilter in it disintegrated so i replaced 4 injectors in that bank 2 with chineese ones. car was running great but about 3000km later too rich on that bank so i rebuilt and cleaned all original injectors, new microfilters, new seals (non volvo as volvo seal swelles an made a huge benzine leak under the car!!!they basically slide withoit resistance from the injector once wet in benzine WTF volvo). i replaced upper pleneum seals that time. lower seals were replaced too. new fuel presure regulator.

as one crank seal was a goner, i did the whole side valve cover seals too. top seals were.done before i bought car.i do expect tranny side seal to be not best, but not leaking yet. i can imagine some vacum leak there.

3rd was vacum hoses on the small vacum tank next to cil 2, they were put other way around, what hurted mileage and power. check those.

4th i did replace seals around variators acutators -on top of the engine u see them. oil was leaking there a bit and drowned the sparkplug of cil 2 from the top so missfire was obviously happening.

5th last time i did injector seals(afyer flood of fuel) i pit chineese ones, it made it really hard to put the injectors back in, bit it was evening already nd had to wrap stuff up before morning commute amd still kids to get to bed etc. so i just put it all back as fast as i could. i meeded.to retighten the pleneum and it helped some.

6th chineese.injectors were running rich so i got that error, afyer change to origibals i got trims back to 2-6% but now i get katalisator error on bank 2 and misfires. in can readouts all looks right, both banks behve same way following the loop. bit gets me to think that mybe lazy lambda sensor is at play as sometimes it stucks in both banks i am puzzled. so.lamda sensors are on my next todo.

7th dd wash engine with oil flush remedies 2 times already, lots of scorch in oil fiter during that clenup. also cams chain side cover was pretty dirty from inside from old oil burns.
8th clening mass flow meter

9th hypothesis on my engine i think engine is passing so much blowback gassess that it dillutes combustible mixture, since oxygen content is low in these burnt gasses is lowering oxygen content at lambda sensor thus ecu is leaning the mixture further causing missfire at some moments when it becomes too lean for that weak cilinder 2. rest of closed loop is withon margin for cil 2 to fire. thos explains why it was running fine on chineese rich injectors. this blowback should be verifiable i will check idle manifold pressure, i remeber from previois obseevtions it was 35 cold and 37 warm so pressure was rising but have not looked at it long time. i think this one is close to what somone mentikned about going from open to closed loop, then a misfire can happen. i speculate it will also show temporary changes in trims going back and forth as.ecu detects missfire.

btw error on missfire shows after like few hundrets of them or even thousands so dont think is a single event you have there.read the count before resetting.

maybe manifold pressure sensor is faulty/dirty? ecu calculates trims, massflow is smaller at leak in vacuum so leaner mixture. but manifold pressure should also be taken into account and mayne

[chitownV]

Sounds like a LOT of V8 issues. Wow . Good luck with it.

Hi,
fighting similair type of problem on cilinder 2. Bought car wit not running cil 2 and 5 with 400.000km. for me i did all new plugs, changed order or coils, replaced 2 coils and this helped for a while but problems of misfire at idle reoccur sinds that time is a ghost chasing. plugs are great color(even when was running 30%rich on idle on chineese injectors color was same, super clean so this sooth you see on yours must be oil).idle jumps 650-680 noticable.

i did compression check and head gasket leak test. compression is worst on cil 2 so here is my tip.. the weakest will be showing symptoms. no head leaks from coolant side at least. new pcv installed changed nothing, changed oil dipstick, oil cap seals as well. all rubber is trashed in this heat monster so i suggest to replace those. the other pcv hose replaced too(between te heads).

first big was pcv hose being split by too tight clamp on it. after new hose them was all good for some time. As split was widening more and more idle problems untill darth vader type pf sounds were coming pff the engone at idle amd squeek at higjer rpm-so was obvious to find the source of the leak.

2nd was leak in crank seal at aux belt sode! it was a big change afyer that. the same time i did clean injector and microfilter in it disintegrated so i replaced 4 injectors in that bank 2 with chineese ones. car was running great but about 3000km later too rich on that bank so i rebuilt and cleaned all original injectors, new microfilters, new seals (non volvo as volvo seal swelles an made a huge benzine leak under the car!!!they basically slide withoit resistance from the injector once wet in benzine WTF volvo). i replaced upper pleneum seals that time. lower seals were replaced too. new fuel presure regulator.

as one crank seal was a goner, i did the whole side valve cover seals too. top seals were.done before i bought car.i do expect tranny side seal to be not best, but not leaking yet. i can imagine some vacum leak there.

3rd was vacum hoses on the small vacum tank next to cil 2, they were put other way around, what hurted mileage and power. check those.

4th i did replace seals around variators acutators -on top of the engine u see them. oil was leaking there a bit and drowned the sparkplug of cil 2 from the top so missfire was obviously happening.

5th last time i did injector seals(afyer flood of fuel) i pit chineese ones, it made it really hard to put the injectors back in, bit it was evening already nd had to wrap stuff up before morning commute amd still kids to get to bed etc. so i just put it all back as fast as i could. i meeded.to retighten the pleneum and it helped some.

6th chineese.injectors were running rich so i got that error, afyer change to origibals i got trims back to 2-6% but now i get katalisator error on bank 2 and misfires. in can readouts all looks right, both banks behve same way following the loop. bit gets me to think that mybe lazy lambda sensor is at play as sometimes it stucks in both banks i am puzzled. so.lamda sensors are on my next todo.

7th dd wash engine with oil flush remedies 2 times already, lots of scorch in oil fiter during that clenup. also cams chain side cover was pretty dirty from inside from old oil burns.
8th clening mass flow meter

9th hypothesis on my engine i think engine is passing so much blowback gassess that it dillutes combustible mixture, since oxygen content is low in these burnt gasses is lowering oxygen content at lambda sensor thus ecu is leaning the mixture further causing missfire at some moments when it becomes too lean for that weak cilinder 2. rest of closed loop is withon margin for cil 2 to fire. thos explains why it was running fine on chineese rich injectors. this blowback should be verifiable i will check idle manifold pressure, i remeber from previois obseevtions it was 35 cold and 37 warm so pressure was rising but have not looked at it long time. i think this one is close to what somone mentikned about going from open to closed loop, then a misfire can happen. i speculate it will also show temporary changes in trims going back and forth as.ecu detects missfire.

btw error on missfire shows after like few hundrets of them or even thousands so dont think is a single event you have there.read the count before resetting.

maybe manifold pressure sensor is faulty/dirty? ecu calculates trims, massflow is smaller at leak in vacuum so leaner mixture. but manifold pressure should also be taken into account and mayne

[drosser]

Any update on this? Was it a leak in the lower intake manifold? I am getting the same symptoms on mine. I also did a leak down test and all checked out good. Makes me think that what you hypothesized is correct- that there is a leak in the intake on cylinder 1 in the lower manifold.

Also- VIDA only reports misfires (the counter only counts) at idle. Bring it up to 1000rpms and the misfires stop counting. Foot off the gas and they count up at 1 per second or so- the rate of misfires will vary, but that is the average rate.