Yet another misfire thread - Cylinder 3 - No compression

[TisMe]

Compression test
#1- 165
#2- 165
#3... 0
#4- 170
#5 -170

Scary codes
ECM-3503
ECM-3533

Used to be a P0303 but that's changed/escalated?

Replaced the following in relation to my very miserable idle and chug-chug performance:

Spark plugs
All coil packs (overkill I know)
Cleaned throttle body
New filter baskets and o-rings for fuel injectors (hoped this would improve MPG)
Both 02 sensors
TCV just for "fun" (provided noticeable increase in boost power)

Also run a fair bit of fuel injector cleaner every other fill-up. I'm convinced the cleaner did help over time. I've done other things as well, but I'll keep the listed maintenance relevant.

It felt as if every component I gradually replaced improved my performance, until I finally did enough where my idle is quite nice. There's still a noticeable but low-key miss, combined with a dive bar quality light show party in my dashboard, but this maintenance made her "drivable" again.

No more hunting idle. Sometimes I'll stall at a stop sign- very rare. Last month after sitting for 4-5 days along a sun-soaked dusty road, the hour-long trip home had some pretty chuggy low-end with awkward electrical symptoms like my oil lamp flickering at a stoplight despite my perfect oil level. This has not happened again since that day.

What makes the misfire rear its dirty head is when I'm cruising between almost exactly 50-60MPH, then lightly hit the gas to make mild speed adjustments. My engine starts chugging again and I can hear a metallic tap-tap-tap coming from the engine. If I activate geartronic mode and downshift to 4th, it mostly subsides. If I activate lead foot mode and kick in the boost, this also makes it subside. And finally, when I'm over 60-62MPH, this symptom does not happen. Secondarily finally, if I'm hitting the on-ramp and power through all the way to 70-80MPH, it's as if the misfire doesn't exist.

At this point, I've likely answered my own question and need to pull the head. What I've surmised is that cylinder 3 has a burnt valve(s) with a leaky valve stem(s). But I'll be frank; this is my first time diagnosing internal engine damage and therefor I've come to pick the brains of more knowledgable folks

So to create a question; before I open my early Christmas gift and pull the head, I was wondering if anyone may have solved a single-cylinder compression issue through some random part they've thrown at their car that I have yet to replace. I know that's a long-shot considering the 0 compression, but cars have strange gremlins sometimes.

Did I mention that the night my misfire showed up, the engine felt as if there was a small explosion internally? I thought she was done for, but I got her home and replaced what I did and things are nearly dandy. Perhaps that was a piece of a valve somehow breaking off? Makes me unsure of whether there could be worse damage inside than what I anticipate, perhaps insinuating more than a head rebuild.

But to put her performance in other words, it's pretty dang good and an awfully smooth aside from 50-60MPH acceleration.

And I do know I should have sidelined the car the moment this happened, but duty calls and I had to do what I could to stay on the road. I put on very little mileage before I managed to temper down the misfire.

I believe that's all the relevant tidbits. Any input and random insights, as always, is very much appreciated!

[abscate]

Yeah, you swallowed a valve. Pull the harness off number 3 injector and you can still drive it for 3141.59 miles without problems , if you stay off the gas and drive at 45 mph

Save up the kroner for a head job, about $400-500 all in

[TisMe]

Yeah, you swallowed a valve. Pull the harness off number 3 injector and you can still drive it for 3141.59 miles without problems , if you stay off the gas and drive at 45 mph

Save up the kroner for a head job, about $400-500 all in

Thanks for the intel! I should be able to fully sideline her for the head job within 2-3 weeks.

So, I've been driving with my coil pack harness disconnected... this perhaps means my injector is still spraying fluid, huh?

I did it like this because when I removed the injector harness, the OBD reader gave me a very weird code insinuating I lost power to cylinder 2 as well. Couple this with my absolute abysmal power, it was a chore to even get to 45mph. It made me think, perhaps incorrectly, the coil pack was the proper disconnection.

[erikv11]

I think the head job is closer to $800 by the time you wrap it up, depending on what else needs done e.g. timing parts. Abscate has done a couple recently, not sure how he gets away for less $.

That's odd about the loss of power, on this car there should be no change when unplugging the #3 injector. A code change maybe, but not a running change. But dumping unburnt fuel into the oil is going to become a problem, you'll want to figure out how to disconnect the #3 injector. Coil wire you can then leave plugged. Have you tried it that way, injector unplugged but coils all connected?

[firstv70volvo]

...

So, I've been driving with my coil pack harness disconnected... this perhaps means my injector is still spraying fluid, huh?

I did it like this because when I removed the injector harness, the OBD reader gave me a very weird code insinuating I lost power to cylinder 2 as well. Couple this with my absolute abysmal power, it was a chore to even get to 45mph. It made me think, perhaps incorrectly, the coil pack was the proper disconnection.

Dumping raw fuel into the catalytic converter is not good for the life (overheats) of an expensive catalytic converter in addition to washing away oil on the cylinder wall in addition to oil dilution from too much gas. Some engine management systems shut of the fuel injector to badly misfiring cylinders, not sure if Volvo's ECM does this or not. If you could avoid driving the car until the cylinder head is done and compression restored it might be prevent other expensive problems from occurring. Sometimes one problem creates an expensive snowball effect of other problems.

[chrism]

If there was a noticeable loss of power when you disabled the #3 coil and/or injector that would indicate #3 was still producing SOME sort of power. Maybe it should be left active until repairs are performed.

[erikv11]

At 100 PSI maybe, but at 0 PSI #3 isn't doing anything. Especially given that the #3 coil was unplugged. It's hard ((for me!) to explain the behavior when unplugging #3 injector, but there's no residual power hiding in #3.

People have driven P80 cars for months with a burnt valve and one injector unplugged, with no apparent (or expected) ill effects. Haven't really seen it done on P2 cars I guess.

[TisMe]

That's odd about the loss of power, on this car there should be no change when unplugging the #3 injector. A code change maybe, but not a running change. But dumping unburnt fuel into the oil is going to become a problem, you'll want to figure out how to disconnect the #3 injector. Coil wire you can then leave plugged. Have you tried it that way, injector unplugged but coils all connected?

Correct, I took it for a 30 minute drive a while back with injector 3 disconnected. I pulled over halfway through because the power was so bad. Ran the OBD, got a code insinuating that cylinder 2 was also losing its fuel power. Made me think that this could be worse for the system, and proceeded to reconnect injector > disconnect coil. Got back on the road, lots of power was restored. Something about the way the injector harness is wired seemingly causes a miscommunication with the plug behind the one that is removed.

I'll replicate this before day's end so I can pull the code, for curiosity's sake.

At 100 PSI maybe, but at 0 PSI #3 isn't doing anything. Especially given that the #3 coil was unplugged. It's hard ((for me!) to explain the behavior when unplugging #3 injector, but there's no residual power hiding in #3.

My exact assumption, that's why I trusted the code and figured I may be causing more havoc by #2 injector no longer handshaking with the #3 injector plug removed. With ONLY #3 coil removed, the power seemed to be on par with having everything connected. But now that I think on it more, that probably does not remove power from the injector because it's farther up on the wiring squid.

Dumping raw fuel into the catalytic converter is not good for the life (overheats) of an expensive catalytic converter in addition to washing away oil on the cylinder wall in addition to oil dilution from too much gas...

Appreciate the systematic synopsis! This is likely why the codes read how they do; "Misfire - TWC Damage". I don't think it's saying there is currently damage, but that damage can occur. I say this because I had my midpipe off last month due to my Walker muffler rusting out on 495 during rush hour (not sure on the muffler's age, I generally like Walker/Starla). Took this as an opportunity to examine my cat, expecting a clogged up mess, yet the precious screen looked immaculate.

I'd like to keep it that way. But is it possible there's already damage despite the screen being great? Hmm...

If there was a noticeable loss of power when you disabled the #3 coil and/or injector that would indicate #3 was still producing SOME sort of power. Maybe it should be left active until repairs are performed.

I was thinking this too, until I did the pressure test. Didn't expect to get a 0 definitely some raw fuel hitting the system if this unplugged coil isn't killing the injector signal.

[erikv11]

Yes, those cat codes are just warnings of what could ensue, not an indication of damage.

[firstv70volvo]

Have you removed and looked at the number 3 spark plug after running with the coil disconnect, fuel injector connected for cylinder 3? If it's dry I'm it may indicate the ECM is shutting down the fuel injector for that cylinder. Not sure what's going on when you disconnect the fuel injector for cylinder 3 and lose power and get a code for cylinder 2. What's the actual code you get for cylinder 2? In a case like this, which doesn't make sense, I would point an infrared thermometer at the each of the cylinder exhausts outlets to see which cylinders still seem to be firing and contributing power and which are dead.