P0305 Code (misfire code) Topic is solved

[erikv11]

Also, consider sleddriver's comment here about the coil wire, it's a real stretch for what you are seeing but it doesn't hurt to just check it https://www.matthewsvolvosite.com/forums ... 61#p401661

[songzunhuang]

This weekend I took the next step. I performed a compression test on the car. Here's what I saw.

#1 = 170
#2 = 162
#3 = 160
#4 = 156
#5 = 150

Results for my compression test for the highest and 2 lowest readings.

Compression st.png (956.01 KiB) Viewed 2522 times

So there is definitely a variance in the the compression with #1 being the highest, but is it enough to cause a misfire? What do you think? With #4 also a bit lower, why doesn't it ever throw a code? I expected to see more variance in #5.

I ran a bottle of Seafoam in the car to loosen up any gunk that may have collected around the valves and intake.
Also, I swapped the #5 and #1 fuel injectors for good measure.

I drove the car aggressively for about 20 minutes. And as usual, it was fine on the freeway and around town as long as the rpms was above idle. At idle, it was still a bit lumpy and then...it happened.

I got a P0171 and a P0305 code.
P0171 is a lean condition - I figured it may have to do with the Seafoam treatment and all my blasting around town.
P0305 is the misfire on the the #5 cylinder again. The injector swap didn't make a difference.

I am very close to my wits end. Looking for suggestions before I drag to the repair shop and get possible terrible news.

Oh, a hint for folks on the forum. I borrowed the compression tester from O'Rielys Auto Part. They have a program where you "buy" the unit and have 48 hours to return it for a full refund. It's a nice service. Basically the deposit was $43 and then I got it back when I was done.

[abscate]

Song...check you intake manifold bolts around cylinder 5 for correct torque.

This is a tough one!

[erikv11]

... This is a tough one!

That's what I was thinking.

Song...check you intake manifold bolts around cylinder 5 for correct torque. ...

Hadn't thought of that though. I keep wanting to say "well if the stumble is at idle, top suspect is vacuum leak " But I know Song has checked, plus why only #5? IM might make sense for just #5.

[songzunhuang]

Song...check you intake manifold bolts around cylinder 5 for correct torque.

This is a tough one!

Well, I checked the bolts on the intake manifold. Sorry to report that it wasn't even a little bit loose.
When I changed the PCV system several months back, I had to remove the manifold and replace the gasket. So I was pretty sure it wasn't going to be a leak there, but since I am running out of ideas, I'll try anything.

I'll keep hanging on for more suggestions. However, I fear a call to the Volvo dealer is in my future.
And thanks in advance for any other ideas.

[abscate]

This might not be great help but step back from the dogma that cylinder 5 is Giving you trouble. There is no sensor on each cylinder,the ECU detects a misfire (knock sensor?) and then uses the cam and/or crank sensor to figure out which cylinder it is. If you gave mixed signals or one of the sensors is wonky, the wrong cylinder will code.

Msybe work you way down the line swapping two plugs and then injectors to try and get that code to migrate.

[rspi]

Wow! This is another marathon misfire thread. These are usually tracked down pretty quick.

Your compression numbers are probably falling due to cranking battery drain.

1. Check compression.
2. Check timing.
3. Double and triple check for intake manifold leak.
4. Get OEM ignition parts.
5. Check for cam seal leaks.
6. Verify spark plug order.
7. Hire a professional.

[songzunhuang]

Wow! This is another marathon misfire thread. These are usually tracked down pretty quick.

Your compression numbers are probably falling due to cranking battery drain.

1. Check compression.
2. Check timing.
3. Double and triple check for intake manifold leak.
4. Get OEM ignition parts.
5. Check for cam seal leaks.
6. Verify spark plug order.
7. Hire a professional.

Alas, I think I am down to #7.

I'm going to arrange time to take the car to the stealership.
It wouldn't bother me much if I was just get a misfire but the car ran fine. The issue is that at idle, it's really rough and lumpy. So much so that it's hard to ignore. Sometimes I think it might stumble and die (I am referring to the engine).

[erikv11]

Starting fluid is supposed to be really good for finding/testing for intake manifold leaks. I haven't used it but have read about it many times. It is really acting like a vacuum leak (except for only giving codes for #5).

[rspi]

I just looked at a car today with the #5 random misfire code. The crank wire was to close to #5 cylinder spark plug wire. Moved the wire and the misfire stopped.