2002 V70 2.4T misfiring ....Distributor Cap? ( coil on plugs) Topic is solved

[Messerschmitt101]

I have a 2002 V70 2.4T FWD.

Cylinders 4 and 5 are misfiring. Suggestion was a distributor cap.
I can't find that anywhere on RM European or FCP Euro.

Does this car even have a distributor cap? What else could cause this? Brand new spark plugs, coils and other ignition items were done a while ago.

Thanks all.

[- Pete -]

My first thought would be to try moving your ignition coils around to see if the misfire follows the moved coil. Be sure to carefully examine the wires under the top plastic covers & also be ultra careful when reinstalling the top plastic covers so not to pinch wires lying underneath.

You said the coils/plugs were changed, but were they replaced with Bosch/Volvo? If replaced with no-name/no part numbers on tops of coils I wouldn't be the least bit surprised if the coils have begun to fail. Edit: Even Bosch coils will fail eventually. It's not a "replace once & you're good to go forever" type deal.

No cap on these "newer" cars.

[erikv11]

What plugs were installed? Were they gapped?

[Georgeandkira]

How were cylinders #4 and #5 identified?

Did you use a code reader then erase the codes? It's always good to read codes, write them down then erase them.
In many cases it helps to see if and when they return. This is the argument for carrying your own code reader.

Your condition might be straightforward. Pete's suggestion of swapping the coils' positions is easiest, cheapest and smartest.
Leaving #3 alone, I'd relocate coils #1 and #2 into #4 and #5 holes and vice versa.

Do you do this level of work yourself? This job is easily doable if you're a beginner.

As above: Do you know if the correct plugs were installed? How long is "...a while ago"?

[Messerschmitt101]

Okay, thanks for the replies. I will try rearranging the coils.

The coils were done by a dealer mechanic at 134k miles, the car is now at 154k. I doubt coils will go bad after 20k, but stranger things have happened.
Spark plugs were also installed by a dealer mechanic before I bought the car.

Just thinking worst case: What are the odds of this being a blown head gasket? I've read that sometimes when two adjacent cylinders misfire it could point to the head gasket.

[abscate]

If you haven’t had an overheat incident, chance of a head gasket failure is almost nil.

Can you feel the misfire or are you just getting codes reported

[Messerschmitt101]

If you haven’t had an overheat incident, chance of a head gasket failure is almost nil.

Can you feel the misfire or are you just getting codes reported

It drove fine for.. like 15 miles yesterday.
After that, the engine began to shake violently (misfires) as it had done before spark plug replacement.
No overheats yet, but the coolant was empty, so I filled it up. The coolant tubes are new (about 30k miles ago), and I followed the bleed procedure. But again: No overheats.

[abscate]

Make sure all,the coils,are,bolted down firmly with the M6 bolt, that bolt is also,the ground connection

[- Pete -]

Hmm, (Abscates punctuation has me concerned) coolant reservoir empty (you then refilled), but you never made mention of receiving the "low coolant, stop safely" message.

You can get a compression tester pretty inexpensively at HF, not super accurate, but just to get an idea if any of your cylinders are scoring better or worse than others. This here might be a noble thing to do, I mean since you're gonna have the coils unscrewed, not that much more work to take a gander at the plugs. And while doing that, just measure compression on all 5 cylinders.

Low PSI on 4/5 could possibly indicate you are leaking psi into the cooling system, or elsewhere. This scenario (head gasket) is typically pretty unlikely though, as Abscate has said, but don't rule it out yet.

You also mentioned several times a "dealer mechanic" .... This was at a Volvo dealership? Or just an auto repair facility? If it was a Volvo dealership, I'd be pretty surprised if the tech used anything BUT Bosch coils & Volvo plugs (which was probably a $6-700 invoice).

[Georgeandkira]

Gotta disagree with you, Pete. If chasing down a problem includes doing a compression check ABSOLUTELY do all 5 cylinders especially on this engine as it is so easy. The other cylinders provide reference and deviation data.

You'll need a compression gauge with an extension. The one I have is flexible, cloth covered tubing. Because these hoses are often curved, guiding the hose to the spark plug hole such that it screws in squarely might be the hardest part of this project. A touch of dielectric grease on the O ring will afford a better seal. No need to muscle it in. Just be uniform with your twisting force.

COLD ENGINE
Cover off, you may want to mark the coils 1-2-3-4-5 for reference. A black Sharpie can be read from an angle or use a white paint pen to make dots or tally marks.
Unscrew and remove the 5 hold own bolts. Check to see if any coils pop upward-higher than the others.
Unplug and withdraw all 5 coils.
Carefully unscrew each sparky-poo. I use a back 'n forth motion and penetrant if they fight me. We don't want to damage any aluminum threads.
Now take your readings allowing the same number of strokes per cylinder. You'll see the needle react to each compression stroke.
Write the reading down as you do them.
Then you can UNIFORMLY squirt some oil into each cylinder in turn and take a wet reading. Don't pre oil all 5 as you want the oil to seal uniformly.
Write these readings down as you do them.

If you read only cyl. 4 and 5 and both were low you wouldn't be able to conclude anything. You need 'em all.

Someone here mashed one or more coils down upon the spark plugs crushing the rubber end a bit and failed to get solid contact resulting in a misfire. Use dielectric grease on the coils' boot end to prevent arcing.

As mentioned above, inspect the wiring harness to the coils for breaks in the wee wires insulation.

If you lived near Hackensack we'd be doing this today.