Replaced all new 5 ignition coils, but still get PO300, 302, and 304...

[orvieto]

Thank you for your help as always.
I replaced 3 failed ignition coils (Bosch) with new Volvo spark plugs a few years ago. And I bought 2 more coils just in case and kept in the car.

A few days ago when we were on the highway, check engine light started flashing and felt misfiring.
I parked the car and replaced two coils (those were original with Volvo logos and easy to identified).

It got much better and we made a home safe, but still felt misfiring.

Today I replaced 5 all new coils (Bosch), and it got better. However I still feel misfiring, and get PO300, 302, and 304 codes.

Any ideas what is wrong?

[orvieto]

Is it possible that because I drove 2 hours + with failed coil (s) a few days ago, so spark plugs are shot or completely wet or fouled?
I was lazy and didn't bather to check them when I replaced coils.

[orvieto]

Installed all new spark plugs. So all new coils and new spark plugs, but still feel slight misfiring with engine checking light flashing especially when the engine is under stress or stop and go driving. Also I still get the same codes: PO300, 302, and 304Â…

Anybody has any ideas?
Thank you.

[hoo8it]

IMO the only other thing left to check are injectors or wiring harness to coils
this is one of those things that really benefit from having a diagnose via VIDA DICE or dealership/indy shop it will narrow your problem down as they can read the volvo specific DTC codes that are set off. of course you can do this with your own VIDA/DICE if you have one or know someone with one.
It'll save you money in the long run so you dont have to throw parts

[Xfingers]

Yeah, you might want to check your electrical harnesses leading to your coils for broken/exposed wires.
Some people on Swedespeed have reported good results replacing their worn harness with a certain replacement made in Russia (?) available on ebay (?) that wasn't too expensive. You ought to be able to find it with a search if you want to go that route.

[hoonk]

PO300, 302, and 304 codes.

Any ideas what is wrong?

You need compression, spark at the correct time and the correct amount of fuel at the right time.

What's the compression? What's the fuel pressure and volume? (Let's accept the ignition system is ok )

[albertj]

Does anyone think there may be a problem with the VVT? orvieto, did you re-set the codes after replacing the coils?

[orvieto]

Thank you hoo8it, Xfingers, hoonk, albertj,

Sorry I didn't get a notification from the site and thought there was no answer. Really appreciate your inputs.

Last thing I did was swapping the cylinder 2 (bad code) with 1, and 4 (bad code) with 3, but code didn't follow. So I gave up and made an appointment with my dealer (they just replaced recall air bag part). They know that I'm not dealer customer, but are very nice, so I have no choice (they said flashing engine check light is troublesome and something internal, injector or gunky valve seat, most likely you don't want to hear the cost to fix).

Meanwhile I have the following questions:
1) RE: wiring harness - you are talking about this? How can I connect it to main cable?

https://tinyurl.com/2crd94bv

2) RE: VVT - don't know what re-set mean? Please explain. I erase the code, but my cheap scanner doesn't have anything else.

Thank you very much again for your inputs!!
Orvieto

[Xfingers]

Meanwhile I have the following questions:
1) RE: wiring harness - you are talking about this? How can I connect it to main cable?

https://tinyurl.com/2crd94bv

Orvieto

This thread from swedespeed has the info on the harness which is different from the link you posted:
https://www.swedespeed.com/threads/2.../#post-7498967

Unfortunately, the ebay link to purchase the harness doesn't work! I didn't have a need to order a harness myself so I only know what's posted in the thread. You could try adding your own post to the thread to see if any of the other posters have more info on availability. Maybe closely inspect the wiring on your current harness and make an assessment of its condition. It might or might not be causing your issue.

EDIT: I found some more info on the wiring harness, though some think $175 is a little pricey:
https://www.swedespeed.com/threads/t...arness.647649/
https://www.prancingmoose.com/volvoh...cylcoilharness

Orvieto, I'm not necessarily saying a new wiring harness is the solution to your problem. I'd want to see cracks, breaks or deterioration in the current harness first.

[orvieto]

Thank you Xfingers,
Yes I understood. I looked where I can, but everything looked OK. I will bring the dealer this week, so I will let you know what they will find.

Thanks again!

This thread from swedespeed has the info on the harness which is different from the link you posted:
https://www.swedespeed.com/threads/2.../#post-7498967

Unfortunately, the ebay link to purchase the harness doesn't work! I didn't have a need to order a harness myself so I only know what's posted in the thread. You could try adding your own post to the thread to see if any of the other posters have more info on availability. Maybe closely inspect the wiring on your current harness and make an assessment of its condition. It might or might not be causing your issue.

EDIT: I found some more info on the wiring harness, though some think $175 is a little pricey:
https://www.swedespeed.com/threads/t...arness.647649/
https://www.prancingmoose.com/volvoh...cylcoilharness

Orvieto, I'm not necessarily saying a new wiring harness is the solution to your problem. I'd want to see cracks, breaks or deterioration in the current harness first.