I started off with cylinder misfire 3. I've changed spark plugs, ignition coils, fuel injectors, and checked compression. All checked out and yet still misfire Cyl 3.

When I changed the fuel injectors, I gained cylinder 2 misfire. The only time it doesn't misfire is when I give it revs in P or N.

If I drive it or let it idle it's misfiring consistently. I also have a P0455 evap code which I don't know if it's related.

All I can think is FPR or IACV. IACV has been cleaned somewhat recently, but could still be broke?

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typically evap leaks are not noticed while driving but can be the source of a vacuum leak which can upset fuel trim. Do you hear/feel the misfire or are you going by the OBD2 scanner/fault code reports? Given the P0455 is a "large" evap leak, it could also be messing with your fuel pressure. On the 1.9T the common symptom for a failed FPR is long cold start cranking. Quick test is to pull the S shaped vacuum line off the bottom and see if any fuel drips out (due to torn diaphram).

 

I can definitely feel it. It feels like a lean misfire IMHO but you can see, hear and feel it. She starts up everytime without issue, BUT misfires at idle or under load. Only when I give it revs under NO load does it fire properly.

 

Also, on the 1.9Ts the wiring harness to the coils often can get cracks in the connectors/insulation which can cause misfires. I wound up just replacing mine when I did the coils and plugs - google Volvo 30662305

 

I had my mechanic repair the wiring to the coils and the misfire seemed to get worse after that. Wondering if since I'm changing everything, but the FPR, if it's getting weaker and not able to supply as much fuel.

 

FPRs have a diaphram that can tear and allow gas to bleed off into the vacuum line which can cause misfires and poor cold starts. Its a 15 minute fix but the part is like $100-150!

 

I'll check today. Thank you so much. I've done so much to get the misfire rid of, hopefully this it it! Cheers man!!

 

I recently had a P0455 large leak code on my 04 S40. Turned out to be the purge valve located on top of the rad (right side). Check a couple of things - disconnect the elec connector and 2 hoses and apply 12 volts to the solenoid to be sure is clicking. Also blow in one hose fitting, should not pass air as is energized to open. My would pass air even though solenoid was working, thus big leak. Note to remove the valve from rad, push plastic tab at front in rectangular hole and lift up the valve.

Also, I found when I had a bad FPR, I installed a second hose on the manifold and plug the opening, I also plugged the opening to the hose leading to the FPR (used a couple of small phillips scredriver fittings). This eliminated the leak and the FPR functioned fine/eliminated hard starts. I ran this way without any issues fro a month until I finally bought a FPR on Amazon for $100.

Good Luck

 

I'll look into that purge valve. I've had it since I've owned the car and there can only be so much wrong at this point haha.

I went ahead and ordered an FPR. I'm gonna get one off a junkyard volvo and see if that'll will work. Might not work too, but worth 8 bucks just to see. Thank you for the help! I'd like to have no CEL for a bit, hopefully all this fixes it

 

So get this, I installed the new FPR and it got a bit better, but will not get into boost and will misfire and even sometimes backfire under load/boost. Any ideas?

 

You mentioned that coils and plugs were changed, what about the wires that lead from the coils to the non-coiled plugs? If I recall, coil 4 runs 1 and 4 and coil 3 runs 2 and 3. Given you have issues with 2 and 3 and the coil is ok and fuel supply is ok, I suspect the cable to 2 is bad and/or the harness connector to coil 3 has an issue. It is a common problem with these connectors as they are subject to lots of heat. Open the connector and remove the 2 contacts, inspect the wires/crimps and connect direct to the coil, see if anything changes.

 

I'll be checking this out tomorrow. I really appreciate it. Hope that's it. I really really do

 

Look at the coil pack on cylinder 3. I think I found my misfire problem. The left contact is OK, but the right one can come off with no effort, literally.

 

I referenced the replacement part number for the harness earlier in the thread. Tasca parts has the best prices I've found for dealer parts - they are out of RI so you may find a local store faster to ship.

 

I talked to my mechanic and the guy who usually works on my car wasn't there so he'll be doing the job this time and I believe they are able to get the harness connector faster than I can.

Im hoping that this will finally fix that dang misfire. Thanks for the help!

 

Sounds like the connector was the culprit. If you are going to replace it for sure, why not give it a little squeeze with pliers to tighten it up on the coil contact and see if the misfire stops? Here is the connector you are looking for if you don't want to go with a full harness. Will need a couple of butt splices to crimp the wires end to existing harness. Let us know the outcome.

Don't forget to check the purge valve operation I mentioned earlier in this thread.

https://www.ebay.com/itm/223769705759

 

I agree - no need to replace an entire harness just for a loose connector and a buggered wire. Splice properly (I like to solder and then cover with heat-shrink on critical applications like this), and snug down that connector so it's tight again. Much less likely to induce "new and interesting problems" that way!

 

I just noticed the shipping $ on the ebay link. This is more reasonable for a set of 2. Go 3/4 down the web page for the S40 kit.

https://www.240turbo.com/volvoharnes...ml#4cylplugkit

I also read the connector is the same as the side blinkers on the front fenders. If you have access to a junker, check it out, cut them off with a 6 inch lead and reuse for the coils. Worth checking out.

 

That's not a half bad an idea.

I'm gonna take it back to the mechanic just because they're gonna fix it and fix it right. I'll let all you guys know what's happening as things get fixed.

 

I'll make sure to keep that in mind, but the shop is going to fix it at no charge to me. I do need to learn wiring though. The more I go on the more helpful it seems to be