02 V40 Misfiring problem during acceleration

sstoynov · Post by **sstoynov** » 20 Jul 2014, 11:04

Hi,

My '02 V40 has misfiring problems, I replaced a bunch of parts and it still persist.

I replaced the spark plugs, put 2 new aftermarket coils, and I still have the misfiring. It throws a code that various cylinders misfire.

The interesting part is that at idle there is no misfiring. If I take it easy on the gas pedal it is fine. Only during medium to hard acceleration it starts to misfire and the check engine light comes on.

Could it be the fuel pump or any other non-electrical related issue?

Post by **regent** » 20 Jul 2014, 13:26

sstoynov wrote:.
...I replaced a bunch of parts...

You are running lean at a load, the old plugs may have already 'told you so'. This could be caused by anything from insufficient fuel pressure to incorrect air metering. Besides plugs and coils, did you change the fuel filter?

sstoynov · Post by **sstoynov** » 20 Jul 2014, 13:31

no fuel filter change. I am having issues as well with the fuel pressure regulator - it takes forever to start - planning to replace it soon (replaced it before but obviously need another one).

Maybe the rich mixture you are suggesting explaining some backfire during hard acceleration.

Post by **regent** » 20 Jul 2014, 13:56

I was actually thinking lean if fuel pressure is geting low. Can you look at your fuel trims; if you don't have VIDA, you could do that with something generic (like TORQUE) that will pull STFT and LTFT, as well as many other variables and then go from there.
And you want to change that fuel filter; if it is clogged, the pressure at load may not be enough.

sstoynov · Post by **sstoynov** » 21 Jul 2014, 16:07

Actually, I just checked the codes and here they are: P0301, P0302, P0303, P0304 - in other words - misfire from every cylinder. Once I cleared the codes - I kinda feel it became a bit better, but still there was misfire.
Also I remembered that I replaced the fuel filter 30k miles ago.

I believe it is more an electrical problem then fuel. Havent replaced the hi-voltage cables yet, but borrowed from another V40 and that didn;t fix it.
Out of curiosity - In your experience do you rely on aftermarket coils?
And are there specific spark plugs recommended for Volvo I should use? I heard that Volvos are very picky on plugs

Post by **regent** » 22 Jul 2014, 08:53

sstoynov wrote:... I heard that Volvos are very picky on plugs

Yes, you heard right; I would stick with the OEM plugs and BOSCH wires (or coil packs, whichever you have) BOSCH are the OEM for the ignition components.

In my opinion, that 'all cylinder misfire' will still require a look at the fuel trims to pinpoint the actual culprit. Clearing the codes by itself is not a permanent solution.

When you get another misfire code, you may want to read the freeze frames as well before clearing it.

sstoynov · Post by **sstoynov** » 22 Jul 2014, 12:40

Regent, thanks for the tips. I ordered Bluetooth OBD2 adaptor and will get Torque to measure the fuel trims.
Since I am new to Torque - at what RPMs should I get the freeze frames ? idle?

Thanks

Post by **regent** » 22 Jul 2014, 13:43

The OBD adapters like ELM 327 usually come with a CD ROM that has the expanded version of Torque(better than the free apks from Google Play).

Freeze frames are like snapshots taken every time a code is set, and you can read them when you pull the code. You can see the specifics like RPM, coolant temp., engine load %, etc., which are the 'frozen values' at the moment the code was triggered, and therefore, the RPM may be any given number.

Since you seem to be idling OK and your issue only occurs at acceleration (load), I say drive until you get a code again, and then go from there.

Cheers!

sstoynov · Post by **sstoynov** » 27 Jul 2014, 12:33

I got the full version of Torque for Android and I was able to capture some fuel trimming results.
The SFTF1, during hard acceleration and a lot of misfiring goes up to 26%. And also during normal acceleration - down to -10%. The Check Engine light blinks and after that disappears. I have now P0301 and P0303 showing as pending and I guess since the check light disappears I am not able to do freeze frames.
I will drive around until I have the Check Engine light on permanently and then I will try to get the freeze frames.
Uploading some screenshots.

Post by **regent** » 28 Jul 2014, 06:25

sstoynov wrote:...
The SFTF1, during hard acceleration and a lot of misfiring goes up to 26%. And also during normal acceleration - down to -10%...

Your findings indicate that during accel. you are running lean (for whatever the reason behind that is), and the computer is attempting to increase the duty cycle of the injectors to compensate with the 26% Short-Term Fuel Trim, which proves that the problem is fuel-related. (During accel. the vacuum goes down considerably, and that's why unmetered air like a vaccum leak will be out of the equation for right now).

If the misfire codes keep setting on one or two particular cylinder(s) only, it could be clogged injectors, and I would clean them all. However, if you see random misfire codes (like you previously mentioned, I think) then it is general fuel starvation (pressure regulator or a restricted flow for some reason such as filter, pump or even a pinched/kinked fuel line).

I also recall your filter was 30kmiles old, but consider this: if you had some contaminated fuel, the filter may have taken a shot already. Also, if you used an aftermarket replacement, verify that it is adequately sized; if too small it will likely get cloged prematurely.
Yours looks like the one on my S60:
http://www.fcpeuro.com/products/volvo-f ... 90-wk822-2