recently bought a 2001 Volvo S40 1.9T. Starts fine and idles fine except for the occasional stumble. Revs up no problem. Under load however it has no power and keeps missing. Hooking up a codereader I constantly get code P0302 - miss on cyl#2. It previously also threw P0107 but replacing the MAP and boost sensor cleared that up. No difference in how it runs though. No difference after replacing the fuel pressure regulator either. Connected one of those lights inline with the sparkplug and it does miss on cyl #2. I already cleaned out the idle motor with brake cleaner, cleaned and regapped the plugs (OEM) to 0.75mm which look fairly new, swapped the #3 and #4 coils around and same for the wires. Just for good measure also then replaced the #3 coil and wire (as it goes to #2 as well). No difference whatsoever. I also noticed that I may have a new MAF. Hooked up this plumbing rig I made to my air compressor to listen for air leaks. Seems to hold some pressure, there is a very slow leak but don't think it's the issue. Sometimes a little quicker and sometimes barely accelerates. Any ideas?
2001 Volvo S40 1.9T
cleaned and gapped plugs
swapped coils and wires
replaced MAP and boost sensor
replaced fuel pressure regulator
pressure tested system (very slow leak possibly at the IC inlet but not likely a boost leak issue)
cleared error codes but P0302 is always there
hooked up light inline with spark plug to verify that missing
MAF seems to have been replaced
cleaned idle motor
ran SeaFoam through oil, intake, and gas
Hi Customer. Thank you for asking your question on JustAnswer.
What is the engine compression on that cylinder?
What is engine vacuum at idle?
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Thanks for your prompt response. It settles to 20Hg at idle (though haven't had a chance to see if there's any boost yet) and up to 25-30Hg lifting off throttle.
My compression tester doesn't go deep enough for the spark plug opening so will see if I can get another one to test it tomorrow.
Also, if kept below 2-2.5k rpm at light throttle, it at times hardly misses, while at others (often after a hwy run) stumbles so badly that it barely accelerates.
Will get back to you re the compression to see if it's a valve issue.
We had one that had a bad crank position sensor. It was giving a bad signal to ecm and kept getting a misfire on #5. Not sure if that is your case but we need to keep it in mind.
Did you try a new plug by chance, does not happen too often but will lead you in wrong direction. Does not sound like a weak cylinder it would be a dead miss at idle. This acts like the old cars when the points would bounce... New cars have crank and cam sensors.
Hmm... maybe for the crank sensor. I did swap the plugs around when I cleaned them and it made no difference, the miss stayed on cyl#2. They look to be fairly new as well. When the map was bad, after a while the ECU would report a miss on all cyl's but now it's only and always P0302. Another thought I have is the temperature sensor but there isn't really a consistent difference in how it runs between hot and cold. Will do a compression test on all cyl's anyways just to rule that out. I know Audi's but with this Volvo need to lookup every sensor to find out where it is. There is also a check valve with a connector coming off it just at the intake to the turbo, disconnecting it seems to make no difference at all nor brings up any new codes. Not sure what it's for though.
Here is some ammo for you
Fantastic! Thanks! BTW not that it's really relevant but it seems to boost to about 7psi which I believe is normal for the low pressure set-up on the car.
Also, correct me if I'm wrong but doesn't it need to reference the the crank sensor to start? Do you happen to know if the crank sensor might be on the transmission bell housing? Is there a resistance check that can be done accross it? Will go hunting for it on the car tomorrow.
Inductive sensor with a permanent magnet Resistance 125.5 ±17 Ohms
2 wire sensor. Produces an ac voltage signal.
I ended up fixing the problem completely by switching to new copper core plugs. Weird! But works great now! Thanks much for your help! Merry Christmas!
Glad you got it fixed. thanks Jim B
40 years Import and domestic AAA Approved Shop owner 30 yrs
FYI the problem came back after a few thousand kms and switching to new plugs would fix the problem for a bit but it would always come back. I ended up swapping a couple of the coils and it ended up fixing it. Thanks much! ...now for the EVAP CEL that just turned on...
coils do fail at times. thanks for getting back to mejimJim B41121.6441999653