Shutting down cylinders?
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    1. #1
      Global Moderator tmtalpey's Avatar
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      Shutting down cylinders?

      My 2005 V50 T5 did a surprising thing yesterday - anyone else experienced the following?

      At a stoplight, I mistakenly started off with the car in third. It coughed a bit and I pressed the gas harder before I realized the problem. The car then shuddered and the CEL blinked, indicating a misfire situation.

      Ok, oops, I thought, and double-clutched into first and hit the gas. The car moved forward ok, but with a distinct regular hiccup, and a continued flashing CEL. Pulled over and went to neutral, the situation continued with a now-steady CEL. It seemed to me the car basically shut down a cylinder (or two).

      At that point I figured stopping the engine and restarting would clear it, and it did. Car is fine, no CEL. But... why didn't it recover on its own? In 14 years of driving it, I don't recall this ever happening, and I've had several flashing CEL / miss situations.
      Last edited by tmtalpey; 01-13-2019 at 08:42 PM.
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva Forge CBV, Elevate rear swaybar and torque mount, Snabb shift kit, etc.
      2016 XC60 T6 AWD
      1956 PV444 complete, running
      1956 PV444 very original, very rough

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    3. #2
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      I've also started out with my s40 in the wrong gear. Once I realize it, I just switch gears to 1st or 2nd. It's amazing how close the m66 gear ratios are, so even in 3rd or 4th, the car will start to move from a stop.
      I'm not sure why you got a flashing cel, but any time you get a flashing cel, the car is telling you it's a very bad problem so u need to fix it right away. A solid cel is not as urgent so it's odd that it went from flashing to solid.
      Have you scanned the car to see what the codes are. I'd think a flashing cel would definitely have stored codes. Plus u mention having flashing cels previously. So even though this happened when you recently bogged the car, it's happened before so codes are the 1st and best bet on finding the fault and a solution

    4. #3
      From my experience in the S40 misfire world (and I have plenty there on my old engine) - if you get a misfire strong enough to trigger a flashing CEL, it'll turn solid after the misfire's have ceased no matter what. If misfires start up again, it'll start flashing again, and cease when they cease. The light however, will stay on after the first one to trigger the flashing CEL. When I scan it, I either get Misfire Code One or Misfire Code Multiple Cylinders, and then the respective cylinders.

      These Volvo's are finicky, FINICKY creatures. They tend to do inexplicable and random crap for the pure reason of being able to do it rather than any other logical reasoning. According to some, there are knock sensors on our cars. According to others, it's a mathematical equation for firing vs expected torque/RPM increase for the cylinder and yours sounds definitely liek the latter of the two possibilities. That being said, sounds like you either had a coil or plug issue at that time that subsequently cleared itself up. Just my .02 get a scanner and see what it was. A CEL usually sets a nondescript ODBII code that can give you a direct hint, but you'll need a Volvo specific one to view the exact issue and the code set.
      2006 Volvo S40 AWD T5 M66 - Dusty Rusty
      2012 Subaru Outback 2.5i CVT - Slowmobile - CAI only, Powerstop Rotors+Pads.
      1996 HD Electra Glide - Big Bertha - 10:1 Wisecos; EV13 Cam: Ultima Digital Ignition; Buell Head Conversion; E85 Carb Tuned;

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    6. #4
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      Misfire is detected with the crank position sensor. Knock is detected with the knock sensors.
      2005 S40 T5 AWD automatic - Hilton stage 2+ with torque limit removal. Some mods: 3" DP & 2.5" catback, Do88 FMIC, Pumaspeed inlet plenum, ECU spacer.

    7. #5
      Global Moderator tmtalpey's Avatar
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      I haven't pulled DTCs with Vida but it will have to wait unfortunately.

      In the past this has happened to me when getting a bad tank of gas. On acceleration the car misses and the CEL flashes. It generally goes out when backing off. This is basically the meaning of a flashing CEL, or at least, "by the book" it is. If the CEL becomes steady, that's more serious. Of course, there were no messages in the DIM.

      The odd thing that happened here, I think, is that the car was (and is) perfectly fine, it just lugged pulling away from that one spot. However, the cylinder or cylinders didn't recover. I believe this is because the ECU shut one or more down, probably their injector(s). It sure felt like a zero in the impulse department on at least one. The car did continue to run, and was totally fine after a simple off/on.
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva Forge CBV, Elevate rear swaybar and torque mount, Snabb shift kit, etc.
      2016 XC60 T6 AWD
      1956 PV444 complete, running
      1956 PV444 very original, very rough

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