Rough idle on my S60

moonweasel · Post by **moonweasel** » 26 Sep 2017, 13:15

So I know this could be one (or more) of many things, but just hoping you good folks here might be willing to help guide a newcomer to the likely culprits.

My car is a 2002 S60, base trim (2.4L, NA). It recently started running choppy — idle resting around 800–900rpms, and sounding like it was going to die, but smooth when revving.

CEL was on, and I pulled codes with a little OBDII reader: evap leak (gross) and cylinder 2 misfire.

What I've already done:

replaced gas cap to remove evap leak from equation — this successfully removed that code.
replaced spark plugs to see if that was causing the misfire (#2 indeed looked burned out), but no change to the rough idle.
pulled ETM: it was definitely dirty; I cleaned it with throttle body cleaner and a brass brush and reassembled (with a new gasket).

While I was working on the ETM I noticed that a vacuum line was hanging loose: the one that comes out of the back of the air filter box and goes into the front of the intake; the little rubber coupling/elbow had crumbled. Also, one of the three clips that latches the air box is missing — I ordered replacement elbow and clip online, as I couldn't find any in town.

In the meantime I did try duct taping the vacuum line directly to the nipple on the intake just so I could reset the codes and see what happened: engine revved up to probably 1500 or 2000, then settled a little over 1000, and seemed to be running a lot better… still some sputters, but no longer sounding like it was going to die. Then the CEL came back on: cylinder 2 misfire again.

So, my question while I wait for the airbox/vacuum line parts to show up: could those be the culprit for the misfire? or should I move on to checking ignition coils and/or fuel injectors while I wait? and/or what else should I be looking at?

zjevik · Post by **zjevik** » 26 Sep 2017, 16:39

I don't think that the evap leak would give to a misfire on one cylinder only but I might be wrong. I would try to switch coils around (switch the ignition coil from cylinder 2 with another cylinder) and see if the code for misfire will follow the coil or not. You should be able to test this relatively fast since you already took the top engine cover off to change the spark plug.

I'm sure abscate or someone more experienced than I will give their opinion soon.

moonweasel · Post by **moonweasel** » 26 Sep 2017, 21:25

Thanks Zjevik! I will try swapping the ignition coil in the morning and update.

Post by **abscate** » 27 Sep 2017, 05:15

That abscate guy is good for snark but wait for some real mechanics for advice.

That loose small hose/elbow is vacuum for the air cleaner temperature door ( vacuum for the manifold goes up the the air cleaner, through a thermostat (the double nipple thing on the pack of the air cleaner) then back down to the door on the bottom of the air cleaner) probably won't cause a rough idle. If one elbow went, buy three more as they are probably all crumbly.

If just one plug looks bad, either swap or buy one coil and try replacing. I would say you have a 95% success probability. Fuel injection on this car is really reliable.

I hope no one notices I nested parantheses which is an MVS violation, although not as bad as using words like "Forums"