#2 Cylinder Misfire???
 

So, I had a diagnostic done on my car the other day. It came up with a code #2 cylinder misfire. The car is running real rough when idle, and when accelerating at from low speeds. On the highway it runs smooth. We changed the spark plugs, and also tried putting injector cleaner in the gas tank with no success. Any other easy fixes or suggestions? The intake gasket was replaced in February and the fuel pump and fuel filter were replaced in November. I have about 102,000 miles on the car. It is the V6 3400 Olds Alero.

Test for spark at the coil pak located near the FW. If spark good check Fuel pressure (Port fitting near the belt), if pressure @ 52-59 psi) then check compression on #2 cylinder (1st piston near near belt by radiator) min 100psi.
if good check injector for pulse using led diode.

If all else fails check for coolant in cylinder. If coolant found check for LIM leak. If LIm is good be prepared for 4 digit bill.

any other codes first besides P0302?

Maybe P0420???

That is the right steps and in the right order. My best guess right now would be a bad coil or wire. Check the wire first.

lol did ya put the wires on the right plugs?

It wouldn't be a miss localized on #2 then. There would be at least two cyls misfiring.

I've only got those two codes.

I replaced the wires about a year ago. So I don't think that is it.

They were pulled one at a time, so yeah they are in the right spot. Thanks though!

super white alero...where did you get those specs on fuel pressure? the info I have says "With the ignition switch "ON" and the fuel pump "RUNNING", the fuel pressure indicated by the fuel pressure gage should be 284-325 kPa (41-47 psi)." You're right about the compression, shouldn't be lower than 100 psi.

keri_anne, when you changed the plugs, did #2 plug look any different from the rest? You can check spark at the plug end of the #2 wire, then check it at the coil. If you have spark at the coil but not the plug end, then you have a bad wire. Tempting as it is, don't overlook the simple things! Wouldn't be the first time a wire has gone bad in less than a year. The plug end of the wire on my Jeep recently came apart inside the rubber boot and it was less than a year old.

All in all, I second (or third) the advice so far. Good luck tracking down that problem.

Thanks much Surreal! There is spark at both ends of the wire though. I'm like you though, check the "cheap" stuff first and then move on up! Hopfully not up too far though. I've been trying to sell the car! Guess I can't sell it like this! Thanks again.

Is there a loud knock aside from the miss? My bro's car did this, turned out to be a loose rocker. Pulled the valve covers and retorqued and it was fine. Lucky it was an intake rather than an exhaust.

AllData online -

those are the spec for KOEO. The spec you place is for KOER

i could elaborate more if you like on deadpaning and isolating the cause but you need more specialized tools. Keri just check those first. i rule out, ignition module since you have only 1 cylinder. Im lead to believe you need only 1 coil pak. Easy way to check is to swap the coilp with the other two and see if the misfire goes to the other cylinder.

No loud knock.

Hrm...ok...gotcha. I got my info from AllData too. I didn't see the specs you provided on AllData. But it makes sense that the pressure would different for KOEO vs KOER.

What 2 codes the ones I pulled from my butt? you mean an P0420 - Catalyst below threshold and P0302-#2 misfire?

You can't have a P0420 and a localized misfire.
Please have AZ provide a scan with codes. Look specifiy for something that say "ignition circuit" or "lean condition" or "out of range"

Those are the two codes that the mechanic gave me. I didn't realize you were just guessing! I just thought, wow this kid knows what he is talking about! The slip specifically says Code P0420 catalytic Convertor not working properly and code P0302 Cylinder #2 misfire.

K, forget the cat code first isolate the misfire first. A cat below threshold and misfire could be relate but very rarely. a serious misfire could damage the ceramic material in the pipe.

Do the following as explained in previous steps. Clear code, drive @ steady 55 for 3 miles, make sure the engine experiences a 60* change in temperature. If P0420 comes back, or engine has no get up till about 3000rpm, confirm cat problem by removing the O2 before the cat and retest.

Mind you I'm no expert.... but could it be as simple as having the timing adjusted?


Oh, And if this was the case, I'm assuming there would be lights flashing all over the dash from a misfire right?

The car is all better! It was a loose bolt on one of the pistons. That is what I think he said anyway. Or a loose bolt on one of the heads. Anyway it was a $3.00 fix!!

Rocker arm bolts huh? glad you got it fixed.