Cel P0303

[vpcar]

Hello everyone,

My 2002 C4S got it's first CEL a couple of days ago. I haven't been able to go in the garage and look at it till today.. Here's what happened, I woke up to start the car as normal and got a blinking check engine light and rough idle. I hooked the reader up and got a CEL P0303 misfire cylinder 3. I've read the posts about checking the plug and coil pack on cylinder 3 which I did. Here is a picture of the plug and coil that I replaced 6 weeks ago. I here other posts mentioning bad MAFS or stuck variocam. Anyone have any ideas? The car has been running just fine even as it was pulled into the garage the night before this happened. I have what also looks like a leaking variocam solenoid next to that cylinder. Could that be the root of the problem? See pic.

[RFM]

Vario Cam Plus (valve lift) engines are suffering every now and than with a defective valve lifter (stuck in full lift or minimum lift). This problem indicates a "misfire code" let check that out first.

[vpcar]

Thanks for the advice. How do you check that? Here is an update of what I've done.

I didn't mention previously I did a visual inspection of the coil pack and plug on cylinder 3 and didn't swap the plug/coil with another cylinder as suggested in another post. So I was going to have the car flat bed to Hoehn to get it checked out . Well, yesterday I disconnected the battery to reset the values/clear code, swapped out bank 3 with bank 1to try and rule out a spark issue. Spark plug wire was going to be next (they're originals). I fired the car up and didn't get a cell. Idle was much better with the exception of an intermittent pop/sputter from the exhaust. Took the car for a test drive and I could tell the car was misfiring with slight loss of power. Brought the car back to the garage and took the coil pack from cyl1 that was originally on cyl 3 off and replaced it with an old one. Fired the car up test drove it and wow! smooth idle, no code, and no back fire/w power restored. I'm hoping it was just a bad or failed coil pack. What made me think of swapping the old coil for the new was, I bought my coil packs supposedly new from a guy on Ebay to save a couple of bucks and I think I got swindled. Lesson learned there or just a bad one? I don't know. Is there a way to test the suspect coil pack? Going to keep monitoring to see if the issue returns.

Anyway, sorry for being long winded just want to be helpful with some simple trouble shooting I was doing for others who may have or will be experiencing the same problem.

Just sharing, but here's a picture of my car after today's test drive.

[RFM]

A defective "new" coil is possible, if the issue stays away within a week or so, it should be OK.

[tampa996]

I know this thread is ancient, but I stumbled across it while I was researching an issue I am currently having so I figured I would provide an answer to Ops question.

Quoting Loren:

There is a simple test for the coils to see if they are good or not. All you need is an ohm meter.

Coils:

Resistance between terminal 1 and terminal 15 at 20°C: 0.3 - 0.7 ohms.

Anything outside of this range is suspect.

Likewise on the spark plug connectors:

Resistance: approx. 2 k ohms

[JFP in PA]

I know this thread is ancient, but I stumbled across it while I was researching an issue I am currently having so I figured I would provide an answer to Ops question.

Quoting Loren:

There is a simple test for the coils to see if they are good or not. All you need is an ohm meter.

Coils:

Resistance between terminal 1 and terminal 15 at 20°C: 0.3 - 0.7 ohms.

Anything outside of this range is suspect.

Likewise on the spark plug connectors:

Resistance: approx. 2 k ohms

One potentially misleading issue with static resistance testing: Coils often test fine on the bench, but then break down electrically under hot load conditions. So if the unit is suspect, test it on the bench, but then swap it with a another coil pack from the engine that is working correctly and see if the misfire moves to that cylinder. If it does, the coil pack is toast.