Help! On vacation, car throwing cylinder 3 misfire code. Wiggled some wires and seems to be working for now, but I don't trust it and need to drive 20 hrs on Monday to get home. I have access to some relatives' tools. Anyone have ideas?

'03 ls with 3400 engine. Spark plugs and wires were replaced about 30,000 ago.

 

Oddly, I'm tracing down a similar problem on a 2000 Grand Am. I believe the code it's throwing is P0303.
I'll give you stuff I have gone through on the Grand Am:

Some people say it's the coil (as a tower on the coil may be failing). Doubtful, not impossible. A way to test it, swap the wires on that coil (#3 and #6 I believe share the same coil). The coil fires both plugs at the same time, if your problem moves to another cylinder, it's the coil.
I found my issue, not a coil.

I removed and inspected the plug. It's fairly new (I'm guessing 5-10k miles on this set), it was not wet but smelled heavy of fuel. Cleaned it, re-installed.

Along the way, the car has thrown a P203, an issue with the injector. I'm 90% sure, I have a bad #3 injector. Inspected plug wire, no issues found (also newer wires).

I did find a rubber cap on a non-used vacuum line had dry rotted. This is a port on the UIM, facing the alternator. For now, the cheap fix from my garage (far from my best work), piece of tubing with a bolt in it. This has yielded a noticable improvement.

Swapped the #3 plug with a front plug (just to see if the problem follows the plug.

At this point it went from a daily problem (one day an entire ride to work mis-fire the entire way) to every other day a hicup for a minute, but now that hicup is LIGHT compared to the original issue.

Speculation, vac leak caused problems that were noticable in the #3 cylinder more then anywhere else. Injector may have "dirtied" itself (guessing). But if problem persists, I think it's new #3 injector time.

 

Hmmm...well it's behaved itself through an entire day of light driving. I'm going to run some injector cleaner through it for now and hope for the best. It's only done it for about an hour total so far. I've never had the plugs out of this car and having a bit of trouble figuring out how to get to them. I'll probably take those out and have a look, possibly just change them since it's a cheap thing to do anyway.

And yeah the code you gave is what I had too. I cleared it for now and so far no issues. I'll keep you updated but I had a panic moment since were 1000 miles from home and cannot leave any later than tomorrow early morning.

 

As a side note, car keeps telling me to change the oil even tho I just did. The key on and press accelerator 3 times trick isn't clearing it. Doubt it's related but still.

 

The oil life and misfire, no relation.

As for the plugs, they are EASY EASY on the 3400. I don't think I can get much of a look on the back ones, but I do pretty well by feel. Doesn't take long.

 

Yea-they look like they should be easy but can't find where to loosen them. I think there are aftermarket wires on there covering them up. I didn't install the plugs that are in there now so will have to experiment.

Car has now gone about 200 miles with no misfires. Of course, also had my HIDs go out. Crazy vacation!

 

I'm a little lost about the aftermarket wires issue. Got a pic of what you're looking at?

 

Admittedly it's hard to see, but where the wire goes into the engine there's a rubber bit around it:

dRxtCIzl.jpg

 

All I see are regular wires. All plug wires have a "boot" on the end and it slides over the plug (the boot shields the connection). All you have to do is grab the boot and give it a twisting motion while pulling it back and it should disconnect from the plug.

Even though new wires come pre-greased, a little extra die-electric grease is worth while.

 

Well now I feel ridiculous. Never seen that on spark plug wires before. Was afraid to go yanking on it too much.