Hey guys, first tech question. Bought a G35 several months ago (Jan I think?) anyway, I haven't been using it the last ~2 months because it developed a miss and I was just using my bike. Now that I have time+ the weather is cooling down, I've been trying to fix it. Here's whats going on.


Background 2003 MT6 Coupe. ~130k miles.

Problem: Car has a miss on the center cylinder on the drivers side. This miss developed slowly over the period of a week. I changed the plugs in the hopes that would fix it and it netted me no result. Letting the car run a bit netted the cat get glowing red hot. This is probably due to un-burnt fuel finding its way into the exhaust (The plug on the center plug smells like fuel fyi)

Diagnosis: I discovered it was this cylinder when I pulled all the plugs and realized that one was covered in oil/fouled. I then proceeded to check other things.

Things I've done
1.) Compression test. 195-200psi across the board.
2.) Removed injector. Battery tested it, (clicking), back flushed it.
3.) Replaced coil 2x. Bought a used set of 6. No change when switching out.

I'm at a loss. Only thing I can think after dicking with it is that I somehow lost the cylinder (mechanically). Would a compression test not reveal that?

Thanks guys!

 

Do you have any check engine lights? If so what are the codes?

You can also perform a leakdown test which might provide more insight.

Usually a cylinder misfire is caused by loss of spark in the cylinder, bad air fuel mixture, and or loss of compression.

Your compression numbers look good, let me ask you this. Is the plug just wet or does it have carbon deposit build up, etc?

Give me a little more info on the spark plug. If the plug is just wet then I am still leaning towards your ignition system meaning that is not burning up the fuel. Did you check so that you are positive you have spark besides the fact of changing out the coil packs?

 

You should check to see if that cylinder's wiring to the coil is operational. The coil pack won't fire if it's not getting the signal to do so. I "think" you can pull the plug, attaching to the coil pack and hold the plug very close to something metal and see if the plug fires? Someone confirm that before he burns up his coild pack. lol

 

Thanks for the input guys. Made the most rookie mistake I could possibly muster; hooked two of the coils backwards (the ones in the back). Doh.

 

I don't think that should matter as long as it's plugged in to the wiring correctly.

 

Thats what it was. Dunno, how you label your banks, (if it was 4&6, or 3&5) but the connectors were going to the wrong coils.

Since I went into the problem w/ a miss, it just perpetuated the problem, so when I did all that work, it made it seem like it wasn't fixed.

 

i had the same problem but mine wasnt only just 1. i Have 2004 G35 Coupe. Kept going thru coils aFTER COILS. came to the conclusion it was my ECU, swapped it out and have been driving the car for 5 days straight without a coil burning or melting i would say. The only problem im having out of this now is the car not idling right. Any opinions? the other ECU i didnt have a idling problem i dont c y i would now maybe it wasnt programed right at the dealer. and planning on going back.

 

theres a diy for the idle reset on the site

 

At a most definate loss!!!!!!!!!
04 G35 coupe.
This is what I have done.
Replaced coils after coils to begin with
Regrounded all the grounds
Replaced my ECU/ Reprogramed
Had an idle problem and did a DIY cleaning of the throttle and butterfly, the car was running great except for 6th gear in which it Hessitated and then turns out burning another coil.
I have the check engine light on one is for the misfire. And the other is for the Cadillac converter which went bad after it glowed red from burning a coil previosly.
Please help really wouldn't like to let go of a nice G

 

Are you sure the coilpack is grounded properly? I pinched one og the grounds while doing my wire tuck and it resulted in a mis-fire.

While the car is at idle, reach in and touch the coilpack with your hand. If the idle becomes normal while you are touching it, its a grounding issue.