Cylinder #3 misfire

**Newby101** · 07-07-2011

Gentlemen, I need some HELP please!! Just bought a 2003 Grand Prix GT V6 3800 and she's misfiring on Cyl#3 code P0303. Or is it ???? Already replaced ignition module/coil pack, plugs, wires, injector and now valve spring and she's still knocking away.

Also having electrical issues with instrument cluster, fuel level fluctuating and temp rising. Fans do not seem to come on. Could these problems be conjoined somehow???? Man o' man I be confused.
It's a pretty significant knock at idle but goes away when driving.

**Jakescoots** · 07-07-2011

What about a lifter?

**BillBoost37** · 07-07-2011

You'd hear a lifter. It woudl be clacking loud.

Are you losing any coolant or got whitish exhaust?

**Zef_66** · 07-07-2011

Wait, so it's misfiring and knocking? Knocking isn't good at all. If it is a low end knock, you could have some internal damage going on.

I would recommend taking it to a good mechanic to listen to the engine and see if they think there is internal damage.

**blueguy** · 07-07-2011

Originally Posted by Newby101

Gentlemen, I need some HELP please!! Just bought a 2003 Grand Prix GT V6 3800.

Stop there.

Just take it back.

**Newby101** · 07-07-2011

Maybe it is a clack and not a knock?? My limited knowledge of engines will become very evident lol. Exhaust smoke isn't white but it is leaking very little from heater water bypass inlet. I removed the plug to see if it was getting steam cleaned but it looks perfect.When I put my ear to the upper intake on passenger side there is an erratic grinding sound. All the work that has been done (supposedly) was done by the guy I purchased car from. I just noticed the belt tensioner is bouncing around like a mofo. Man I wish I were smarter in this dept!! Thanks for all the help so far

**BillBoost37** · 07-07-2011

Ahhhh now we get more cluse.

Ok first thing I want you do is to check the firing order. And I mean definately follow every single wire the whole way.

Firewall
2...4...6

1...3...5
Radiator

Coil packs
3/6
2/5
1/4

On the coil, it doesn't matter which of the two posts the wire goes two because both fire at the same time. You can look at the top coil and have 3 or 6 hooked up to either of those posts.

It's sounding a bit like you have a couple wires crossed. Next up.. pull a plug and tell us what kind they are. If you arne't sure, take a pic and post it.

Get an overall pic of the motor too. We wanna see how clean and nice things are to see which wires are on it etc. Which coils..you get the point. Let's look this puppy over and get it running right.

**Newby101** · 07-07-2011

I'm on it like white on rice. Be a few minutes.
I still can't believe how awesome this forum and the people are. I'm geeked lol

**Newby101** · 07-07-2011

K, Everything is in the right place and order. However I'm unable to upload pics????? The plugs are Bosch Platinum. The wires are NGK (blue in color). I'm gonna try and figure out how to get the pics up in the meantime

**BillBoost37** · 07-07-2011

Originally Posted by Newby101

K, Everything is in the right place and order. However I'm unable to upload pics????? The plugs are Bosch Platinum. The wires are NGK (blue in color). I'm gonna try and figure out how to get the pics up in the meantime

You likely found the problem. If you are NA (I think you are?) pick up a set of non-Bosch iriduims or copper core plugs and give that a try.

For some random reason our waste spark ignition system kills Bosch plugs in a month or less. I recall seeing a writeup on Bosch's website about it at one time. WOTGTP had an issue.. less than a month old bosch double plats. A quick plug change and he was a semi happy camper (still had trans issues)

**matt5112** · 07-07-2011

motorking (honeywell guy) had a bit on that.

You should also stay away from using a copper core spark plug unless you really enjoy changing spark plugs. Your DIS ignition fires one half the spark plugs in the opposite direction, meaning the spark actually jumps from the side wire to the center wire. using any copper plug in a DIS ignition vehicle is a mistake that will cause rapid degradation in the sidewire and misfires in as little as 16k miles. Use the Autolite XP606 Iridium fine wire plug. Yes, they cost 7 bucks a piece. They are worth it. They take less ignition voltage to fire and have a 25% larger flame kernal than the stock plug. The also have a platinum button on the side wire to prevent gap erosion. They have a 100k life span as well. If I can answer any other questions for you, please feel free to contact me at Jay.Buckley@Honeywell.com

**Newby101** · 07-07-2011

Thanks guys, I'm gonna run out and grab some Iridium plugs on my way home tonight. Can I get away with just buying the one for test purposes or do I need replace all six right upfront???

**Zef_66** · 07-07-2011

Originally Posted by Newby101

Thanks guys, I'm gonna run out and grab some Iridium plugs on my way home tonight. Can I get away with just buying the one for test purposes or do I need replace all six right upfront???

You can just buy one and test it. But how are you scanning to tell you which cylinder is misfiring?

**Newby101** · 07-07-2011

I think it's an OBDII scanner. The code is p0303

**tayl5645** · 07-07-2011

So your not doing any active scanning your just going off from a code?

**Zef_66** · 07-07-2011

Originally Posted by Newby101

I think it's an OBDII scanner. The code is p0303

Do you clear the code everytime and the light goes off? Then it comes back on after running for a minute or two?

**Newby101** · 07-08-2011

Ya, like my post states I don't know much about engines (at all) but ya, no active scanning done. Never even heard about it LOL. Yes, everytime I clear the code, it comes back shortly thereafter. Will an active scan put an end to the guessing or just another fat chance at detecting the problem???