P0303 Cylinder 3 misfire

[Krule]

99 Grand prix Gt
DTC p0303

I've changed:

ICM - 6/3 coil pack - #3 plug / wire

What else can be related to this issue?

Thanks.

[richtazz]

next on the list of things to check is the #3 fuel injector and compression on that cylinder.

[Krule]

Originally Posted by richtazz

next on the list of things to check is the #3 fuel injector and compression on that cylinder.

alright i've never actuatly done these checks, how would i go about doing so? and if the compression does end up being very low what can i possibly do about it? thanks

[Mickey#1]

You can swap #1 & #3 injector, if the misfire moves to #1 then you know the injector is bad/dirty. You could try checking the resistance with an ohm meter before swapping them. Are you loosing any coolant?

You'll need a gauge to check compression.

[Krule]

Originally Posted by Mickey#1

You can swap #1 & #3 injector, if the misfire moves to #1 then you know the injector is bad/dirty. You could try checking the resistance with an ohm meter before swapping them. Are you loosing any coolant?

You'll need a gauge to check compression.

Alright, don't have a gauge to check compression, my buddy has a shop he might have something. whats the resistance supposed to be on the injector's? and do i have to depressure the lines before pulling them off? and im not exactly sure which is #1 / #3. Coolant seems to be ok, as far as i can tell im not losing any. nothing in the oil thats for sure. Thanks

[Mickey#1]

Standing in front of the car & looking at engine, #1 is front left #3 is front middle.
2 - 4 - 6
^back cylinders
1 -3 - 5
^front cylinders

Check the resistance of all 6 injectors. All the readings should be close. If you're not sure then post the results. I'd go ahead & relieve the pressure although it really doesn't matter. Just don't start the car until the gas has evaporated.

[Krule]

Originally Posted by Mickey#1

Standing in front of the car & looking at engine, #1 is front left #3 is front middle.
2 - 4 - 6
^back cylinders
1 -3 - 5
^front cylinders

Check the resistance of all 6 injectors. All the readings should be close. If you're not sure then post the results. I'd go ahead & relieve the pressure although it really doesn't matter. Just don't start the car until the gas has evaporated.

alright awesome thanks, i was assuming they were located over the cylinders. i gota headout for lunch right now so ill be sure to do it asap. Also can a cylidner misfire be related to a transmission probelm? tranny currently has 400k+ on it, ill check the fluid to see if it's ok aswell.

[BNaylor]

To check fuel injector coil resistance you do not need to depressurize the fuel supply system. The injectors are located on the lower intake manifold port runners on a NA SII 3800. All you have to do is remove the electrical connector to each fuel injector. Typical reading is around 11-12 ohms and all should be close to each other. Anything lower or higher the injector is suspect.

Another check before replacing or swapping the injector is to run a noid light test to make sure the PCM fuel injector pulse width modulation to that cylinder is good or you can use a DMM. The reading will be high most of the time and then pulse low for a split second.

[Krule]

Originally Posted by BNaylor

To check fuel injector coil resistance you do not need to depressurize the fuel supply system. The injectors are located on the lower intake manifold port runners on a NA SII 3800. All you have to do is remove the electrical connector to each fuel injector. Typical reading is around 11-12 ohms and all should be close to each other. Anything lower or higher the injector is suspect.

Another check before replacing or swapping the injector is to run a noid light test to make sure the PCM fuel injector pulse width modulation to that cylinder is good or you can use a DMM. The reading will be high most of the time and then pulse low for a split second.

alright im assuming this method would work?

http://wiki.answers.com/Q/How_do_you...e_if_it_is_bad

My fathers saying the probelm is more then likely an emission probelm because i get a Red on our OBD 2 scanner. I also changed the egr valve, anything else thats related to this? God i wish it was something simple with this car for me but it never is.

I need something like this to happen:

http://www.youtube.com/watch?v=npTRX...eature=related

[BNaylor]

Most engine related DTCs are emissions related problems. Any fixed or random misfire DTC will cause a red flag on IM readiness and it will most likely fail emissions testing until corrected. Work on ruling out the fuel injector and go from there.

[Krule]

need i say anything more.. probelm solved. Never changed the plug just cleaned it, guess it just cracked. atleast i paid nothing for parts because i got my other engine still :P. Injectors all read 12.

Thanks guys

[Krule]

omg.. well the symptions are back again. plug is fine compression on all cylinders is 180, injectors all give out 12, switched other a good wire / 6/3 coil pack / ICM. What else can this be related to? i mean it is giving me the p0303 code.. GR! tranny has about 405k on it, engine has 160k. Baiscally when i hit the floor with the pedal the car gets stuck and wont shift up at a certain point (once it hits about 5-6k rpm) almost and it knocks bad. sometimes going up hills it'll start banging and i can feel the power lost, it's completly random at this point, doesn't even happen all the time.. can this me a tranny probelm? or cat converter? seems to happen mainly between 80-100km. Had almost this exact issue with my 99 engine and it was the timing chain, but it feels different this time, like before the car would surge, now it's banging; no way it's the timing chain.

[tblake]

If you have a P0303, Figure that out before going any further. I would pull that plug out and see if its cracked again.

Seems like I remember another forum member having problmes with AC delco plats that kept cracking in a specific cylinder.

[Krule]

Originally Posted by tblake

If you have a P0303, Figure that out before going any further. I would pull that plug out and see if its cracked again.

Seems like I remember another forum member having problmes with AC delco plats that kept cracking in a specific cylinder.

i checked it out again, used a spray bottle of water at night and saw sparks coming from that #3 plug. changed the wire, while doing so noticed the spark plug is cracked again. jesus.. i dont get it? thats 2 in a row within a week from each other.. There OEM plugs!

[BNaylor]

Are you using new plug wires and spark plugs or just switching out old parts between the two motors? Also, are you using the metal heat shields?