Cylinder 3 misfire. P0303

qwik48r · May 9th, 2008, 10:11 PM

02's....

MustangMatt96GT · May 10th, 2008, 12:34 AM

sounds like O2 sensors too me.

bigmike83 · May 10th, 2008, 10:10 AM

tell ya what when the car is running pull the plug wire off and see if i changes how the car runs at an idle. then report back

also
miles?

ujslost · May 10th, 2008, 04:00 PM

check your coolant level. sounds like to me there might be an intake leak getting to the spark plug hole and either fouling the plug or building pressure under the plug wire boot and blowing the wire off the plug or causeing it to crossfire to the aluminum head.

AFHockey1304 · May 12th, 2008, 11:53 PM

no all the gaskets in the motor are new...i have alot of bolt ons on my car.. I have BBK shorties, U/D pullies, TB, upper plenum, CAI, slp cat back with pypes O/R with high flow cats, ffrp 24lb injectors.. the oknly thing i dotn have is a Bigger MAF.. Could that cause the problem??/

AFHockey1304 · May 17th, 2008, 09:46 PM

no all the gaskets in the motor are new...i have alot of bolt ons on my car.. I have BBK shorties, U/D pullies, TB, upper plenum, CAI, slp cat back with pypes O/R with high flow cats, ffrp 24lb injectors.. the oknly thing i dotn have is a Bigger MAF.. Could that cause the problem??/

MustangMatt96GT · May 17th, 2008, 09:48 PM

is it tuned for the 24 pound injectors?

ujslost · May 17th, 2008, 10:40 PM

the only way you are getting a misfire on #3 cylinder is spark plug, wire, coil pack , water in plug boot, or faulty injector

MustangMatt96GT · May 17th, 2008, 10:42 PM

Originally Posted by ujslost

the only way you are getting a misfire on #3 cylinder is spark plug, wire, coil pack , water in plug boot, or faulty injector

+1

but it could run like crap without a tune for the injectors and it could be part of the running bad.

AFHockey1304 · May 18th, 2008, 05:18 PM

i dont have a tune or a bigger MAF? but it isnt throwing the misifire code anymore but it is still stumbling..idk what else could cause it..help/.

nes · May 18th, 2008, 06:36 PM

y do you have bigger injectors? esp with no tune?

AFHockey1304 · May 18th, 2008, 09:18 PM

i got the injectors because i was planning on tuned and didint want to tune it with out the bigger injectors...

AFHockey1304 · May 19th, 2008, 07:05 PM

on the two downstream oxygen sensors, wat are the colors you are supposto match up...i wonder if they are mismatced...would that cause it to run like crap????????

MustangMatt96GT · May 19th, 2008, 10:35 PM

the injectors are wat is making it run like crap. Put in the stockers to make it run and then put in the larger ones when you tune for it.

YOu will ruin the motor if you run those injectors too long without a tune.

ujslost · May 19th, 2008, 10:48 PM

oh shit dude if you have larger injectors you HAVE, I mean you MUST have the MAF replace or calibrated to match, thus a tune! Your flooding the hell out of the engine dude. WOuldnt surprise me if your oil doesnt smell like gas. I bet your washing the cylinder walls down. Put in stock injectors and change oil run engine 5 mins ,change oil again.

Casper98GT · May 21st, 2008, 11:46 PM

Originally Posted by ujslost
the only way you are getting a misfire on #3 cylinder is spark plug, wire, coil pack , water in plug boot, or faulty injector
+1

but it could run like crap without a tune for the injectors and it could be part of the running bad.

Hahaha. A Cylinder 3 misfire would be caused by alot. I will agree Plug, wire, coil pack or injector. But you could also have alot more. Bad piston rings from a washed down cylinder, could have a stuck valve. Maybe some carboned valves. You never know exactly what it is unless you do some diag on it.

Check compression in that cylinder you might be wasting youre time when you have a bad cylinder or valve. 19 to 24lbers...would make it run bad and as well as ruin youre cats and im thinking by now you would have a po420 or po430. I dont think youre doing much damage by running the 24's. the older fox'es with their shitty computers had a big problem trying to compensate for the injectors. But the new computers would adjust to a certain point. I would recommend a tune or a new MAF if youre planning on keeping them but i in no way think its the reason for a ONE cylinder misfire. The only thing that would happen from the MAF would set a rich code ( po171 but would also set po172 ) would set both due to both banks being rich. I dont understand the cylinder 3 thing. I would think it would set both those codes first. Maybe i dont know the entire story. I dunno.

MustangMatt96GT · May 21st, 2008, 11:49 PM

its no longer getting the misfire though... just running rough.

Casper98GT · May 21st, 2008, 11:53 PM

Getting any codes?

ujslost · May 22nd, 2008, 07:47 AM

Your right casper. I just stated the obvious causes of the p0303. Ya know how hard it is to diag online, especially if the owner doesn't know much about the vehicle or how it works. Everyone with a 96+ mustang or ford needs and IDS!!!!!! Wish I had a PDS myself.

Casper98GT · May 22nd, 2008, 07:54 PM

That would be awesome to have an IDS just laying around, haha..

So the owner of this thread ever check back ???? Are you just getting a po171/172....if you are. You need a tune, MAF or 19lb's back in the motor. Thats the cause. Plain and simple.

May 9th, 2008, 10:11 PM	#21
qwik48r Hardcore Enthusiast 08 GT Join Date: Jan 2008 Posts: 1,156	02's.... __________________ NObama '08 KEEP the 2nd amendment ALIVE!!! I've got a 2008 Mustang GT, Bolted w/ 4.10's. And a Drag Truck... LIFE IS GOOD!

May 10th, 2008, 12:34 AM	#22
MustangMatt96GT I Post Entirely Way Too Much 1996 Mustang GT 14.879@91.24 @ 5800 FT Join Date: Dec 2006 Location: Lakewood, CO Posts: 6,953	sounds like O2 sensors too me. __________________ We expect shit to break, look foward to realizing exactly when it is happening, and than obsess about dropping plenty of cash to rebuild stronger, so we can try to run it hard as hell and break again. We are sick individuals.

May 10th, 2008, 10:10 AM	#23
bigmike83 Regular 1997 mustang gt 8.06 at 87mph 1/8th mile on a 50 shot Join Date: Nov 2006 Location: clarksville TN Posts: 267	tell ya what when the car is running pull the plug wire off and see if i changes how the car runs at an idle. then report back also miles? __________________ 97 gt with 2004 pi motor,acufab intake and 75 mm bbk cold air kit,bbk long tube headers, off road h pipe,2 chamber flow, 3:73, diablo chip with dyno tune 269rwhp 301rwtq

May 10th, 2008, 04:00 PM	#24
ujslost MM Fanatic Join Date: Mar 2007 Location: Albertville, AL Posts: 3,725	check your coolant level. sounds like to me there might be an intake leak getting to the spark plug hole and either fouling the plug or building pressure under the plug wire boot and blowing the wire off the plug or causeing it to crossfire to the aluminum head. __________________ 1997 Mustang Gt Convertible for sale. Triple black, great condition and unmolested! http://www.moddedmustangs.com/forums...like-most.html

May 17th, 2008, 09:48 PM	#27
MustangMatt96GT I Post Entirely Way Too Much 1996 Mustang GT 14.879@91.24 @ 5800 FT Join Date: Dec 2006 Location: Lakewood, CO Posts: 6,953	is it tuned for the 24 pound injectors? __________________ We expect shit to break, look foward to realizing exactly when it is happening, and than obsess about dropping plenty of cash to rebuild stronger, so we can try to run it hard as hell and break again. We are sick individuals.

May 12th, 2008, 11:53 PM	#25
AFHockey1304 Newbie Join Date: May 2008 Posts: 18	no all the gaskets in the motor are new...i have alot of bolt ons on my car.. I have BBK shorties, U/D pullies, TB, upper plenum, CAI, slp cat back with pypes O/R with high flow cats, ffrp 24lb injectors.. the oknly thing i dotn have is a Bigger MAF.. Could that cause the problem??/

May 17th, 2008, 09:46 PM	#26
AFHockey1304 Newbie Join Date: May 2008 Posts: 18	no all the gaskets in the motor are new...i have alot of bolt ons on my car.. I have BBK shorties, U/D pullies, TB, upper plenum, CAI, slp cat back with pypes O/R with high flow cats, ffrp 24lb injectors.. the oknly thing i dotn have is a Bigger MAF.. Could that cause the problem??/

May 17th, 2008, 10:40 PM	#28
ujslost MM Fanatic Join Date: Mar 2007 Location: Albertville, AL Posts: 3,725	the only way you are getting a misfire on #3 cylinder is spark plug, wire, coil pack , water in plug boot, or faulty injector __________________ 1997 Mustang Gt Convertible for sale. Triple black, great condition and unmolested! http://www.moddedmustangs.com/forums...like-most.html

May 18th, 2008, 05:18 PM	#30
AFHockey1304 Newbie Join Date: May 2008 Posts: 18	i dont have a tune or a bigger MAF? but it isnt throwing the misifire code anymore but it is still stumbling..idk what else could cause it..help/.

May 18th, 2008, 09:18 PM	#32
AFHockey1304 Newbie Join Date: May 2008 Posts: 18	i got the injectors because i was planning on tuned and didint want to tune it with out the bigger injectors...

May 19th, 2008, 07:05 PM	#33
AFHockey1304 Newbie Join Date: May 2008 Posts: 18	on the two downstream oxygen sensors, wat are the colors you are supposto match up...i wonder if they are mismatced...would that cause it to run like crap????????

May 19th, 2008, 10:35 PM	#34
MustangMatt96GT I Post Entirely Way Too Much 1996 Mustang GT 14.879@91.24 @ 5800 FT Join Date: Dec 2006 Location: Lakewood, CO Posts: 6,953	the injectors are wat is making it run like crap. Put in the stockers to make it run and then put in the larger ones when you tune for it. YOu will ruin the motor if you run those injectors too long without a tune. __________________ We expect shit to break, look foward to realizing exactly when it is happening, and than obsess about dropping plenty of cash to rebuild stronger, so we can try to run it hard as hell and break again. We are sick individuals.

May 19th, 2008, 10:48 PM	#35
ujslost MM Fanatic Join Date: Mar 2007 Location: Albertville, AL Posts: 3,725	oh shit dude if you have larger injectors you HAVE, I mean you MUST have the MAF replace or calibrated to match, thus a tune! Your flooding the hell out of the engine dude. WOuldnt surprise me if your oil doesnt smell like gas. I bet your washing the cylinder walls down. Put in stock injectors and change oil run engine 5 mins ,change oil again. __________________ 1997 Mustang Gt Convertible for sale. Triple black, great condition and unmolested! http://www.moddedmustangs.com/forums...like-most.html

May 21st, 2008, 11:49 PM	#37
MustangMatt96GT I Post Entirely Way Too Much 1996 Mustang GT 14.879@91.24 @ 5800 FT Join Date: Dec 2006 Location: Lakewood, CO Posts: 6,953	its no longer getting the misfire though... just running rough. __________________ We expect shit to break, look foward to realizing exactly when it is happening, and than obsess about dropping plenty of cash to rebuild stronger, so we can try to run it hard as hell and break again. We are sick individuals.

May 21st, 2008, 11:53 PM	#38
Casper98GT Hardcore Enthusiast Join Date: Aug 2005 Location: NEW HAMPSHIRE Posts: 2,354	Getting any codes? __________________ Ford/Toyota tech. -93 LX, X303 heads, F-cam, Trickflow u/l, 1.6 RR, FR wires, MSD cap/rotor, Elec. fan, a/c delete, smog delete, sn95 fuel rails with BBK regulator, 75mm TB and EGR, Vortech S-trim w/intercooler, 42lb inj/PMAS, 3.55's -

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May 22nd, 2008, 07:47 AM	#39
ujslost MM Fanatic Join Date: Mar 2007 Location: Albertville, AL Posts: 3,725	Your right casper. I just stated the obvious causes of the p0303. Ya know how hard it is to diag online, especially if the owner doesn't know much about the vehicle or how it works. Everyone with a 96+ mustang or ford needs and IDS!!!!!! Wish I had a PDS myself. __________________ 1997 Mustang Gt Convertible for sale. Triple black, great condition and unmolested! http://www.moddedmustangs.com/forums...like-most.html

May 22nd, 2008, 07:54 PM	#40
Casper98GT Hardcore Enthusiast Join Date: Aug 2005 Location: NEW HAMPSHIRE Posts: 2,354	That would be awesome to have an IDS just laying around, haha.. So the owner of this thread ever check back ???? Are you just getting a po171/172....if you are. You need a tune, MAF or 19lb's back in the motor. Thats the cause. Plain and simple. __________________ Ford/Toyota tech. -93 LX, X303 heads, F-cam, Trickflow u/l, 1.6 RR, FR wires, MSD cap/rotor, Elec. fan, a/c delete, smog delete, sn95 fuel rails with BBK regulator, 75mm TB and EGR, Vortech S-trim w/intercooler, 42lb inj/PMAS, 3.55's -