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P0300 code - 2003 Pontiac Montana
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angusranch
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Jan 15, 2014, 6:09 AM
Post #1 of 31
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P0300 code - 2003 Pontiac Montana
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Have a 2003 Pontiac Montana van 3.4 motor,122000 miles.P0300 code and costant misfire on #1 cylinder
(This post was edited by carjunky on Jan 16, 2014, 4:34 PM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Jan 15, 2014, 7:03 AM
Post #2 of 31
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You likely have misfires on other cylinders besides #1 because of the random misfire code. Coils, plugs and wires are the most common causes but do a compression test to make sure the cylinder is healthy.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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angusranch
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Jan 15, 2014, 8:59 AM
Post #3 of 31
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I have put in new plugs,wires and coilpacks.Thought problem might be bad injector on #1 cylinder so put in new factory injector.SES light still flashes when you hit 30 MPH.Will put on compression tester to check cylinder.Any other ideas?getting to be a royal pain.Could it be a burnt exhaust valve?Obi-codes said could be burnt valve or cataylic convertor possibly.Any help appreciated.Thanks.
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Hammer Time
Ultimate Carjunky
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Jan 15, 2014, 10:07 AM
Post #4 of 31
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You should have been testing the spark before replacing all those ignition parts. Looking at the condition of the plugs should tell you a lot about the fuel issues too.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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angusranch
User
Jan 15, 2014, 10:14 AM
Post #5 of 31
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I will check compression on #1 cylinder.Put in new bosch plugs.Spark looked good before on 1.rEven though it is p0300 code all problem seems to be on#1 cylinder.Spark looks good on all other cylinders.
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kev2
Veteran
Jan 15, 2014, 11:00 AM
Post #6 of 31
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THe flashing Ck eng Lgt is an indicator of likely damage to catalytic converter,
want to be sure you -
>check that #1 inj is pulsing - use a noid light..
> as mentioned #1 plug - wet dry, black tan, might be a hint.
>do a fuel pressure test - and fuel press leak down test.
> check the FPR (fuel press reg) - remove vac line to FPR there should be NO evidence of fuel.
then a compression test- I think something mentiond above was missed
FYI: no to the bosch plugs, use AC DELCO, to late I know but for others and future - can cause p0300.
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Hammer Time
Ultimate Carjunky
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Jan 15, 2014, 12:28 PM
Post #8 of 31
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Yeah, I missed that one Nick. Those Bosch plugs HAVE to go. They are junk in that engine.......... seriously.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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nickwarner
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Jan 15, 2014, 12:49 PM
Post #9 of 31
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You're safe HT. He didn't post the brand name till after you had posted. Stood out to me when I was reading through the thread.
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angusranch
User
Jan 16, 2014, 12:07 PM
Post #10 of 31
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Is fuel pressure regulator hooked into fuel rail?Will get noid light to check injector.
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nickwarner
Veteran
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Jan 16, 2014, 12:26 PM
Post #11 of 31
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The regulator is in the fuel rail. Looks like this. The little nipple on the top is where a vacuum line hooks up. If the diaphragm inside it is bad you'll see fuel in the line. Pull the line off and cap it with your finger while the engine is running and watch it for a minute. If anything comes out of the regulator hole you know it is bad. Part is about $50 and fairly simple to fix. If it allows fuel through it, it drops extra fuel into the engine and runs bad. If bad enough it can stall you out because it will run incredibly rich especially on the rear cylinders where the vac line goes into the intake. Has one that couldn't even move once and it also destroyed the catalytic convertor because of all the raw fuel it was dumping.
 
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angusranch
User
Jan 16, 2014, 8:25 PM
Post #12 of 31
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Will check it out in morning.Put scanner on again now shows 1 & 3 misfiring.Also SES light is flashing when idling now.
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Discretesignals
Ultimate Carjunky
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Jan 16, 2014, 9:17 PM
Post #13 of 31
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As the others stated means you have catalyst damaging misfires going on. Try not to run the engine too long with a flashing light cause your catalyst is getting hammered. If you really need to run it for a long period of time to figure out what is going on, you really should take off the cat and put a test pipe in its place. A good tech, should be able to figure out what is going on fairly quickly.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jan 16, 2014, 9:21 PM)
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angusranch
User
Jan 17, 2014, 7:47 PM
Post #14 of 31
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The fuel regulator checked out fine .No leaks.No fuel coming out.Switched plugs to Ac Delco.Fuel pressure red 58 running .54 when motor was shut off.Compression on #1 read 160.checked #3 it read just over 180.I have seen aliitle antifreeze behind power steering pump byintake manifold.Looked like it was coming from back.D o not know if possible head gasket leak if #1 read lower then3.Do not know what normal compression should be.Will hook up computer to see what it says.
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angusranch
User
Jan 17, 2014, 8:14 PM
Post #15 of 31
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Just put computer on.1 and 3 are still misfiring constantly.
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Hammer Time
Ultimate Carjunky
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Jan 18, 2014, 3:35 AM
Post #16 of 31
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The only thing that 1 and 3 have in common is that they are adjoining cylinders so make sure the wires aren't crossed. You may have to do a leakdown test to determine if there is any head gasket damage between them but I kinda doubt it. It could end up being an injector problem but you will have to do some spark testing to determine if you're dealing with a spark or fuel problem.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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kev2
Veteran
Jan 18, 2014, 10:59 AM
Post #17 of 31
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have you used a noid light - pulsing, on steady?
fuel pressure held 54psi - To be clear, take pressure with engine running, then engine off key in RUN position KOEO, we want the inj circuit energized to see if a problem.
How do those plugs look - yes new but maybe a hint.
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angusranch
User
Jan 18, 2014, 11:54 AM
Post #18 of 31
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Did not use noid light.Only way I see to use noid light is to take air ram off.Ordered an electronic stethoscope to check injectors.Will that work?KOEO?Key on engine on?
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Tom Greenleaf
Ultimate Carjunky
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Jan 18, 2014, 12:04 PM
Post #19 of 31
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KOEO = Key On (run position) Engine Off........... T
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angusranch
User
Jan 18, 2014, 12:06 PM
Post #20 of 31
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Ok Thanks
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Hammer Time
Ultimate Carjunky
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Jan 18, 2014, 12:43 PM
Post #21 of 31
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You can't plug the bulb directly into the injector but you can use jumper wires and tap into the wires at the harness before it goes under the manifold. Use power directly from the battery. Just don't plug it in until you are ready to test it because the injector may stay on if it's powered directly to the battery.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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angusranch
User
Jan 18, 2014, 8:54 PM
Post #22 of 31
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fuel pressure at 54 when runnning.When turn off and turn key on pressure holds at 60.Bought an ignitionmate tester for voltage.Good voltage going through plug wires.Do not know how accurate this is but another mechanic on youtube ase certified used a stethsoscope to listen to injectors.All sounded like they had a steady pulsating.Do not know if this is very accurate or not.
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Hammer Time
Ultimate Carjunky
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Jan 19, 2014, 7:33 AM
Post #23 of 31
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There is one very important question here ................. Was the misfire present at the moment you performed these tests?
You have to be observing the ignition at the moment this problem occurs.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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angusranch
User
Jan 19, 2014, 11:09 AM
Post #24 of 31
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Ye they were.
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angusranch
User
Jan 19, 2014, 9:31 PM
Post #25 of 31
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Took out plug.Looked like a little wet but white.It has a good blue spark.If injector is not sending fuel to cylinder possible short in wiring?Put in new factory injector prior to this.will try to check wiring to injectors.
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