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Posted on Dec 17, 2017
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2003 GMC full size truck, check engine light stays on. Engine has a constant miss. New plugs and plug wires have been installed, intake manifold gasket has been changed. Nothing has helped.Exhaust has been checked. All has been checked with GM computer, It always says intermediate missfire. Need help, miss is bad.

  • Ray Keckeisen May 11, 2010

    check the mass air flow sensor and the hoses leading to it make sure something is not blocking air flow, what is the code you are getting

  • Richard Faber
    Richard Faber Dec 17, 2017

    Could be a bad coil. In rare cases the engine computer could be faulty

×

1 Answer

Rj Right

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  • Expert 157 Answers
  • Posted on Dec 17, 2017
Rj Right
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Joined: Nov 13, 2013
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Chev is known for injector issues. You may have to remove the intake plenum and change one or 2 of the injectors. You can find them reasonably cheap online. You can test individual injectors with a small square 9 volt battery - never use a 12 volt car battery on electronic components as it's too much amperage.

5 Related Answers

emissionwiz

Marvin

  • 85242 Answers
  • Posted on Oct 21, 2008

SOURCE: need how to find TDC on 4.3 v-6

Remove # 1 plug and stick your finger in the hole, roll the engine over by hand, when you start to feel pressure in the cylinder you are near TDC, just check the crank pulley marks to zero it to TDC mark on pulley.

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Anonymous

  • 3 Answers
  • Posted on Jan 15, 2009

SOURCE: check engine light 2004 GMC Yukon

When my check engine light went on, it was a oxygen sensor

Anonymous

  • 33 Answers
  • Posted on Mar 27, 2009

SOURCE: 1995 Buick Park AV intake manifold gasket starting to leak

THIS IS VERY COMMEN IN FACT JUST ABOUT EVERY SINGLE 3.1AND 3.4 AND 3.8 EVER MADE BY CHEVY LEAKS AT THE LOWER INTAKE ALL OF THEM AND USEALLY STARTS AT ABOUT 50000 MILES THE PARTS COST ABOUT 300.00 AT THE DEALER FOR NEW GASKETS AND COOLENT AND SEALENT ALL THE PARTS YOU WILL NEED THE PROBLEM IS ITS ABOUT A SIX HOUR JOB SO THE LABOR KILLS YA BUT IT IS ALOT OF WORK BUT THE GOOD PART IS THERE IS NO NEED TO REMOVE THE PUSH RODS ON A 3.8 LIKE YOU DO ON A 3.4 I CAN GIVE YOU THE STEPS IF YOU LIKE BUT THIS JOB IS BEST TO SEND TO A MECHANIC AS IT HAS A LOT OF LITTLE THINGS THAT MUST BE DONE OR YOU CAN MAKE A BIGGER MESS THEN YOU GOT ALREADY... HOPE THIS WAS HELP FULL LET ME NO IF YOU NEED MORE INFO

Anonymous

  • 35 Answers
  • Posted on May 31, 2009

SOURCE: How to install intake manifold gaskets and their location.

go to autozone.com and register free then select make year ect.
select repair info (you have to register 4 this)
step by step and photos!!!!

mkv0525

Mike Vincent

  • 358 Answers
  • Posted on Jun 12, 2009

SOURCE: I have 96 gmc 350 vortec. missing really bad. Ive

ou need to check compression on all the cly. do you know which cly is dead?

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2004 GMC Envoy misfire

If you pull the #2 plug out and start the engine do you see a spark? You didn't mention if you checked the wires or not, but it could be a bad plug wire. If there is a spark, I'd try and see if the #2 injector is actually firing like you mentioned above.
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Hi Allen, The brake booster is connected to the intake manifold and that is where the low pressure is generated. If the diaphragm or one way valve, or connection pipe is leaking it will give the same effect as a leakage on the intake manifold. The symptoms you report are of a leakage on the intake manifold. To prove one way or another, disconnect the vacuum pipe for the booster and block the connection into the intake manifold. Be careful when testing as you will need to use excessive force on the brake pedal to stop. If the symptoms disappear fit a new booster, if not, pour water along the manifold and observe any bubbles where there may be a leakage. Let me know how you get on. Regards John
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I have a 2003 GMC Savana van. It is missing at an idle on #1 and #3 cylinder. I've changed the coils and injector, plugs and wires and nothing has fixed it yet. What is the problem?

Have you tried looking at the intake manifold gasket? at idle it will misfire, under higher engine speeds it will go away. Also look for a vacuum pipe split/perished. I use brief bursts of brake cleaner to find manifold airleaks around the joint between the manifold and engine block. If you attempt this please be careful. The engine speed will rise if a leak is present, showing the leak. Brake cleaner is also very flammable and toxic. Be sure to do this in a well ventilated area. A fire extinguisher might be a good choice too. You can never be TOO SAFE. I've been doing it for years without incident. If you need more clarification, leave a post... Hope this helps.
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Spray the intake manifold on cylinder number where it bolts to the head with intake cleaner and see if the rpm's change and the miss goes away temporarily.There was a problem at the factory with the intake gasket being creased on cylinder number 1. This issue tends to be a lean misfire issue.
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After my truck (2003 S10, 4.3) sits after running it for a bit, start it and it will start missing and the check engine light comes on. The miss will go away after about 5 minutes running and the light...

intake manifold gasket. when it leaks water will enter a cylinder causing the sprark plug to short out. when the engine gets hot enough the water will cook off in the cylinder allowing spark to take place. 80% chance intake manifold gasket, buy the upgraded part. 20% chance head gasket. Take the intake off and check for broken intake manifold gasket then buy parts.
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SOILED PLUGS

171 is a lean bank one check for vacuum leak at the intake manifold
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