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1999 Chevrolet Suburban cylinder 3 misfiring?

I bought a 1999 Chevrolet Suburban approximately 2 months ago. Since then we had noticed it dragged when accelerating and didn't shift smoothly. Took it to the shop where they said it needed a major tune up, costing $850. A couple of weeks later I started the vehicle and it died, electronically speaking, everything went dead. They found that the battery cables were actually burned, replacing them cost $400. Now the service engine light is coming on. I took it to Checker Auto and had them run the diagnostic on it. Code came back as P0303, the guy who checked it said that means that cylinder 3 is misfiring. What could be the cause of this and how do I check it to find out what it would be?

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P0300 is a multiple cylinder misfire and is used by all OBD2 vehicles on the road in the USA that is 1996 and newer, P0301 is cylinder number 1..P0302 is # 2 and so on...that tune up may have been needed and parts and labor are have a cylinder that is misfiring and the cause must be located..possible causes are intake manifold air leaks..secondary ignition problems..fuel injectors..plugged EGR system if it has one..failed head gasket..burned or cracked valves..I have seen some crazy need a tech on that one not a mechanic.

Posted on Sep 10, 2009

  • 1974SD Sep 10, 2009

    I was thinking of 2004 ish type engine in your suburban not a 1999 model with the 350cid..different animal alltogether..that changes everything..I would leakdown test on that cylinder first to see if it is not a mechanical problem..if ALL of the ignition parts were changed then most likely cause would be a stuck injector tip on that cylinder..there is a GM TSB on this problem and I have had some luck with a fuel system cleaning with strong store bottle cleaner will work..if that will not work you can remove upper intake and replace that injector..or move it to another cylinder to verify the problem. years ago were not sold individually had to buy whole unit like 900. have that shop print out the TSB so you can read though it some cases gm replaced whole system with new design..maybe still covered in CA.. good luck.


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A DTC code P0303 applies to a 6.5L diesel engine.A proper misfire code for gas engine will be a P0300.
I think you need to return to the shop that did the work for you. Most places give a 12 month, 12,000 mile warranty.
This is how my GM diagnostic chart reads when I look up a P0303 DTC.
Engine Controls - 6.5L

  1. Diagnostic Trouble Code (DTC) List
  2. DTC P0303 Cylinder 3 Misfire Detected

Posted on Sep 07, 2009


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