P300, P301, P303, P306 Codes.. Random misfires

12,185

Asked by Dec 14, 2014 at 03:59 PM about the 1999 Chevrolet Blazer LS 4-Door 4WD

Question type: Maintenance & Repair

Any input would be appreciated. 4.3L 168,000mi. Scanner is pulling up the infamous P300 code. Just within the past few days CEL is blinking, lack of power. Ignition is good providing good spark. Compression test was in the range of 130 -140 on 1-6 cylinders so I know the valve seats are good. I also ran the truck without the O2 sensor installed to see if I had a back pressure problem, but didn't make any difference.

I do not have a fuel pressure gauge to test fuel pressure, but I'm leaning towards a fuel delivery problem. I'm thinking that I'm having a problem with the fuel spider assembly and\or fuel regulator. At this mileage I would like to replace the entire assembly. At around $300, I would like to think that this is the problem as I've seen a lot of these as the problem on other message boards.

Any insight before I take the plunge and dump the money into this 14 year old truck? Is there anything else that I might look at that I'm not thinking of.

Thanks.

6 Answers

70,305

You may have it figured out mark,the only other thing would be ,crank sensor,or distributor.

1 of 1 people found this helpful.

This could be caused by a bad dist. cap and/or wires or spark plugs.I change plugs when this happens because it's the cheapest solution.If the plugs show spark they can still be bad.Then I test the wires to ground and if there's spark,my next step is to remove the upper intake.Leave spider injector hooked up.Disconnect all electrical supply to the distributor, and coil wire too, and pull all poppet nozzles from heads.Put paint can caps under all six poppet nozzle injectors.You can have someone turn vehicle over and watch for fuel to fill caps.It will show immediately if injectors are filing with fuel. My guess is it's the injectors.A pressure regulator is a long shot. If you have a manual shift veh. make sure it's in neutral and parking brake is on.I have purchased injector sets from ebay and rebuilt with known working injectors to replace bad ones.

1 of 1 people found this helpful.

A fuel pressure gauge does help to determine fuel pressure after pressurized and when key is off. For 60 bucks, It is a good investment.I.M.O. Good luck.

5,755

Harbor Freight has a fuel pressure tester on sale right now for $20.00. Go to: http://www.harborfreight.com/automotive-motorcycle/diagnostics/fuel- injection-pump-tester-92699.html

1 of 1 people found this helpful.
12,185

Thanks guys, I appreciate the input. I'm moving forward with the project this week. Hope this works..

12,185

Good news! I replaced the fuel spider with the newer designed injectors and the truck runs great! no misfires. Cleared the codes and nothing came back. Only other things I replaced were a new PCV valve and gaskets. Runs like new! Fantastic!

Your Answer

Blazer

Looking for a Used Blazer in your area?

CarGurus has 931 nationwide Blazer listings starting at $950.

ZIP:

Chevrolet Blazer Experts

  • #1
    Andrew Olsen
    Reputation
    2,120
  • #2
    yetilikesbeer
    Reputation
    1,410
  • #3
    Rowefast
    Reputation
    1,080
View All

Related Models For Sale

Used Chevrolet Tahoe
793 Great Deals out of 41,831 listings starting at $1,987
Used Chevrolet S-10
12 Great Deals out of 1,207 listings starting at $1,600
Used GMC Jimmy
202 listings starting at $2,500
Used Chevrolet Silverado 1500
2,660 Great Deals out of 174,213 listings starting at $955
Used Ford Explorer
1,223 Great Deals out of 69,685 listings starting at $1,000
Used Jeep Grand Cherokee
1,041 Great Deals out of 72,264 listings starting at $1,195
Used Chevrolet Camaro
442 Great Deals out of 31,709 listings starting at $1,450
Used Chevrolet C/K 1500
820 listings starting at $2,436
Used Ford F-150
3,218 Great Deals out of 223,765 listings starting at $1,200
Used Chevrolet Suburban
486 Great Deals out of 24,182 listings starting at $1,799
Used GMC Yukon
593 Great Deals out of 20,332 listings starting at $2,500
Used Toyota 4Runner
334 Great Deals out of 26,862 listings starting at $1,800

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.