98z71 5.7 multiple misfire P0300 fouling 1 3 5 7 plugs with gas what causes ths

Asked by Jan 05, 2016 at 12:59 PM about the 1998 Chevrolet C/K 1500 Cheyenne RWD

Question type: Maintenance & Repair

11 Answers

29,065

only on that side... try and go up 2 heat ranges on that side,,,and / or first .. take some good pictures of those plugs and post them...

79,015

Possible causes po300:... - Faulty spark plug (s) - Faulty ignition coil (s) - Clogged or faulty fuel injector (s) - Intake air leak - Fuel injectors harness is open or shorted - Fuel Injectors circuit poor electrical connection - Ignition coils harness is open or shorted - Ignition coils circuit poor electrical connection - Insufficient cylinders compression - Incorrect fuel pressure Tech notes The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem,

1 of 1 people found this helpful.

Replace plugs wires dis cap n rotor button still doing same thing

79,015

Check for vacuum leaks, that is a Vortec engine, intakes are prone to leak, check the bolts, there are only 8 of them, torque to 15 to 20 ft.lbs. They say 12 ft.lbs. but that is pretty light.

1 of 1 people found this helpful.

Check all that n leaks on intake

79,015

By chance did you use carburetor cleaner? If there is a vacuum leak spraying the carb cleaner would make the rpm rise. If still all good then you are going to have to dig into it to find the problem. How many miles on her? Compression test may be in order. After that or you could do first is get the coils checked. I would check the electrical connections to the injectors also.

Compression is good has little over 100000 on it have checked ll connection s injection all good fuel pressure is correct

Only has the one coil pack could it cause it to misfire n foul plugs on one side

79,015

Well yes, that can be tested, I believe Auto Zone can. But I know I have looked on line on how to and what specs to look for when testing a coil, but you would need a volt ohm meter.

I have a 96 chevy silverado z71 4x4 extended cab only has 97,000miles.. motor 5.7 ...service light starts to flash for about 20 seconds then stays on comes up as a #5 misfire ive changed plugs and wires but it didn't fix still comes up #5 misfire

Change cap rotor oil oil filter check all vacuums replace fuel pump still missing misfiring number 5

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