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98 5.7 Vortec Code P0300 Random Misfire

98 5.7 Vortec Code P0300 Random Misfire

Postby 98Vortec1500 [OP] » Jan 02 2013, 3:16am

I have a 1998 Chevy 1500 Vortec 5.7 V8 2WD. I have a Code P0300 which is a Random Misfire Code. The engine idles very rough and you can definitely tell it's a misfire from the exhaust end. From what I've been told is that these engines are notorious for having intake manifold leaks so I went ahead and changed out the intake manifold gaskets and headgaskets since it's been a very long time. I took my heads to a local machine shop to have them inspected and resurfaced and turned out both heads were cracked. So I purchased brand new heads from JEGS along with ARP headbolts. I've also replaced the Mass Air Flow Sensor, EGR Valve, Exhaust Manifold Gaskets, Spark Plugs, Spark Plug Wires, Cap, and Rotor. I didn't know how to test the Spider Injection and it "looked" fine so I put it back how it was. I installed the Distributor with No.1 Cylinder at TDC so I assume that would be 0 Degree Initial Timing. I lined the rotor terminal with the Cylinder No.1 Runner on the Distributor Cap. Went to start up the car and I noticed the idle was around 800RPM on a cold start and it just stayed there after warming up. The Code is still present and came back after I erased it. Unfortunately the misfiring didn't go away and there was a noticeable power loss worst than before I'm running out of ideas and don't have great knowledge in these cars and engines. I'd appreciate any help, advice, or suggestions. Thank You

Questions:
Would over tightening the lifter cause anything? My Adjustment Procedure: 0 Lash/ Half Turn Preload or 180 Degrees on Base Lobe
How would I go about setting the timing on the 98 Vortec?
How do I test the Injectors?
How do I check the Coil?

Current Issues:
Code P0300
Misfiring/Rough Idle
Low Idle on Cold Start-Up
Power Loss
Water dripping from the tailpipe------Head Torque Procedure: 70ft lbs in 3 steps according ARP's Instructions
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98Vortec1500
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Year: 1998
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Related Topics  P0300 Random Misfire Occuring Randomly   random misfire   4.8 random misfire, very weird idle   2005 silverado misfire, p0131 , p0300 , p0171 help please   random misfire........2003 gmc 1500hd   2004 Silverado 1500 5.3 Random Misfire HELP!!!!   Multiple random misfires on 1998 vortec   P0300 code   Poor running, bad mileage and now a random misfire, too!   Clogged Cat or Bad 02 Sensor? Random Misfire...   random multiple misfire soo bad you can feel it   P0405 + P0300 code - looking for ideas   03 Silverado 5.3 dreaded p0300 code   Injector pigtails...Misfire code. 
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Re: 98 5.7 Vortec Code P0300 Random Misfire

Postby ASTE25 » Jan 02 2013, 7:33am

Overtightening a lifter could cause a misfire, but it should show up on a particular cylinder, not as a random misfire. I assume you replaced all the ignition parts with new (plugs, wires, cap and rotor). If you got the distributor reinstalled in the wrong place it will cause problems. Inside the distributor is the camshaft position sensor. If it is not in the EXACT location it should be, it will cause problems. You will have to have a diagnostic scanner (not a code reader) to get it set back in it's correct location.
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Re: 98 5.7 Vortec Code P0300 Random Misfire

Postby racinnick1 » Feb 03 2013, 9:07pm

ive got a 1999 chevy k1500. im havin the same problem with the misfire at low rpm speeds. ive done put new plugs and wires, new egr valve, coolant sensor, cap and rotor button, new injectors, and head and intake gasket. Those anyone have a way of fixin this????
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Re: 98 5.7 Vortec Code P0300 Random Misfire

Postby ASTE25 » Feb 03 2013, 9:28pm

I would suggest having someone with a diagnostic scanner checking to make sure the camshaft position sensor is in the coreect location. I would also have them perform a crankshaft sensor relearn while they were at it.
Jordan
2013 Blue Granite Metalic Silverado 2500HD Z71 4X4 extended cab regular bed
6.6L Duramax/Allison 6 speed
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Re: 98 5.7 Vortec Code P0300 Random Misfire

Postby chevyman 007 » Oct 10 2013, 12:09am

Hello I just had the dreaded P0300 code and I had put in a new distributor with a fixed plate. Come to find out that the plate was the problem. When you put in the distributor has inside of it a 6 and an 8. you lock down the distributor pointed at the 8 at top dead center #1 on a v8 to set the timing. Also a lot of the distributor gears are getting worn so they are causing a P0300 code. the 6 is for a V6. I know one more thing to look for. sorry don't know how to post pictures but it can be a big problem.
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