p0300 issues from hell

ok heres my problem My 2001 silverado started out life as 6 banger but now has been converted to a 5.3L. The truck keeps giving me a code for random missfire when on the highway or wot, when i check to see what cylinders it is it shows 100s of misses on each cyclinder. The thing is my 6 banger kept giving me this code before i replaced it with the 5.3l. Im lost at where to go Ive changed the fuel pump, o2s, stock mass airflow to a grantelli mfs and high flow cats. Both motors had headers, cold air intake, free flow exhaust and nelson tuned computers. ANy help or ideas would be great. Thanks

A code P0300 may mean that one or more of the following has happened:

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer
Possible Solutions
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

can you feel the misfires during a brake stall or 4th gear, tcc lockup, accelerating?

did u put the stock metal boot covers on the plug wires? take em off. they may be arcing out

I did not use the stock boot covers because they didnt fit on the new msd wires. The plugs are E3 brand new. it only seems to do it during hard acceleration or cruzin on the highway the truck will go into a shutter and then ses light flashes and shows a code of p0300, i never have a problem with it while in town. Whats driving me insane is the fact that i had this exact problem with the 6 cyclinder motor so i upgrade the truck to a 42000 mile 5.3l and this problem is still present im lost on what to do. AS for feeling a mis during brake stall, 4 gear, tcc lockup Im not sure what these are and what to be looking for. Im greatful for the help! Thanks

Did you use the junk E3 plugs in the 4.3 too?

the truck has brand new plugs, wire, magnaflow cats, cold air intake, new o2 sensors, new masair flow sensor, new headers, new fuel pump, new injectors (because the originals had varnished closed from the old fuel while sitting in the junkyard), new pressure regulator. Whats wierd is that it doesnt always do it It some how can happen and then go away in the same drive cycle. AHHH!

no the 4.3 had accel and ac delco before I gave up and went to the v8. Are the e3s bad plugs?

E3's crappy plug. Stick with Iridiums. Either AC Delco or NGK's.

Ngk tr55

Quote:

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Originally Posted by RUFFNECK

E3's crappy plug. Stick with Iridiums. Either AC Delco or NGK's.

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ya im running the e3's right now idk if there crap or what should i switch em as well???? or would it make any diff?

I had them in my 99 tahoe and they made it run bad. Loss of power, some random misfire, poor gas mileage.

Quote:

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Originally Posted by RUFFNECK

I had them in my 99 tahoe and they made it run bad. Loss of power, some random misfire, poor gas mileage.

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ill see if vatozone has some if not ill order some tomorrow....

i had e3's in my SS ran fine.. no issues at all.. good MPG
put in bosche platinum ...ran the same
i have ac delcos in there now.. runs fine..
i , personally, have not noticed a difference in any of these plugs.

Before you do the shotgun approach and replace a lot of parts, get a scanner on the truck and see which cylinders are misfiring.
It's very easy (if you have access to a scanner, or hptuners), simply pull up all the 8 cylinders and watch for misfires.
It's gonna show you which one is missing.

I have looked at my truck with a snap on scanner and it shows that all cycliders have missfires they ranged from 50 to like 300 betwwen all eight cylinders. Im guessing Ive got something that both the v6 and the v8 use on the truck thats causing this since the the miss and the code happen at the same times with both engines. What it could be i have no clue! plulledplugs and they looked fine, may have to take it to dealer.

does any of the harness from the old v6 exist on the v8?

No i replaced the entire engine harness with the factory v8 harness. However today I had an 02 sensor throw a p0160 and when i started looking for the problem i found a broke through wire and another pulled wire in the same section of harness down to the passanger rear 02 sensor. So i cut out the bad section of wire and fixed the broke wire to new condition. Took the truck out tonight and ran it had no problems with a missfire. So i dont know how that was causeing the problem but as of right now it appears that big blue will be back in action ready to show tuners what a real motor is while turning 33x12.50 mudders and 6inches of lift!