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Help PO300 misfire code

 
bada
I love my Chevy Chevette!
Posts: 1
Joined: 05/08
Posted: 05/11/08 06:08 AM

I recently put a ZO6 LS7 in my 1932 pro street truck. I got it from a wrecked donor car. I sent the PCM to speartech to rework it. I am running a turbo 400 tranny. The problem I am have is, it Keeps giving me a PO300 misfire code. Its not missing, and runs great. Can I send my PCM back to speartech and get the misfire code totally removed? If so will that cause any problems? I would also like to make the knock sensors a little less sensitive. Thats only because the truck has tons of shake rattle, and roll noise. Being that old. ANY help would be great Guys.  

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waynep712
I love my Chevy Chevette!
Posts: 11
Joined: 06/08
Posted: 06/03/08 04:42 PM

i know that this is an old post....    when you installed the wiring harness... did you  install the obdII data link.?????     do you have a scan tool?????

it does not take very much of a miss to set a po300... misfire... only one misfire in 10 minutes .....    several times...

does that have individual coil?????     can you do output tests on them with a coil tester????/   ajustable screw in plastic with a gator clip on one end and the spark plug wire on the other...  this will test the max output of each coil.... they do breakdown internally causing intermitant misfires...

sometimes the spark plug boots will leak voltage to the exhaust manifolds or the head...

the output power needed to fire the plugs is higher under load than at idle...

you really need to look at the misfire code in the ecm... there will be data saved with it... that shows all the sensor readings at that instant when the code was set...   that saves a lot of time.... as then you can duplicate the speed and load  to watch the  scan tool readouts...

po300s are mechanics nightmares...   so many small intermitant things to make them go wrong....  

i worked in a shop.... the owner wanted to fix this camaro... 96 or 97... misfire..

i told them as i walked by to swap the coil first...    they did the cap and rotor, wires, plugs... it was still there...  it took them hours...pulling the water pump to get to the optispark cap... they cussed and groaned... changing the wires and plugs...  even on a lift...     then it still misfired..400 bucks plus in parts.     i put on a 21 buck coil and it fixed it...////      good luck....


oh....     and you have to use silicone dielectric grease on both boots of each wire... only in the boots....  use a q tip... a screwdriver tip... what ever ... just so it does not get on the contacts... only the insulator.....   failure to use dielectric.. (clear) compound will allow high voltage leaks past the boot....

the quad 4 coil packs  if you do not use it... will burn out in a few thousand miles....      just think about it... they have been using it to insulate high voltage for decades....  the red wire to the top of the back of your tv tube has silicone insulatiing grease on it....  this again prevents spark leakage...

little packages of it are next to the cash register at most parts stores... 99 cents...

nobody who knows what they are doing builds motors without sealant...

plumbers use sealant...

try it.... you are only out a buck or two.....




and for all those guys... who have a tube of dielectric tune up grease...    PLEASE do not use it on brake caliper slides... or bolts....  it is totally the wrong stuff..

it will lock up the caliper slides so tight that you cannot even move them with a 30 ton press...  i've tried..      brake moving parts lube is SILGLIDE...  or white lithium grease.. thank you in advance...  

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