ok so iv posted recently about my issues with my truck and its missfiring. today i had it sent back into the smog class at school and for the second time in two days it passes smog for the gasses but fails for the mil being on because of the random missfire. so they did the tsb for the plug wires and then checked for the miss again and it was still there they then performed a compression test. compression should be 125-135 each cylinder(correct me if im wrong) and cylinders 346 were all low 6 being the worst at 105 and 3 and 4 around 110-115. they are also the cylinders that show up as my random missfire everytime we clear the codes.

so horrible news to me tonight we put some seafoam in the brake booster vacuume line and tried to see if maybe i had some sticking valves or lifters and still have the miss and doesnt seem to have helped beyond cleaning the heads. tomorrow i plan on performing a cylinder leak down test to determine if its rings or heads.

i called tonight and found i can get both heads for 700 or a long block for 1700. i almost am leaning towards the long block but dint know what would you do? even if its only the heads would you replace the block nyways?

 

Those numbers don't indicate a compression test failure.

 

im pretty sure you cant have more than 15% difference 105 is a fail maybe my math is wrong (im tired and pretty pissed about the truck) but i believe 15% of say 125 would be around 18-19 and 105 would fail the other two your right probably wouldnt be a fail but when the other 5 are all right about 125-130 from what they said. its a fail in my book its clearly low enough to be causing a missfire that nothing seems to be fixing.

 

His spread is 105 to 115, which is within tolerance -- your low cylinders are not quite 10% below your high cylinders. On one of these engines with typical mileage, 105 is just fine.

 

Are you having any other issues? Could it be a blown head gasket?

 

or a cracked head....

 

Or a weak coil? The engine just doesn't like the spark plugs? (what plugs do you have in their?)

 

With 105PSI low and 115PSI high? Possible but not anywhere near likely.

 

ok so after lookin at my post again i think maybe i wasnt too clear so ill try again cylinders 1, 2, 5, 7, 8 are all showin in the 125-135 psi range. cyliner 6 is at 105 psi and 3 and 4 are in the 110-115psi range that shows a compression leak correct? as for the spark plugs i cant remember what i put in there what ever oriellys carried. and then im not sure about the head gaskets yet i was tryin to get in the shop today to do a cylinder leak down test but was unable too. im really hoping its a head gasket but i still fear the worst. cracked head another possibility but i still wont knwo until i do the test so im kinda stuck waiting till then its real wierd you can feel the miss fire on idle but when you hit the gas it feels fine. sucks gas like crazy but drives like there is nothing wrong.

 

If you used Bosch plugs, they've been known to cause misfires, for example. The plugs do really matter, you should probably pull one and see which you purchased.