Multiple/Random Misfire

I have a 1999 Chevrolet Malibu with the 3100 V6 in it and it giving me a super bad miss and is giving the PO300 code.

I once had a bad overheating problem. It turned out to be the head gasket and warped heads. I had the heads milled and checked out to see if there was any life left in them. I was told that both heads was warped. All the valve and springs was in good shape and working just fine with no sticking at all.

So... I replaced all the gaskets from the top of the block upwards. When i say all... I mean everything that came with the complete gasket kit. I had the seals and valve guides replaced after the heads was milled, so i would be sure that the heads was good.

After putting everything back together making sure to use new bolts on everything with all the proper and new torque settings... The car will start just fine, but, will run and sound like an old washing machine. I made sure that all the pushrods was in the proper location when i put the engine back together. But, like i said. The engine has a terrible miss to it. So i checked the codes using my code reader and get the dredded PO300 code. Which is the Multiple/Random Misfire. heck i knew that even without reading the codes from the computer. It is the only code i get.

I went back through the whole engine and made sure that all was well and had no leaks or air sucking anywhere. I used a .003 filler gage to be sure that the gaskets was properly seated. Everything check out well there as well. I made sure there was no air in the fuel line by purging the bleeder on it. All my wire connections are in their proper places and connected well.

I have replaced all of the plugs and plug wires with the original brands. I made sure my plugs was properly gapped and seated well in the heads. I have checked and made sure that i had spark from each and every plug and plug wire. All is good there. I have checked out the coil packs as well and everything is good there.

I also have checked out the fuel rails and injectors too. They are all doing what they are suppossed to do. With no leaks. All are firing like they need to.

The only thing i haven't done is put a timing light on it and see what it has to say. I am thinking that for some odd reason that the timing may be 1 or 2 teeth off. I may just even pull th timing chain cover and re-time it, so i can be sure that is correct.

I have done everyhting that i can possibly think of.

I am asking the good people here if i may have overlooked anything or i have done something wrong or that it may just be the timing.

Any help at all will be greatly appreciated.

adrenalin

1) Check PCV hoses.
2) Are you sure the rockers are fully seated?

Usually this means bad plugs or poorly seating rockers.

1) Check PCV hoses.
2) Are you sure the rockers are fully seated?

Usually this means bad plugs or poorly seating rockers.

The plugs and wires are all brand new and getting fire. I will be sure to check them out again and double check the gap too.

I can here a popping sound at the PCV Valve where it connects into the right side valve cover (like it is making an up and down movement). The boot is busted and was tape by the previuos owner. I am going to replace that boot and check out the rocker arms again ( i've checked out the right hand side and double checked the placement of the push rods and they was all good). I do need to check the left hand side and I will let you know how it all turns out.

Thanks for the reply.

adrenalin

My car was popping and running ragged because the PCV sleeve was cracked and the PCV was full of gunk. I replaced it and fixed the sleeve and it ran mucg better.

I have absolutely had it with this car.

I just finished checking the timing to be sure the engine was in time. After pulling the timing chain cover and checking everything, the timing is just fine.

I checked my PCV hose and replaced the boot and the PCV valve both just to be sure. The popping from the PCV valve has stopped. But my problem still exist. It is like the thing is only running on 4 of the 6 cylinders. I physically toughed each terminal coming from the coil and got a jolt each time. So i know the coil is good.

I have checked out to verify that i didn't have any gap around the heads. I cannot even get a .001 feeler gauge in there. So i know i have no gaps or leaks from there. I have checked the intake gasket where i could reach and everything is fine there. I have checked the upper intake gasket and all is well there too.

I do not know what else i can do, except pay a mechanic a lot of money i do not have.

I consider myself and above average mechanic with a lot of years experience. None professional though. I have brought a bunch of cars back from the dead.

But, i think i have gotten my butt kicked on this one. I have absoultely ran out of ideas except junking the car or swapping engines. But, the swapping engines thing will cost me a good bit of money. Money that i do not have. I am a disabled American Vet and on get paid once a month.

So....

If anyone has any ideas, thoughts and or suggestions. please feel free to let them loose.

Thanks for hearing my crying on this one.

adrenalin

Heh, Heh, Heh. Again, I ask - did you check the rockers to see if they are seated properly? That may be your problem. It is mine. Car runs fine, but I had to do a heli-coil on the rocker bolt holes. Now I need to change that head. Again, check it out.