Thread: Number 3 misfire

i would put this in the same thread but i couldnt find it. but my 2001 pontiac grand prix gtp stock, it started a long time ago i went though the whole ignition system all good check compression good, it does it once and a great while right about oil change time i change oil and put a quart of mystery oil in and it goes away and runs smooth, could it be a sticking valve anyone have any ideas the dealers around here said i have to get the valves done anyone had this problem and if i gotta take the head off how hard is it to do??

i got a crankshaft postion sensor going too would that affect the number 3 cylinder

it quits after i change the oil and put mystery oiil in

but goes real good for while till about when i gotta do another oil change

how do you resolve that?

try a half can of seafoam in the crankcase about 500 miles before you change ur oil next could dislodge some gunk stopping up a lifter...

i usally use a can in the intake also sorry i should of said that also

thats good for cleaning the intake an valves etc... but just doing that doesnt get seafoam to the lifters to clean them hence putting it in ur crankcase aka where the oil goes

so just put half a can in when i change my oil?

Originally Posted by slick2500

If you have a bad crank sensor yes it can cause misfires, a new one is cheep but one.

This*


I had the same problem bad sensor replaced and no problems since

Sent from my SGH-T989 using Tapatalk 2

500 miles before not a garunteed fix but could help... try this^^ too

there really isnt a check... you could take the valve covers off run the engine for a few seconds while watching the rockers to see if #3 isnt moving like the rest but that has the potential to be messy... just run the seafoam and if that doesnt work your only out $9 max, try the crank sensor... but im gonna lean more towards sticky lifter if it only shows up around oil changes...

i need to change the sensor bc its been acting up tach dropping to zero and stalling

that little bit of info could have helped our diagnosis 100 fold... unless it just started to happen