how does "bad valve's" cause a misfire?

[joe sobo]

i have read that "bad valves" will cause a misfire code. i have put new plugs, wires, swapped injectors, to no avail.
i am trying to understand if someone could shine some light on this situation for me. i bought the car with a jumped timing belt. it bent two valves in #4 cylinder and two valves in #1 cylinder. i replaced them and re-seated them.
i want to know what/how exactly does a bad valve trip a misfire code. i have read most of the threads on it, but do not define what the exact problem MAY be.
please, if someone with "experience" with headwork/funtion,please chime in
also what leads me to beleive that it may be something with the head, is that when it starts to misfire, i will turn the key off, and then restart the car and it will be fine for some time. other times i drive the car, it does not come on at all.....wtf? if i had bad valves, would they be bad in the cylinder that is getting the misfire?

 

[JusMX141]

2G misfire codes are a pain in the ass. After we installed Brian Crower 272's in my buddy's 2G, he constantly got random misfire codes (I'm guessing due to the excessive overlap) until he bought DSMLink.

If the valves aren't sealing combustion gases in the cylinders, obviously it will cause a misfire because of poor combustion. Of course you'll have low compression in that cylinder as well.

Why didn't you re-lap all of the valves while the head was off? Anything can compromise seal- leaking valve seals, pitted valves / valve seats, etc.

 

[Clutch GSX]

i have read that "bad valves" will cause a misfire code. i have put new plugs, wires, swapped injectors, to no avail.
i am trying to understand if someone could shine some light on this situation for me. i bought the car with a jumped timing belt. it bent two valves in #4 cylinder and two valves in #1 cylinder. i replaced them and re-seated them.
i want to know what/how exactly does a bad valve trip a misfire code. i have read most of the threads on it, but do not define what the exact problem MAY be.
please, if someone with "experience" with headwork/funtion,please chime in
also what leads me to beleive that it may be something with the head, is that when it starts to misfire, i will turn the key off, and then restart the car and it will be fine for some time. other times i drive the car, it does not come on at all.....wtf? if i had bad valves, would they be bad in the cylinder that is getting the misfire?

Did you replace your guides when you replaced the valves? If not, then they are probably not sitting right since the guides were warped when the valves were bent. Did you check for damaged valve seats? How did your chambers look? Have you done a compression test or a leak down test?

 

[joe sobo]

well, i think i will be picking up a compression tester todat. thanks guys'

 

[TastyTalon]

DSM heads can be very touchy. In my experience, when you pull a head and fix something small like that, you should always go through and replace valve guides and all that crap because little problems always turn up. Also if you don't have a tuning program it could be something random triggering that is not really a problem at all.

 

[Boma]

2G misfire codes are a pain in the ass. After we installed Brian Crower 272's in my buddy's 2G, he constantly got random misfire codes (I'm guessing due to the excessive overlap) until he bought DSMLink.

If the valves aren't sealing combustion gases in the cylinders, obviously it will cause a misfire because of poor combustion. Of course you'll have low compression in that cylinder as well.

Why didn't you re-lap all of the valves while the head was off? Anything can compromise seal- leaking valve seals, pitted valves / valve seats, etc.

I've read somewhere that if you install cams on a 2G that you'd have to modify the CAS (which for some reason, 1G owners don't have that much problem), although I'm also quite aware that its a pain so some people just go the DSMlink route. I do like the sound of 272's idling rumble. Heh.

 

[joe sobo]

well, i would hate to hook up dsmlink, to find out that there is a real problem there. instead of just hiding it

 

[rhodess89]

should have lap the valves back in and had the carbon removed from the head as that can raise compressions and a knock is thus created.