Lt1 misfire big issue
Thread Starter
Racer
Joined: Oct 2010
Posts: 301
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Lt1 misfire big issue
i have ruled out any and all ignition components. a little while ago it started making a clunking noise but sometimes sounds like a back fire so i ran compression tests and cylinder 1 seems to be low
heres what i thought; could be possible broken rocker, valve spring shot or valve seal (on exhaust valve), timing or piston rings
i pulled off the drivers side valve cover and the rockers appear to be fine no stripped holding bolts nothing i cranked it over a few times and everything seemed to move appropriately what should i look for if its a spring or valve seal? PLEASE say its not piston rings....
ahhhhhh HELP lol i cant figure this out with out extensive removal of parts.
heres what i thought; could be possible broken rocker, valve spring shot or valve seal (on exhaust valve), timing or piston rings
i pulled off the drivers side valve cover and the rockers appear to be fine no stripped holding bolts nothing i cranked it over a few times and everything seemed to move appropriately what should i look for if its a spring or valve seal? PLEASE say its not piston rings....
ahhhhhh HELP lol i cant figure this out with out extensive removal of parts.
Last edited by CAmaninacan; Oct 24, 2011 at 06:20 PM.
Intermediate
Joined: Sep 2006
Posts: 38
Likes: 1
Broken valve springs can be spotted by close inspection of the spring coils. A small mirror and a good light source will help. Sometimes you can use a vacuum gauge to detect a broken spring which will cause the reading to jump around regularly. It helps if you know before hand what a good reading looks like.
Bad valve seals do not directly cause misfires. They allow oil to enter the intake or exhaust tracts which can show up as blue smoke out the exhaust. On the intake side they will eventually foul the spark plug and cause a misfire.
Valve seats or the valves themselves (not mentioned) can become damaged or worn and cause a loss of compression and misfire. The best way to detect this is with a leak down test.
If you redo a normal compression test after a few small shots of oil (wd 40 etc.) have been put into the spark hole you may see the reading go up temporarily. This is indicative of a ring or other cylinder related issue (the oil helps seal the chamber).
Bad valve seals do not directly cause misfires. They allow oil to enter the intake or exhaust tracts which can show up as blue smoke out the exhaust. On the intake side they will eventually foul the spark plug and cause a misfire.
Valve seats or the valves themselves (not mentioned) can become damaged or worn and cause a loss of compression and misfire. The best way to detect this is with a leak down test.
If you redo a normal compression test after a few small shots of oil (wd 40 etc.) have been put into the spark hole you may see the reading go up temporarily. This is indicative of a ring or other cylinder related issue (the oil helps seal the chamber).
