Misfires and flashing CEL

[ecp]

Originally Posted by ike84

At tdc, both intake and exhaust valves should be closed. Hence, whatever pressure you put in should stay there. Even in a small space, 25psi is a lot of air. If you aren't getting it back there is a problem. You are effectively doing a poor man's leak down test, but I don't think you're gonna get any kind of good diagnostic data with the way you're doing it. You said the dealership did a leak down - what did it show?

The bottom line here is that if a cylinder won't pressurize, or won't hold pressure, you have a serious problem.

One caveat there - we have low pressure piston rings. So, in the absence of a crank case vacuum, expect some leak down. Not complete loss though.



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Poor mans leakdown yes. I have the cams out on bank one so all the valves are closed. The boxes of suspension parts sitting in my house drained me dry, and then this happened. I know it’s not the best or anywhere near precise, but it would give me a yes/no answer if wether there was pressure building or not.
I’m gonna give them a call tomorrow. They did perform a leak down and borescope but only mentioned the one valve that was open, which i was able to diagnose as the busted spring. I know the motor isn’t perfect. It sat for about two years and given the state it was in when i bought it, definitely neglected. that’s why i don’t want to put major money into a repair of a neglected engine with 124k miles. would rather put in a new or nice used one in the future.

I did have my buddy with a good borescope come by, we didn’t see anything. in cyl one it was hard to see with it being at tdc, but i didn’t want to rotate the engine with the cams out. But it’s not like we saw glitter or a big hole in the piston, just normal carbon buildup on it. Just wishing i put the compression tester on cyl one when i did cyl two....

[ike84]

Originally Posted by ecp

Poor mans leakdown yes. I have the cams out on bank one so all the valves are closed. The boxes of suspension parts sitting in my house drained me dry, and then this happened. I know it’s not the best or anywhere near precise, but it would give me a yes/no answer if wether there was pressure building or not.

I’m gonna give them a call tomorrow. They did perform a leak down and borescope but only mentioned the one valve that was open, which i was able to diagnose as the busted spring. I know the motor isn’t perfect. It sat for about two years and given the state it was in when i bought it, definitely neglected. that’s why i don’t want to put major money into a repair of a neglected engine with 124k miles. would rather put in a new or nice used one in the future.



I did have my buddy with a good borescope come by, we didn’t see anything. in cyl one it was hard to see with it being at tdc, but i didn’t want to rotate the engine with the cams out. But it’s not like we saw glitter or a big hole in the piston, just normal carbon buildup on it. Just wishing i put the compression tester on cyl one when i did cyl two....

Sorry dude, I'm not tryin to drag you down. I just don't want you doing all this only to find more issues after you put it back together.

At this point I think you're at the limit of what you can do from a diagnostics standpoint. I would call the dealer and ask them for the leak down numbers. If cylinder 1 had less than 10-15% loss of pressure, replace the springs and then put it all back together and see how she does. If they come back with some bull**************** though and say "oh we forgot to tell you that the compression on that one only held 15%" then you have a choice - put it back together and see what happens, hoping that there was a spring issue there as well that's now fixed, or drop the motor and dive into the block.

Unfortunately, with the piston at tdc, boreoscoping won't show you anything. Wall scoring happens at the bottom of the cylinder, and even it can be hard to see from the cylinder side with the piston in bdc because the piston covers it up. I remember reading that it's possible to scope it from the crank case side, but I don't know any details. Maybe someone can help out here.

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[ecp]

Originally Posted by ike84

Sorry dude, I'm not tryin to drag you down. I just don't want you doing all this only to find more issues after you put it back together.

At this point I think you're at the limit of what you can do from a diagnostics standpoint. I would call the dealer and ask them for the leak down numbers. If cylinder 1 had less than 10-15% loss of pressure, replace the springs and then put it all back together and see how she does. If they come back with some bull**************** though and say "oh we forgot to tell you that the compression on that one only held 15%" then you have a choice - put it back together and see what happens, hoping that there was a spring issue there as well that's now fixed, or drop the motor and dive into the block.

Unfortunately, with the piston at tdc, boreoscoping won't show you anything. Wall scoring happens at the bottom of the cylinder, and even it can be hard to see from the cylinder side with the piston in bdc because the piston covers it up. I remember reading that it's possible to scope it from the crank case side, but I don't know any details. Maybe someone can help out here.

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I gave them a call. went to voicemail and i haven’t heard back. i’m not too worried about bore scoring, i just want it to run, and then drive it till it eats itself one day. maybe it would take a month, maybe it would last a little longer, who knows. I might just bite the bullet and do the springs. I have all of next week off work, so plenty of time to re work things if the springs weren’t the solution.