Misfires and flashing CEL

[ecp]

Originally Posted by ike84

Not to derail this victory (good job finding the broken spring!) But what is going on with cylinder 1? There's no "limp mode" that will cause total loss of compression.

You said the dealer did a leak down test - what did they find on cylinder 1?

If you have no compression in cylinder 1 and a leak down supports that finding, I think you still have more trouble ahead.

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I’ll have to ask them. all they mentioned was a valve was stuck open. I had assumed it had no compression like cylinder 2 because it was also not firing, but i never checked with the gauge. so if there’s nothing wrong that i can see right now, i was just wondering if it could just be the ecu not keeping up due to the dead cylinder and not a mechanical problem

[ecp]

I did my own sort of test. i modified my compression test hose so it can put air into the cylinders, and then when i unplugged the compressor line, i’d feel for air coming back out of the hose that’s screwed into the head. cylinders two and three had good pressure when i undid the line, but cylinder one had nothing. keep in mind all valves are closed, but cylinder one is at TDC.

My question is:
Is the reason that i felt no air coming back out of cylinder one because there’s no space for it to go (TDC, very small space vs the other two pistons which are further inward etc)
or because there’s also a problem with cylinder one and the broken valve spring on cyl two isn’t all that went wrong.
Cylinder one was not firing, i’d like to think it’s just the ecu not being able to compensate for cylinder two which had zero compression, but this is having me re think my approach. I don’t want to pull the head, but if i have to, i have to.

i only put in about 25 psi. Should i try closer to 100 like what people do when they perform leakdown tests?

[ike84]

Originally Posted by ecp

I did my own sort of test. i modified my compression test hose so it can put air into the cylinders, and then when i unplugged the compressor line, i’d feel for air coming back out of the hose that’s screwed into the head. cylinders two and three had good pressure when i undid the line, but cylinder one had nothing. keep in mind all valves are closed, but cylinder one is at TDC.



My question is:

Is the reason that i felt no air coming back out of cylinder one because there’s no space for it to go (TDC, very small space vs the other two pistons which are further inward etc)

or because there’s also a problem with cylinder one and the broken valve spring on cyl two isn’t all that went wrong.

Cylinder one was not firing, i’d like to think it’s just the ecu not being able to compensate for cylinder two which had zero compression, but this is having me re think my approach. I don’t want to pull the head, but if i have to, i have to.



i only put in about 25 psi. Should i try closer to 100 like what people do when they perform leakdown tests?

So you pressurized the cylinders (with the head cover off I'm assuming?) And cyls 2-3 returned pressure when the supply line was vented but cyl 1 returned nothing?

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[ecp]

Originally Posted by ike84

So you pressurized the cylinders (with the head cover off I'm assuming?) And cyls 2-3 returned pressure when the supply line was vented but cyl 1 returned nothing?

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yup i have the head cover off, and removed the broken spring. was just trying to get my parts list together and wanted to make sure i didn’t need to add a bunch of things to it. Cyl one returned very little after doing the test again with more pressure put into it. I think it’s due to the fact that there’s a much smaller space for air to go since the piston is at tdc. starting at zero and firing up the compressor it builds pressure nearly as quickly as when an air tool is attached to the line.
there’s a slight hiss coming from back near the crankshaft area which i assume is just air seeping past the rings. it did it on all cylinders

after putting more pressure in and confirming air returned on cylinder one numerous times i think it’s worth a shot putting new springs in and trying to fire it up, and maybe it was just an ecu error causing cylinder one to not fire. I could be wrong, but i could be right. Only one way to find out.

The fact that the dealership only mentioned a valve being stuck open on one cylinder also leaves me to believe that they didn’t really find any other issues, but i’m gonna give them a call tomorrow and ask just to double check.

[ike84]

Originally Posted by ecp

yup i have the head cover off, and removed the broken spring. was just trying to get my parts list together and wanted to make sure i didn’t need to add a bunch of things to it. Cyl one returned very little after doing the test again with more pressure put into it. I think it’s due to the fact that there’s a much smaller space for air to go since the piston is at tdc. starting at zero and firing up the compressor it builds pressure nearly as quickly as when an air tool is attached to the line.

there’s a slight hiss coming from back near the crankshaft area which i assume is just air seeping past the rings. it did it on all cylinders



after putting more pressure in and confirming air returned on cylinder one numerous times i think it’s worth a shot putting new springs in and trying to fire it up, and maybe it was just an ecu error causing cylinder one to not fire. I could be wrong, but i could be right. Only one way to find out.



The fact that the dealership only mentioned a valve being stuck open on one cylinder also leaves me to believe that they didn’t really find any other issues, but i’m gonna give them a call tomorrow and ask just to double check.

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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[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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