N12 Nightmare cylinders 1&4 misfire after head gasket replacement
#1
N12 Nightmare cylinders 1&4 misfire after head gasket replacement
Hi. This is my first post here, looking for help with a never ending problem.
Warning: Long winded and frustrating
I own a 2007 hatchback with an N12 in it. The head gasket went out last year and caused misfires and rough idle to the point it was undrivable. so after a long and difficult teardown the gasket was replaced and the engine reassembled. the car refused to start. Ive triwd simple things like replacing the gas as it sat for quite a long time. Nothing.
The engine was reopened and all sensors and wires inspected. The timing was recheckedand verified and during the inspection a small fuel pressure was found. all injectors seals were replaced along with clips. the engine still had a misfire in cylinders 1&4. At this point I brought in a mechanic to look at the car and it was found that 3 of the hydraulic lifters were bad, and were replaced. after the cams and variable intake side was reinstalled, the misfires still persist.
After vigorous cussing, I purchased a leak down tester and went to work on testing all cylinders. The results are:
Cyl 1: 65percent leak with a small amount of air making its way into the intake manifold and also leaking through the oil drain holes below the cam
cyl 2: 22 percent leak couldnt pinpoint a source and cyl still generatss combustion
cyl 3: 30 percent leak same as cyl 2
cyl 4: 58 percent leak from the oil drain holes under intake cam
The injectors are delivering fuel and all the coilpacks and sparkplugs are still firing. I am at the point where I do not know how to procede with the project. I really want to get this car working for my woman, she loves the car and is the only reason I havent dumped the car yet.
Any ideas or assistance would be immensely appreciated, thanks.
Warning: Long winded and frustrating
I own a 2007 hatchback with an N12 in it. The head gasket went out last year and caused misfires and rough idle to the point it was undrivable. so after a long and difficult teardown the gasket was replaced and the engine reassembled. the car refused to start. Ive triwd simple things like replacing the gas as it sat for quite a long time. Nothing.
The engine was reopened and all sensors and wires inspected. The timing was recheckedand verified and during the inspection a small fuel pressure was found. all injectors seals were replaced along with clips. the engine still had a misfire in cylinders 1&4. At this point I brought in a mechanic to look at the car and it was found that 3 of the hydraulic lifters were bad, and were replaced. after the cams and variable intake side was reinstalled, the misfires still persist.
After vigorous cussing, I purchased a leak down tester and went to work on testing all cylinders. The results are:
Cyl 1: 65percent leak with a small amount of air making its way into the intake manifold and also leaking through the oil drain holes below the cam
cyl 2: 22 percent leak couldnt pinpoint a source and cyl still generatss combustion
cyl 3: 30 percent leak same as cyl 2
cyl 4: 58 percent leak from the oil drain holes under intake cam
The injectors are delivering fuel and all the coilpacks and sparkplugs are still firing. I am at the point where I do not know how to procede with the project. I really want to get this car working for my woman, she loves the car and is the only reason I havent dumped the car yet.
Any ideas or assistance would be immensely appreciated, thanks.
#3
I built a crank locking pin and cam locks to put the car back together, trying to save money incase I have to replace more expensive parts. So far I have not done a compression test, it was apparent the cylinders had low compression just by covering the spark plug holes of cylinders 1 and 2 at the same time and feeling the difference when cranking the starter.
when the doors are opened there is a brief humming which I am assuming is the fuel pump. The gasket on one of my injectors was bad and sprayed fuel everywhere so i know fuel is moving to the injectors. when attempting to start, the plugs for 1&4 will be wet with fuel , it just isnt getting combustion. 1&4 on the exhaust manifold are cold to the touch while 2&3 will be warm.
when the doors are opened there is a brief humming which I am assuming is the fuel pump. The gasket on one of my injectors was bad and sprayed fuel everywhere so i know fuel is moving to the injectors. when attempting to start, the plugs for 1&4 will be wet with fuel , it just isnt getting combustion. 1&4 on the exhaust manifold are cold to the touch while 2&3 will be warm.
#4
On timing job, when you turn your crank to align flywheel into locking position for the insert key, did you also open up all spark plug holes and place equal height long sticks like zip-ties or kabob sticks? you need to check piston height as you turn the crank. The key can be inserted into lock position at 0 and 180 degrees of crank position. And depending on which one you're in, you could have completely missed the timing with the cams. I can be wrong as this is what I've been doing with the N14 engine, not sure if N12 would be same but it's good to think about that and check it. I did see others perform their timing job and missed it this way.
#5
#6
Look, I rebuilt a dozen of these engines and not a single one had "two locking holes"!!! UNLESS you have an after market flywheel. So, to test the locking holes, count how many times it locks the flywheel and at what piston level.
once you lock the crank shaft, then you need to make sure the cams are facing up where the locking tool would sit snug.
try to do it the way you did it before and post pictures
once you lock the crank shaft, then you need to make sure the cams are facing up where the locking tool would sit snug.
try to do it the way you did it before and post pictures
#7
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#12
#14
when performing the leak down tests, most of the leaking was happening through the intake side. After inspecting I found there is one bad valve in each of the misfiring cylinders. There was a small air leak coming from the oil drain holes under the valve cover leading me to believe the rings are worn out. The motor has 220K on it. Im just trying to avoid opening up the nightmare machine again in the near future.
#16
when performing the leak down tests, most of the leaking was happening through the intake side. After inspecting I found there is one bad valve in each of the misfiring cylinders. There was a small air leak coming from the oil drain holes under the valve cover leading me to believe the rings are worn out. The motor has 220K on it. Im just trying to avoid opening up the nightmare machine again in the near future.
#17
After searching for ever. I finally found the source of all of my woes. The valve seat in my number 4 cylinder dropped out and was crushed into little pieces and spread throught my cylinders. It no longer sealed on the number 4 and a large piece traveled through into the number one and was crushed into tiny pieces which got stuck in the piston rings and into the valve seals. Amazingly the cylinder walls are still intact and have no scratching. my piston rings and pistons werent so lucky, the pistons have marring on the top surface from the metal pieces and my piston rings came out in pieces while cleaning out the cylinder bores.I have a machine shop set to do the new seat next week. all the exhaust valves and the intakes in 2 and 3 are still sealing perfectly. I may reseal them when putting the head back together. Hopefully this is it.
#18
#19
Ive got new valves coming with a tool and im planning to lap them all in after the seat gets replaced. Ive pulled all the ring sets and am planing to rehone the inside to get the cross hatch back. Theres no vertical marks so I shouldnt have to get too agressive with it. just wanna make sure that when i get all the parts back together I dont have to reopen the nightmare machine again for a good while.
#20
After searching for ever. I finally found the source of all of my woes. The valve seat in my number 4 cylinder dropped out and was crushed into little pieces and spread throught my cylinders. It no longer sealed on the number 4 and a large piece traveled through into the number one and was crushed into tiny pieces which got stuck in the piston rings and into the valve seals. Amazingly the cylinder walls are still intact and have no scratching. my piston rings and pistons werent so lucky, the pistons have marring on the top surface from the metal pieces and my piston rings came out in pieces while cleaning out the cylinder bores.I have a machine shop set to do the new seat next week. all the exhaust valves and the intakes in 2 and 3 are still sealing perfectly. I may reseal them when putting the head back together. Hopefully this is it.
?
#21
When the seat dropped it destroyed the inside of the head in all of the cylinders on mine, as well as the piston heads and rings. I decided against repair at that point as a motor from a dismantler was 1k cheaper than parts to fix the motor. If you decide to go with repair. I recommend finding a engine or metal shop to do it for you. They will remill the head and custom make a hardened steel valve seat and ensure they’re properly fitted and done. At that point though all of the seats should be redone to prevent another one from dropping out in the future. The shop quoted me $400 to do the valve seats. That price doesn’t include filling in and remilling the indentations in the head caused by the old valve seat being crushed into little shards.
#22
When the seat dropped it destroyed the inside of the head in all of the cylinders on mine, as well as the piston heads and rings. I decided against repair at that point as a motor from a dismantler was 1k cheaper than parts to fix the motor. If you decide to go with repair. I recommend finding a engine or metal shop to do it for you. They will remill the head and custom make a hardened steel valve seat and ensure they’re properly fitted and done. At that point though all of the seats should be redone to prevent another one from dropping out in the future. The shop quoted me $400 to do the valve seats. That price doesn’t include filling in and remilling the indentations in the head caused by the old valve seat being crushed into little shards.
#23
The shop custom makes them to ensure they’re a perfect fit. Most engine and metal shops can make them for you. Then the head is milled so they fit together perfectly. A stock valve seat can’t go into the space where the old one dropped out as it wouldn’t fit right enough in the old slot. The shop I contacted makes the valve seats a few microns larger then presses them in so they’re mated almost permanently.
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