Aggie_Grad_12

2003 AP1 with 93,000 miles. Upgraded to AP2 retainers and did a valve adjustment at 70,000 miles. Other than that no major modifications.

Last week I got P0302, P0304, and P1399 Misfire 2, 4, and random. I checked valves, all were within tolerance so I did a compression test

1 - 220
2 - 110
3 - 220
4 - 225

First thought was that it was odd that cyl 2 had low compression but not 4. Is is possible that 4 had a misfire because 2 was misfiring?

I put some oil in cyl 2 and redid the compression test, still 110. I ruled out the piston rings with this test.

I did a leak down and didn't feel any air coming out of the exhaust or the intake so I ruled out valves leaving me with the head gasket as the culprit.

I pulled the head yesterday and didn't find anything wrong. Coolant was clean, head gasket did not have any obvious leak path, and the head and block face did not have any blow-by. What is my path forward from here? I would hate to put the entire engine back together and not fix anything.

Below are pictures of the block and head. Could the miscolored valve on cyl 2 exhaust side be a burnt valve? I thought it was odd that it looked different than all the others.

Slowcrash_101

I would remove the valves on cyl 2 and inspect the valve faces, and also if the valves are straight. If you've eliminated the pistons as culprits, then it's likely valvetrain related. Since you already checked the valve clearance, then it's either the valves themselves, or a very stretched timing chain(unlikely). It wouldn't be ignition related, unless it was a loose spark plug, which might explain your cylinder 4 misfire, but wouldn't explain why cyl 4 or cyl 2 had different compression and the other tested fine. How does the cyl 2 wall look? I would send out an oil sample, that will tell you if there's any coolant in the oil which would indicate a head gasket problem.

If it's just the valves, then replace the valves. Before removing, check the valve stem installed height it should be no more than 1.76" on the intake, and 1.767" on the exhaust. Do this with new valves as well. Check the valve guide clearance before you remove the old valves. If you do install new valves, check the valve guide clearance on the new valves as well. This is done by sliding the valve out about 10mm, or a little over a third of an inch from the guide, and rocking it back and forth against a dial indicator. .006" on the intake and .009" on the exhaust, if you divide by half you'll get the actual clearance from the stem to the guide. If it exceeds this you will need a new guide, but it's not likely from the picture, unless the valves are horribly bent.

You'll may also have to recondition the valve seats to properly seat your new valves. A machine shop can do this, or you can do it yourself if you have the tools. It's actually quite amazing what Honda did to the valve seat from the factory, giving us a 4 angle valve job that gives good venturi as well as coanda effect. If you are going to do it yourself, you'll need a cutter with various angle stones, I would just send it to get machined, but then again I know a good machine shop who will do the complex angles. The angles are very specific with the angle closest to the piston at 40 for intake and 30 for exhaust 45 for the seat, followed by 67.5, and finally 82.5 before going the full 90. If you do a half assed 3 angle 30 45 75 to radius job you're gonna lose power.

Get the head machined if needed(.008" is the mill limit), check block straightness as well, just in case. Line up your cam with your crank, and button it all back together with new head bolts if your old ones are stretched beyond spec, and obviously a new gasket. Bolt thread diameter should not measure less than .45" when measured 2" from the bottom, and 1.75" from the bottom. If they check out, tighten your reused bolts in two steps, not three like for new bolts.

Idk it seems you have your work cut out for you.

Aggie_Grad_12

I found a machine shop close by that the Honda dealer recommended. Guy was very knowledgable about the engine so I'm taking the head to him tonight. Should just be 2-3 days to get it turned around and hopefully I'll get it back on the road this weekend. If he can't find anything wrong with the valves or seats then I'm really in trouble. I'm going to take him the bolts too so he can tell me if I can reuse them.

Do I need to replace intake and exhaust gaskets too. I bought the exhaust one planning on leaving the intake on the head.

Cylinder 2 wall looks fine as do all the cylinder walls. I made the mistake of draining the coolant into my oil pan but it was clear coming out so I'm pretty sure there was no oil in it.

Slowcrash_101

You can reuse both ex manifold and in manifold gaskets, you cannot re-use the head gasket, make sure you use a small bead of Honda bond/permatex where the chain case meets the block, and when you place the head gasket add another tiny bead of hb/permatex 1/5" from the edge of the head gasket around the chain case. And obviously clean all mating surfaces before applying, a lint free rag soaked in hot soapy water works best, or a cleaning solvent at most. Never use a wire brush, or metal scraping tool, aluminum is weak, you can use a plastic spatula at most.

windhund116

" I did a leak down and didn't feel any air coming out of the exhaust or the intake. "


Cylinder #2 held pressure, on the leak-down test?
.
.
.
.

Aggie_Grad_12

Cylinder 2 was far from holding pressure I just didn't feel it coming out of the pipes. I had a tiny compressor thought that only went to 75 psi.

I took it to the shop yesterday and the guy put the head on it's side, filled the exhaust with water, and it started leaking out the discolored valve in 2. He is going to check all the valves and replace any that look bad along with resurface any seats that need it. Should have a functioning head by Friday or early next week.

Now if only I can remember how to put it back together.