Cylinder 3 Misfire Diagnosis (1 Viewer)

[Supra88]

No trouble, just wanted to be sure I understood you.

A leak down test might be the next thing to do....but if it were me....I'd pull the cams, re-torque the studs and then perform the compression test across all cylinders. If no changes....then leak down.

I was thinking the same thing. The fact there's low compression on 2-6 made me think the head is lifting potentially from insufficient clamping force. I need to swab cylinder 4 to see why it's wet. The other cylinder tops look almost too clean as if they're seeing coolant.

 

[flintknapper]

I was thinking the same thing. The fact there's low compression on 2-6 made me think the head is lifting potentially from insufficient clamping force. I need to swab cylinder 4 to see why it's wet. The other cylinder tops look almost too clean as if they're seeing coolant.

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Yes Sir......believe you are on the right track. Let us know.

 

[Supra88]

Yes Sir......believe you are on the right track. Let us know.

Couple of updates here. I have everything stripped down and at TDC to begin the process of removing the cams. The plan is to retorque the ARP hardware in the OEM tightening sequence. Crack the nut loose 1/2 turn and retorque to xx ft-lbs one stud at a time. I may go back through a second time like OTRAMM does to verify torque, but just tightening. I plan on marking the radian of the nut before I turn it ot see how much movement I have. ARP calls for 80 ft-lbs and this is likely where they were originally set 100k+ miles ago. Should I go higher?

I'm speculating that the hardware loosening is the problem. I should know once I start turning bolts. Is there a good test to see If I've sealed the head minus putting everything back together? Should I baseline anything with the leak down tester now?

 

[ppc]

n/a

 

[Supra88]

I have an interesting update. I pulled the cams and performed a leak down test (75 psi regulated inlet pressure). Here are the ACTUAL resulting cylinder pressures (psi):

cylinder 1: 51
Cylinder 2: 28
Cylinder 3: 19
Cylinder 4: 20
Cylinder 5: 25
Cylinder 6: 22


Percent pressure loss:

Cylinder 1	32%​
Cylinder 2	63%​
Cylinder 3	75%​
Cylinder 4	73%​
Cylinder 5	67%​
Cylinder 6	71%​

no air flow in the coolant, exhaust, or intake, however there was substantial air leakage on adjacent cylinders (out of spark plug holes). I'm going to retorque the cometic MLS/ARP hardware today and retest.

Thoughts?

 

[flintknapper]

So basically only cylinders 3,4 and 6 (marginally) are acceptable.

So Yes......re-torque and re-test.

 

[Supra88]

So basically only cylinders 3,4 and 6 (marginally) are acceptable.

So Yes......re-torque and re-test.

Actually, no. Those are the resulting cylinder pressures. These are the leak down losses:

Cylinder 1	32%​
Cylinder 2	63%​
Cylinder 3	75%​
Cylinder 4	73%​
Cylinder 5	67%​
Cylinder 6	71%​

 

[Supra88]

Update: I retorqued the head to 90 ft*lbs and reran the the leak down test. I got really excited when my cylinder#1 leak down percent went from 32 to 7! Until I did the other the other five cylinders. Here's what they look like now (Percent leak down loss):

	Loss
Cylinder 1	7%​
Cylinder 2	69%​
Cylinder 3	79%​
Cylinder 4	72%​
Cylinder 5	65%​
Cylinder 6	71%​

I think it's time to pull the head to see what's going on.

Also, cylinder #2 is communicating with cylinder #3. Cylinder #3 is communicating with cylinder #2 and #4. Cylinder#5 is communicating with cylinder #6.

 

[flintknapper]

Actually, no. Those are the resulting cylinder pressures. These are the leak down losses:

Cylinder 1	32%​
Cylinder 2	63%​
Cylinder 3	75%​
Cylinder 4	73%​
Cylinder 5	67%​
Cylinder 6	71%​

Leak down loss (percentage) over a specified period of time is the only thing you are looking for AFTER a compression test. That and listening for air escaping.

Looks like you have leakage between cylinders. Hopefully you will not find 'flame cutting'. IF the stud torque was insufficient AND it has been that way for a period of time....you might have real troubles.

 

[Supra88]

Leak down loss (percentage) over a specified period of time is the only thing you are looking for AFTER a compression test. That and listening for air escaping.

Looks like you have leakage between cylinders. Hopefully you will not find 'flame cutting'. IF the stud torque was insufficient AND it has been that way for a period of time....you might have real troubles.

I'm wondering if the block wasn't prepped well enough for the MLS gasket? I initially retorqued to 80 ft-lbs and the radian I marked
lined back up perfectly. None of the nuts/studs felt like they were loose.
When I retorqued my ARP hardware/MLS on my Supra I got a lot more movement.

 

[flintknapper]

I'm wondering if the block wasn't prepped well enough for the MLS gasket? I initially retorqued to 80 ft-lbs and the radian I marked
lined back up perfectly. None of the nuts/studs felt like they were loose.
When I retorqued my ARP hardware/MLS on my Supra I got a lot more movement.

The Ra for MLS gasket is much different than that for traditional gaskets, so YES....if the block and head were not properly prepped....expect problems at some point.

 

[SNLC]

Code states cylinder 3 misfire. I verified that I have spark on plug #3.

Go through the diagnostics in the FSM for the ignition system. Start with CPS, move to dizzy, wires, plugs, igniter and so forth.

Simple test for the ign system as shown in the fsm using a volt meter. You can also test the injectors.

Cheers

 

[Supra88]

Go through the diagnostics in the FSM for the ignition system. Start with CPS, move to dizzy, wires, plugs, igniter and so forth.

Simple test for the ign system as shown in the fsm using a volt meter. You can also test the injectors.

Cheers

I did that per fsm before I tested compression and performed a leak down. Also checked injectors.

the leak down confirmed there's communication between the cylinders which leads me to believe it head gasket resisted. Head is coming off to inspect.

 

[Supra88]

Update after pulling the head. The MLS HG catastrophically failed between 2-3, 3-4, and 5-6. There is evidence of a lesser degree of failure between the other cylinders. Any guess on why this would happen?

 

[BILT4ME]

Update after pulling the head. The MLS HG catastrophically failed between 2-3, 3-4, and 5-6. There is evidence of a lesser degree of failure between the other cylinders. Any guess on why this would happen?

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Maybe deck surface Ra not smooth enough, allowing coolant tracing between cylinders, then eroding it to kill the fire ring....?

 

[flintknapper]

Better pluck that gasket and look for 'flame cutting'. That is pretty much what I expected to see.

Cause? Hard to say.

Possibly incorrect Ra (metal gaskets need a very smooth and flat surface). Improper torque (who knows).

Personally, I wouldn't use a MLS gasket and studs unless I was going to 'boost' the engine.

Glad you got it figured out, but sorry to see it was a worse case scenario.

 

[Supra88]

Maybe deck surface Ra not smooth enough, allowing coolant tracing between cylinders, then eroding it to kill the fire ring....?

I think that's a good guess, especially since it's across all cylinders.

im going to put an OEM HG on it and leaning towards using the ARP studs.

 

[Supra88]

Better pluck that gasket and look for 'flame cutting'. That is pretty much what I expected to see.

Cause? Hard to say.

Possibly incorrect Ra (metal gaskets need a very smooth and flat surface). Improper torque (who knows).

Personally, I wouldn't use a MLS gasket and studs unless I was going to 'boost' the engine.

Glad you got it figured out, but sorry to see it was a worse case scenario.

The block looks like it has some soot build up but no steel missing. I think it's going to be okay, but I'll get a closer look at it tomorrow.

 

[ppc]

I would be more concerned with flame cutting on the sealing surfaces on the aluminum head.

 

[flintknapper]

I would be more concerned with flame cutting on the sealing surfaces on the aluminum head.

^^^^

Yep,

It's actually the more likely of the two to show damage, but more easily repaired.

Hard to imagine that the gasket would be that badly compromised (between cylinders) and there NOT be some erosion/flame cutting to the block deck or head.....but I've seen some strange things before.

Let's keep our fingers crossed. OP has had enough trouble already.