Radiator busted, now misfires on cylinders 5 & 4

[80stech]

Holding means nothing, you need to check what gets into the cylinders like I told you. No need to be shy with the pressure.

[jac]

Thanks.

I left the pressure on there, with the spark plugs out, since yesterday afternoon until this morning. I used a boroscope to look into the cylinder/pistons a few times throughout and saw nothing (the pistons do look dirty with carbon build out): no oil nor coolant.

This morning, there was a loss of 1 PSI. I checked with the boroscope and still nothing. With the system still under pressure and spark plugs out, I tried to crank it several times and the pressure held and the cylinders/pistons did not have anything in them still.

[80stech]

Put new spark plugs in and go from there.

[X5chemist]

Does it have four prong plugs? I went to single tip iridium. The M54 has run great with them.

[jac]

Spark plugs on order. Yes, the ones on there now have four prongs, but I ordered the BKR6EIX this time (which has a single prong).

I also had ordered a proper smoke test machine. It arrived today, so I tested by blowing the smoke into the intake and I could not find any leaks.

[jac]

Ok, I installed the new spark plugs (NGK BKR6EIX) and went for a ride.

After some hard acceleration, the ECU now throws codes for cylinders 4, 5 and 6.

Once the errors are thrown the engine is rough (feels very wobbly) and has little power.

The errors on INPA are:

[241] Combustion misfires Cylinder 4 [CARB_A]
[242] Combustion misfires Cylinder 5 [CARB_A]
[243] Combustion misfires Cylinder 6 [CARB_A]

They all contained this:

TCO              95.25 Grad C
N_32_TOL        5952.00 rpm
MAF_TOL         463.00 mg/stk
MAF_BOL         419.42mg/stk
Occurred before (rel. BZ)  0.10h


The fault is emissions-related
Error debounced
No errors currently present
Sporadic error

[80stech]

I assume fuel is getting shut off to all 3 ? Anyway if things are that bad should be easier to find the problem. Was it fine until the hard driving? Did you gap the plugs to .032" what do they look like now? Re-doing the compression test might be a good idea but do only 4 compression strokes this time, and it's better if you can watch the tester while someone else does the cranking.

[jac]

I assume fuel is getting shut off to all 3 ?
I don't know. How can I determine if that is the case?

Was it fine until the hard driving?
Sort of, it did feel a bit off (some gears would not switch to the next gear until it had reached higher RPMs than I remember from when it worked fine), but it was not rough and it was not throwing codes. The three lights on the dash are still there (yellow triangle, yellow ABS and red Brake) constantly but I assume have nothing to do with the misfires.

Did you gap the plugs to .032" what do they look like now?
I measured the gap on all 6 new spark plugs and it was already 0.032" on each. Gonna go take them off to look at them and I'll come back in a bit.

Re-doing the compression test might be a good idea but do only 4 compression strokes this time, and it's better if you can watch the tester while someone else does the cranking.
Ok, thank you. I will try that. For my education, why 4 instead of 6 strokes?

[80stech]

The first time you posted it said "with cylinder fuel cut" but I think the actual code is the same so probably still has the "cylinder fuel cut."

I thought for sure you had the plug gap too big which is why it got worse with the new plugs but I guess not.

4 strokes is standard, if the rings are poor you will be able to tell as it takes more strokes to pump up the compression, a good cylinder will get close to max at 2 or three strokes, 6 will allow poor rings to "pump up" the gauge.

[jac]

The first time you posted it said "with cylinder fuel cut" but I think the actual code is the same so probably still has the "cylinder fuel cut."
Ah, yes. Sorry about that. Indeed the description in the other code reader (PA Soft BMWScanner 1.4) says:

F2 [242] Misfire, Cylinder 5, misfiring with cylinder cutout (Misfire CARB_A)
F3 [243] Misfire, Cylinder 6, misfiring with cylinder cutout (Misfire CARB_A)
F1 [241] Misfire, Cylinder 4, misfiring with cylinder cutout (Misfire CARB_A)

I thought for sure you had the plug gap too big which is why it got worse with the new plugs but I guess not.
None of them were past the 0.032" mark. This is probably the first time I have checked the gaps on spark plugs, so I was a bit afraid to be honest to mess up the gap so most I got to the 0.031 mark and called it good enough as the fit was already very tight on the gauge. Funny thing: I have had the gauge for 35+ years and this is the first time I have used it.

4 strokes is standard, if the rings are poor you will be able to tell as it takes more strokes to pump up the compression, a good cylinder will get close to max at 2 or three strokes, 6 will allow poor rings to "pump up" the gauge.
Ok, thanks. I thought it might be something like that but figured I'd ask.

What do they [the new spark plugs] look like now [after the test drive]?
They all look fine. They don't look sparkling new anymore, but no oil or carbon is on them.