HELP: Not your normal Head Gasket issue, 99 EXP w/ 230K miles

[craiganator]

Do you agree the head gasket is the issue?

Facts:
99 Ford Explorer
230K miles
4.0 SOHC
No Oil burning
Minor oil leak from oil pan gasket
No coolant leaks
No coolant mixed with oil
Was running normal until one cold morning ~ 35 degrees F
Started skipping and surging
Threw codes P0171 and P0301
Started diagnostics and confirmed it has fire, fuel, compression, fuel pressure, good injectors, good MAF, good O2 sensors but short term fuel trim on Bank 1 was cycling with a frequency much higher than Bank 2. Checked for vacuum leak via the smoke test. Pushing smoke through the vacuum lines looking for leaks showed a leak in between the head and block on Bank 2. We isolated the test by making the smoke input be the crankcase vent on the passenger side(bank 1). (with engine not running) the test smoke travels through the crankcase and only comes out in between the head and the block near the front on Bank 2 (drivers dside)as shown in the video. Does this mean the head gasket is open to the atmosphere and is the air leak? Yet sealed enough to maintain oil and coolant where it is suppose to be?

http://youtu.be/UIsgDTdmC0M

Just hard to believe that the head gasket needs to be replaced since it has compression and no water in the oil or heavy steam coming out the exhaust.


Long story less long...Please advise if this has been seen before and what was done to remedy.

Many Thanks.



p.s. I searched for a while to see if this had came up, but there were all kinds of "its your intake gasket" threads for the P0171 code.

 

[my98nnj]

Replace the INTAKE MANIFOLD gaskets, not the head gasket.

 

[craiganator]

Thanks for the reply. The intake is off of the block and it still leaks smoke in between the head and the block. This tells me what to do, yet not necessarily the rationale. Would it be possible to explain the reasoning how the intake gasket was determined the issue? At this point, the intake gasket is much easier to change than the head gasket. It certainly is worth a shot, although I will be surprised if that fixes it.

 

[craiganator]

Update: changed the intake gaskets. No change to the skip or the short term fuel trim Bank 1. short term fuel trim bank 1 is more erratic and above the 25%+ and bounces up and down more than Bank 2 short term fuel trim.

Next step?

 

[craiganator]

Any ideas why the STFT for Bank 1 is so erratic?

 

[koda2000]

if you blow smoke into the crank case and its comming out between the head and the block it must be a head gasket issue. have you done a compression test? a blow head gasket will not always leak oil or water. it depends where the break is.