WestEnd

OK guys, I need your help. Never done a compression test before, so I'm not sure I did it right.

1998 Tacoma with the 2.7L and 5-speed.

Warmed truck up for about 3 or 4 minutes. (enough?)

Cylinder 1- 135psi
Cylinder 2- 149psi
Cylinder 3- 150psi
Cylinder 4- 147psi

• I have a MIL code of P0301... Engine Misfire #1.
• The #1 plug is black, but not wet.
• The rest look almost new.
• Passenger side of block is obviously leaking coolant
• and maybe even oil. (oil pan gasket?)
• Radiator was low on coolant (couldn't even see it)
• Can't tell where it's coming from
• Engine backfires when you give it throttle.

I'm leaning towards a head gasket, with the coolant loss and fouled plug and #1 misfire.

Any other thoughts??

If it is a head gasket, with those Compression readings, should I look for a different motor?

Thanks for the help!!

WestEnd

Oh... I forgot... During compression test, I held the throttle wide open and cranked it two times for about half second each crank. Is that proper ?

zlathim

When I check compression, I usually let the engine crank for 4 or 5 complete revolutions. You may have shorted yourself a little, but the numbers don't seem to reflect it.

I would perform a cylinder leak down test next. If it is a HG, you will get air leaking through the cooling system. Look for bubbles in the radiator.