Head Gasket?
 

Well... I recently had some issues with my motor. The truck is a 1997 Tacoma, 3.4L V6. Around 90k miles. The problem started in the morning when it was still cold outside. The motor felt like it was shaking a bit, you could feel it in the shifter. It went away when warmed up. It did this in the morning, or when first starting up the truck a few times in the week until the check engine light came on and I took it to my mechanic. The scan came up with a misfire on #4 cylinder, and we decided it was either the coil, or a head gasket issue. We switched the #4 coil with another coil, to judge whether or not the coil was bad. Since then the check engine light has not come on so I have not been able to scan it. The motor still runs a little rough but not as bad. What would the symptoms be if it was the head gasket?

Please help me out with suggestions, you can ask me questions, etc. (I am no mechanic but I try, haha)

Thanks for the help

i would suspect the easy things first.
Plugs, spark plug wires, coil.

If you suspect the head gasket, do a compression test, 2 cyl next to eachother that are considerably less then the rest would indicate a failing head gasket. That being said...I agree with j-man, check the easy stuff first.

Its a Toyota engine with 90k on the clock? its just breaking in! ;)

The probablilty of it being a blown head is pretty slim. Unless you overheated the engine, or was running it really hard, I wouldn't really think twice. You could do a compression test yourself and if there are 2 cylinders next to eachother that are low, it may be a sign of a blown head. Another often symptom is oil in the water, or water in the oil, so just check that. (Your oil would look white).

Yea, I believe it is the coil myself. Ill probably replace it and see if it solves the problem. Ill keep the thread informed on the progress.

True...but I have seen a few blown heads, where there was no sign of oil in water, or vice versa...best way to determine is a compression test, or have the rad tested for cumbustion gases.

True...but I have seen a few blown heads, where there was no sign of oil in water, or vice versa...best way to determine is a compression test, or have the rad tested for cumbustion gases. And x2...I would doubt the h/g's are gone at 90k...stranger things have happened tho!

Could be a bad fuel injector.

Could be a bad spark plug.

Could be a bad spark plug wire

PROBABLY NOT the coil. One coil fires 2 cylinders. If a coil goes, BOTH cylinders will not fire.

Could be a intake manifold leak.

The "mechanic" you took it to is not much of a mechanic.


First thing, replace the plugs. Swap coil WIRES and see if problems follows the wires.

Ok so it still has a mis-fire on cylinder 4. (After swapping the coil) Next I guess I will replace the plugs. (Plug appears to be ok)

BTW, the problem def. starts when the motor is cold.

Awesome news! I went ahead and changed the spark plugs and wires and it fixed my problem!

Goes to show, never skip the minor stuff...

Thanks for your help everybody!