86 720 4x4...misses...looking to solve this!

[fredT]

I've owned this truck for around 15 years and 22K miles.  Has always been reliable till now.  I currently use it for a backup vehicle to drive if needed while fixing current ride.  Been driving it through a full tank once a year to be sure it still runs OK...refill the tank...add Stabil and it usually sits for a while.  Has around 237K miles on it.

 

Last time I drove it any distance it was running on maybe 3 cylinders.  This is the Z24i...first year of the fuel injection system.  Have the FSM and the Z24i extra manual.

 

Have replaced the dist cap and wires. Checked the exhaust side plugs and cleaned them.  Am going thru vacuum lines and looking for leaks.

 

Have a vacuum gauge in the truck and it seems to vibrate the needle when under 2000 rpm or there about.   At one point it seemed to clear up now and then where the needle stayed steady for short periods of time.

 

Looking for a hint or info from someone who knows these trucks and might have an idea where to look.  Thinking the rotor/LED at the bottom of the dist (have another dist that I think is good) or maybe a fuel issue...running lean...vacuum issue?  Fuel filter or fuel pump?

 

 

 

[datzenmike]

Check and set the valve lash. Just to be sure.

 

Check that the throttle body is securely bolted to the intake.

 

Remove the EGR and wire brush it clean. Make sure it can close properly. If deposits and preventing it from closing fully it will leak exhaust in at idle when it should be closed.

 

 

The Z24 is notorious for blowing head gaskets. You may be in the early stages. Try re-torquing the head bolts. This must be done on an absolutely COLD engine. In any order... loosen just ONE bolt and immediately tighten to 60 foot pounds with a torque wrench. Only when tight move to the next bolt. This will assure that the clamping force on the gasket is renewed. Do this once a year.

 

If the gasket is slightly compromised this may not fix the problem but no harm in trying.