Anonymous
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Re: Need help, 95 Montero SR 3.5 DOHC, missing
09/28/05 09:06 AM
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Wagits, not sure if I can help too much on the engine missing, it could be a number of things. It does sound more like an ignition issue than a fuel issue as you say you can smell unburt fuel.
The spark plugs on the 3.5 DOHC (as with many OHC engines) are deeply buried in the cylinder heads - they need to be as the cams and valve train sit quite high above the cylinders themselves. When you remove the plastic covers protecting the spark plugs and associated wiring, you will see 2 things:
1. On left hand (as viewed from rear of vehicle) bank of cylinders there will be the 3 coil packs bolted to the cylinder head - each of these coil packs fire the spark in 2 cylinders, so coil pack on cylinder 2 fires cylinders 2 & 5, coil pack on cylinder 4 does cylinders 1 & 4 and coil pack on cylinder 6 does cylinders 3 & 6. Attached to each coil pack are 2 wires. The thick wire is the high tension lead going to the right hand cylinder bank (1, 3 & 5) and the thin wire is the control circuit from the ignition transistor (mounted to the top of the intake plenum) - it is this circuit which control spark timing and firing order, etc. When you unbolt the coil packs you will see the high tension terminal for the left-hand cylinders (2, 4 & 6) which is the long "tube" which fits onto the spark plug. The spark plug is actually about 5 inches below the level of the top of the cylinder head!
2. In the right-hand cylinder bank you will see only the high tension leads (coming from the coil packs) which connect to the spark plug agin via a long connector.
If your problem is ignition related it could be in a number of components including:
1. Spark Plug
2. Spark Plug wire (Cylinders 1, 3 & 5)
3. Coil Packs (Cylinders 2, 4 & 6)
4. Ignition transitor
5. Engine Control Unit (computer which runs the vehicle!)
6. One of the engine sensors: Crankshaft or Camshaft Position Sensors
7. etc, etc
You can test the wires and coil packs yourself - the coil packs are expensive (about $80-100 each  )
Might also be a mechanical issue - valves, head gasket or piston rings - and a compression test migh identify a problem cylinder. As far as a fuel problem is concerned - I am honestly not sure  .
This link will take you to an article which will give you some more info on how to remove the plenum to get at the spark plugs - some folks on the Wire have said they can get all the plugs out without all this work, but I can't figure out how (they must have triple-jointed fingers  )) - you might want to take further advice on this.
I used the Chilton's manual for this - but watch out, there are some errors in it. The prime one for this job is that in the Chilton's book the spark plug wires are incorrectly numbered in one of the key diagrams.
Hope this is useful.
Cheers 
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