FTO AUSTRALIA

I picked up a new multimeter today and wanted to test the coils off my Mrs' Pajero to check for that misfire issue.
(Although there is no stutter while driving, I can sometimes see the rpm needle take a quick dip while idling.) Just wanted to make sure if the coils are ok anyways.

So according to my engine's manual, and Bennoz's link (http://www.ehow.com/how_4912368_check-c ... meter.html) this is what I am doing:

Engine Manual:


The Coil in question:


To get the primary resistance of the coil am touching the middle pin and the 3rd pin in the plug A as named in the diagram. (Reads .578 k ohms)
To get the secondary resistance of the coil am touching the Spark Lead connector C and the Spark Plug connector B metals. (Reads 10.3 k ohms)
(Both measurements are taken on an autorange meter)

Am I doing it the right way?
So according to the manual my primary resistance should be between .7-.86 ohms and secondary resistance should be between 11.3-15.3 k ohms. My readings are lesser than that, therefore my coil is bad?

This is my first time with a multimeter and learning things..so sorry for the noob question

Well to start the pic you have out of the manual is not the same as the coil you have.
The manual is showing a complete coil pack which would be bolted beside the engine and have 4 leads running to the 4 spark plugs.
The coil you have is like the FTO ones that sit above one sparkplug and run a lead to a second spark plug.

You must have the wrong manual.

Hmmm... yeah sensed something was odd in that picture. Had searched for 4G93 1.8L 4cyl SOHC and that's the result I came up with..apart from the other ones with 6 cyl.

Is my method of testing the resistance correct though?

Yes your method is correct, but you need to find out the actual pins/terminals to test and the correct specs.

Thanks mate. All the manuals am finding now have coil-on system. :\
Urgh!! Off to the abyss of Google search

Btw, this is a SOHC and not a DOHC right?
(couldn't see any groove in the middle of the cam head like DOHC engines usually have)

Yes it is a SOHC as there is only one cam pulley as you can see from the timing belt cover.

Thanks

Hey Phil,
Is this what am after?

Does match the engine specs and coil/lead wire type.

That looks like it.
Is it for your engine?

The "secondary resistance " you have already done is in specs

The primary coil check, you will need to connect a "AA" battery to "2(-)+3(+)" and read the continuity across "1+2" should be 000 or not far above and your multimeter should "alarm".
Disconnect the "AA" battery and you should not have any continuity.

Manual said 4G93 SOHC, only thing it said was 2002 M/Y... which I think is for a 2002 model But that's the only one out of 8 Pajero IO manuals I downloaded which matched the coil and spark lead combo
Whew so secondary resistance was all good

I put the coil back on before I saw your post but I had done this test yesterday:

Checked continuity/resistance between 1 and 2....got OL and no beeps, checked continuity between 2 and 3 got .578 k ohms, checked continuity between 1 and 3 got OL and no beeps. (This was on an autorange, so definitely didn't matter if I had a lower range selected).

This is what I understand from the test, correct me if am wrong -->

2 and 3 has a working circuit with some resistance hence my continuity test worked giving me the result of .578 k ohms; and connecting the 1.5v battery on 2 and 3 passes power through them. 1 and 2 do not form a complete circuit unless you manually connect those two points and have a battery (some form of connection) on 2 and 3. This completes the circuit between 1 and 2 and 3. Disconnecting the circuit between 2 and 3 (with the battery in this case) will also break the circuit between 1 and 2 or 1 and 3.

It's like a relay or switch
Power (battery) to 2+3 switch is closed (turned on) = continuity (flow) 1+2
No power to 2+3 switch is open (turned off) so NO continuity (no flow) 1+2

Ah..makes sense
Thanks mate. I will pull it out and check it again.

The ECU will send 1.5v to 2+3 to activate coil (send specified power to coil and onto spark plug through 1+2), then ECU will send no power to 2+3 to stop spark.
This will happen constantly (on,off,on,off....) as the ECU wants each plug to spark

So there wouldn't be any way where I can change all the 4 as coil on spark instead of the current coil and lead system? I would need to alter how the ECU handles and fires the spark? I have heard all coil on spark plug systems have better spark/ignition than the ones with lead wires branching off from a coil?

Unsure, may need to ask an auto electrician.

I would assume you would have to change the ECU and wiring too, but don't quote me on that