Igniter Problem

[Von]

Have a 93 LS400 with a 150k. Two owner dealer maintained car. It sat for 3 or 4 days during snow. Took it for a 100 mile trip and after about 30 miles it started slowing down as if out of gas, then it would pick up for 5 sec. die for 5 sec. This went on for 30 min. Turned around to come home and it cleared up. Question: Do the igniters go slowly or all at once. Also, what else besides fuel filter, water in the gas, etc.etc. would cause the engine to die as if someone were turning the key on and off.

[jeffls400]

All cylinders rely on the same igniter, so if you are having an issue where you go from 8 cylinders to 4 cylinders, I would bet it is one of the two ignition coils, or perhaps the cables associated with them.

[skokita1990-400]

not ture, there are 2 igniters, one for the LH coil and one for the RH coil.

[steve2006]

The ignition coil on the passenger side is a common cause and also check the lead from the coil as it passes through the plastic cover there should be a grommet to protect the wire but this commonly gets missed out as it is not easy to fit,this can result in the wire being damaged.

[steve2006]

not ture, there are 2 igniters, one for the LH coil and one for the RH coil.

You are right,they are mounted under a plastic cover attached to the drivers side of the engine compartment and welcome to the LOC.

[RDM]

Agreed, two coils fired by two igniters. A coil can become worse due to heat/vibration, giving you the on/off symptoms you describe.

[AndyLowe]

Agreed, two coils fired by two igniters. A coil can become worse due to heat/vibration, giving you the on/off symptoms you describe.

Von, I'm curious if you solved your Igniter Puzzle?

My 94 LS400 had a bad ECM (Power Train Computer Module) as it would have erratic voltages to the passenger side Igniter when key was on (no need to put key in Start position). My ECM would instantly rise to 2.2vdc, for Igniter 2, when key was ON, and this was wrong. When you turned the key to start, the voltage would drop to zero and occasionally have a square wave output from the ECM of 2 volts, but not nice and even like the output to Igniter # 1.

You can swap the harness connectors at the Igniters, to eliminate if you have a bad Igniter. My problem was no spark on the passenger side of the engine, and a new coil and Igniter did not fix this. When I monitored and compared signals from the ECM to both Igniters, I saw the difference.

Opening the old ECM revealed a couple leaky Capacitors, but who really knows if that was the cause. I suspect a poor transistor moreso.

I bought a ECM from a Salvage yard for $50 and it started right up.

Andy