1G Misfire on Cylinder 3 and 4

[mac 108]

Completely stock 1G turbo

Car developed a severe misfire and loss of power. Seems to be running on only two cylinders.

Plugs on cylinders 1 and 2 read fine. Plugs on cylinders 3 and 4 are black and gas soaked. While the car is idling, you can remove the plug wires on cylinder 3 or 4 and there will be no change in how it runs. Removing one of the plugs on cylinder 1 or 2 will cause the engine to die.

Stock heat range NGK plugs have less than 1000 miles on them. I have replaced the plug wires and tried 3 different coils. Compression is uniform across all cylinders at about 150 cold.

What's my next move? This car ran great then developed this problem out of the blue without warning.

 

[mitsubishikid]

could be damaged or corroded old wiring, disconnect the injector connectors, and then back probe them with a digital multimeter, all the way to the ECU connectors, and see if they all have the same resistance, to be thorough you should do this to all engine sensor wire connectors, also wiggle the harness as you check to see if any values change.

 

[gsxeclipse102]

What method did you use to check the spark? Cyl 3 and 4 dont share a coil. id lean more towards cas/wiring or injectors sticking open fouling plugs.

 

[jim95redgsx]

This does not sound like an ignition related issue to me. Except for spark plugs and wires (which you replaced), all other ignition components would cause ignition failure on cylinders 1 and 4 or cylinders 2 and 3 (NOT cylinders 3 and 4).

You could be flooding out cylinders 3 and 4 due to stuck open injectors, or more likely, a leaking diaphragm in your fuel pressure regulator.

To test this, pull off the vacuum hose that connects the intake manifold with the FPR. Preferably, do this with the engine off and pull the vacuum line off at the IM. Put the end of this vacuum line in a suitable container to hold fuel and then start the engine. You don't want to spray fuel on a hot engine if it is leaking. Depending on the location of the vacuum port on the IM, it could be spraying fuel directly into the runners for cylinders 3 and 4.

Jim

 

[mac 108]

I'll try switching injectors next.