1996 Tracker

[Basin Hollow Rider]

After 3-4 miles of driving my 1996 Geo Tracker starts cutting out above 2000 RPM. It seems to totally loose spark for 1-2 seconds and then kicks back on. The Tachometer drops to zero during that short time and then registers again. I have partly pulled a plug wire and you can hear the spark stop during that 1-2 second break. I replaced the distributor and checked the throttle sensor to no avail. Any thoughts on this one? It runs okay under 2000 RPM but does it consistently above that RPM.

[Moses Ludel]

Basin Hollow Rider...Regarding your TPS replacement, I recently had a stall condition on the 4.0L Jeep as it transitioned to closed loop.  It was the MAP sensor.  But you describe an actual lack of spark.  That's separate from fuel flow, fuel mixture or injector pulsing.  If the tach was not dropping to zero, I'd being checking the fuel filter and fuel pump.  (They're actually worth checking, anyway.)  If you're in gear, driving along, and the tach drops to zero as the engine cuts out, either the ignition switch or coil primary are likely "open".

Often, when there is spark loss with rpm, a warmed ignition coil is defective.  The tach dropping off could indicate a primary ignition open or defective coil.  A primary ignition open would be the ignition switch or wiring from the ignition switch through to the gauges and coil...A defective coil or primary wiring open could affect the tach if the tach pickup signal is from the primary/coil.

I would isolate the 12V primary wire at the coil and run a fused jumper wire directly from the coil 12V primary lead to the battery.  Start and drive the Tracker in that mode and see if the cutting out stops.  (Disconnect the jumper after testing!)  If so, you have a defective ignition switch or wiring issue.  You know that there is an open or voltage loss/drop in either the circuit between the battery and coil or simply a defective coil.  Test the coil cold and warm.  Coil troubles often show up as the coil warms. 

If there is no spark when the engine cuts out and the tach drops off, my first concerns would be a defective ignition coil or an ignition switch with too much resistance.  Beyond this, check continuity (with a volt-ohmmeter) of the wiring, ignition switch, fuse block and connections from the battery through to the coil. 

Read voltage at the coil primary lead with a volt-ohmmeter.  Do this with the system cold, and check it when the engine warms up and would likely cut out.  Again, it is common for a defective coil, by itself, to misfire when warmed up.  If your tach signal is here, that could also account for the tach dropping to zero.  Also, a defective ignition module or wiring can cause this behavior.  Did you replace the distributor with a rebuilt unit and new module?  Check the grounds at the battery, body and engine.

Be certain you're losing spark at the plugs when the engine cuts out.  If spark is not the issue, the fuel filter, pickup sock in the tank and fuel pump would be on my troubleshooting list.

Let us know what you find...  

Moses