My son just purchased a 1990 Wrangler with a 2.5 4 cylinder. We noticed that it had oil leaks and coolant leaks that needed to be addressed. So we replaced the radiator hoses, heater hoses, heater core, thermostat, and thermostat housing. As we were bringing the Jeep up to temperature to ensure there were no leaks from the hoses we had just replaced, the engine died, as if it had ran out of fuel. The gauge read 1/2, but to be safe, we added fuel and tried to start it. No start.
I checked for spark, and we had spark. I pulled the spark plugs out of the engine and cranked the engine over. I noticed a large amount of fuel pouring out of the back cylinder.
I checked this site for values on different sensors so that I could check them one by one. I tested the MAP sensor, voltage read 5 volts in, 4.85 volts out. I tested the TPS, seemed to test OK. I unplugged the fuel injector that rests on top of the throttle body. I ohm'd it, got a reading of 2.5 ohms. I purchased a remanufactured injector from the parts store and ohm'd it, which I received the same 2.5 ohm reading. I replaced the injector with the remanufactured one, no start. I unplugged the injector and the engine started for a few seconds, presumably from the fuel that was left in the throttle body. I could repeat this by keeping the injector unplugged and using starting fluid to run the engine. Seemed to run fine.
Being absolutely stumped, I read about the MAT sensor acting similarly to a Mass Air Flow sensor. I replaced the MAT sensor with one that Car Quest cross referenced as being the right one. The sensor itself looked right, but the connector was different. I purchased a new pigtail and wired it in. After doing so, the Jeep started right up and ran. I drove it for about 5 miles before it died. Same symptoms: seemed to be over fueling. I read more information about the Coolant Temperature Sensor, which I was able to finally locate it on the under side of the intake manifold. I noticed the CTS had bare wires near the sensor. I ohm'd the CTS which ohm'd out at 8,000 ohms. I ohm'd the new part which ohm'd at 6,200. I replaced the CTS along with the MAT sensor (which I had warrantied out at Car Quest). The Jeep started right up. I drove the Jeep for approximately 5 miles with no issues. I started it up the next morning. I thought everything was fixed until I went to start it up later in the day. It failed to start again. Same symptoms: over fueling. I thought the CTS with the bare wires was the smoking gun. Now, i'm not sure. It seems like both times that I have replaced the MAT sensor, it ran great for 5 miles or so then back to the same problem. I ohm'd the second MAT sensor after the no start. It ohm'd out at 18,500 ohms.
I'm at a loss at what to do from here. Maybe an ECU issue?
Any help would be greatly appreciated!
Shawn