ShawnT

I found the problem, two bare wires behind the TBI. It appears the wires were rubbing through on the intake manifold and shorting out. Luckily I had my head in the engine compartment as my wife was cranking the engine over. I saw an orange glow, which led me to investigate further. It appeared someone had repaired the wire before and did a poor job, leading to a poor routing angle. I replaced the bad section of wire, inspected the rest of the wires in the connector that plugs into the TBI and rerouted it. On a side note: Does anyone have a good solution to sealing the plastic valve covers? When I purchased this Jeep, the previous owner said he had just replaced the valve cover gasket with a OEM O-ring style gasket that fits inside of a channel that is grooved into the valve cover. It was leaking pretty severely. I replaced the valve cover gasket again with a Fel-Pro rubber flat style gasket, using a thin layer of Permatex (for added insurance) with the same, oil leaking result. I was meticulous in cleaning the head surface and the valve cover, as well as inspecting it for any cracks or anomalies. I'm hoping someone has some experience with these plastic valve covers.

So another weird question. Each time I have replaced the MAT sensor, the engine started right up and ran seemingly normal for approximately 5-7 miles and then died. Since I installed a Car Quest aftermarket part, do you that its getting ruined quickly because of a different issue? or possibly the wrong sensor? Doesn't make sense to me.

Ok, I checked the engine compression before I saw this response. I found cylinders #1, #2, #4 to be 120 PSI. Cylinder #3 was 130 PSI. I haven't performed a leak down test yet. I also checked the fuel return line from the TBI to the tank by removing the fuel tank filler cap and inserting compressed air at a decent rate from TBI side, using an air hose. My son was on the fuel tank end stating he could easily hear the flow of air. I know, not super scientific, but seemed to work.

I forgot to add that into my trouble shooting description. I changed the spark plugs with Champion plugs. I also checked the fuel pressure at the main fuel line coming into the TBI, which read approximately 50 psi. I then tested the fuel pressure at the TBI test port which read 14-15. I will go check compression on all four cylinders and report back. Thanks for the quick response! Shawn

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