1041510
This problem began on the first test drive I took after installing a new longblock in my 1988 Cherokee Chief. At between 1200-1800 rpms under a load (gradually accelerating from a stop or driving uphill), the engine would continuously miss. The tach would drop sharply then immediately recover, like there was a momentary interruption in spark. If I gave it lots of gas and accelerated quickly, it ran great. The old engine had 182k on it and had lost all oil pressure. It sat in a barn for almost two years until late this May. I replaced the distributor cap, rotor, pick-up, plugs, wires, throttle positioning sensor, O2 sensor, coil, module, fuel pump and filter, and the computer until I finally succumbed to defeat and took it to a dealer. They told me the computer (that I had bought from a parts store) and EGR valve were bad. I had them replace the parts, and other than a constant overheating battle we still wage, she ran like a champ....for about 5000 miles. (I have recently installed a 3 row GDI radiator, but on the steep roads I often drive it still runs hot, and if a hi-flow thermostat housing doesn't work, I will convert to the open cooling system).
A couple of weeks ago the same problem began occuring; an occasional miss at low rpms. It only happened once or twice each time it occured, then it would straighten out. Last week, it suddenly started dying while idling at traffic lights, and if it was warm, it was nearly impossible to start. I took it to a different dealer (I had moved to Utah), and they told me the vac line going to the EGR valve was split. Also, the top of the plastic reservoir had a crack that spewed coolant onto the coil and distributor when it was hot. They fixed these problems as well as replacing my fuel pump and sending unit (long story short- my tank leaked because I screwed up my sending unit installing an aftermarket pump). The dealer told me my overheating problems should be fixed because my cooling system was now under pressure. I picked it up from the dealer on Friday. The jeep ran perfect for 500 miles, but while driving on a washboard road in the Uinta Mountains this weekend, it started missing again at low rpms; I had to keep it above 2000 rpms to keep it running regularly. When I got off the washboard and onto pavement, it still missed for about a minute before it straightened out. While driving on a long, steep section of highway (5-7% grade), it seriously started missing in the 1600-2200 rpm range. I had to slow to 55 mph and take it out of overdrive keeping it above 2200 rpm. On the way down that pass and then going over the next pass (which was less steep) it only missed a few times, and otherwise ran great. I have never replaced the CPS. I am beginning to think I might have a short somewhere. If this is the case, where and how should I look? Both Jeep dealers did a diagnostic check. It still ran hot this weekend (210-220 on the highway). I am going out of my mind! [addsig]
This problem began on the first test drive I took after installing a new longblock in my 1988 Cherokee Chief. At between 1200-1800 rpms under a load (gradually accelerating from a stop or driving uphill), the engine would continuously miss. The tach would drop sharply then immediately recover, like there was a momentary interruption in spark. If I gave it lots of gas and accelerated quickly, it ran great. The old engine had 182k on it and had lost all oil pressure. It sat in a barn for almost two years until late this May. I replaced the distributor cap, rotor, pick-up, plugs, wires, throttle positioning sensor, O2 sensor, coil, module, fuel pump and filter, and the computer until I finally succumbed to defeat and took it to a dealer. They told me the computer (that I had bought from a parts store) and EGR valve were bad. I had them replace the parts, and other than a constant overheating battle we still wage, she ran like a champ....for about 5000 miles. (I have recently installed a 3 row GDI radiator, but on the steep roads I often drive it still runs hot, and if a hi-flow thermostat housing doesn't work, I will convert to the open cooling system).
A couple of weeks ago the same problem began occuring; an occasional miss at low rpms. It only happened once or twice each time it occured, then it would straighten out. Last week, it suddenly started dying while idling at traffic lights, and if it was warm, it was nearly impossible to start. I took it to a different dealer (I had moved to Utah), and they told me the vac line going to the EGR valve was split. Also, the top of the plastic reservoir had a crack that spewed coolant onto the coil and distributor when it was hot. They fixed these problems as well as replacing my fuel pump and sending unit (long story short- my tank leaked because I screwed up my sending unit installing an aftermarket pump). The dealer told me my overheating problems should be fixed because my cooling system was now under pressure. I picked it up from the dealer on Friday. The jeep ran perfect for 500 miles, but while driving on a washboard road in the Uinta Mountains this weekend, it started missing again at low rpms; I had to keep it above 2000 rpms to keep it running regularly. When I got off the washboard and onto pavement, it still missed for about a minute before it straightened out. While driving on a long, steep section of highway (5-7% grade), it seriously started missing in the 1600-2200 rpm range. I had to slow to 55 mph and take it out of overdrive keeping it above 2200 rpm. On the way down that pass and then going over the next pass (which was less steep) it only missed a few times, and otherwise ran great. I have never replaced the CPS. I am beginning to think I might have a short somewhere. If this is the case, where and how should I look? Both Jeep dealers did a diagnostic check. It still ran hot this weekend (210-220 on the highway). I am going out of my mind! [addsig]
