myjeepisDEAD
NAXJA Forum User
- Location
- Chicago, IL
My girlfriend drives a 1999 Cherokee (4.0L, manual trans) and it died when we were off-roading. We checked fuel and air - both fine. We narrowed it down to spark - there was none. No spark at the plugs and no spark from the coil (using spark tester).
Checked fuses - all good.
Swapped relays - all good.
Did a quick check of the wires - all seemed fine, nothing ripped, braised, or out of the ordinary.
Pulled off the distributor cap. There was a bit of moisture in there (and corrosion). We let it dry and reassembled it.
Turns out the Crankshaft Position Sensor was bad (really common). This one was actually destroyed (melted, torn up and ugly - really uncommon?). We replaced it. Still no spark from the coil.
Replaced the coil. Still no spark. Tested voltage to coil - good.
Towed the Jeep to Advance, Autozone, and a mechanic. They all narrowed it down to the ECM. Bought a new one, flashed it, and swapped it in. After that we got a weird, intermittent spark from the coil.
Swapped the old ECM back in just to see if that was actually the problem. We got the same weird, intermittent spark from the coil - must have been testing wrong before? Guess the old ECM is good, but still testing everything with the new one.
When trying to start, the car cranks fine, sounds good, but the coil sends a spark every 3-5 seconds. I'm no expert, but it seems like it should be much more often - like every second or so. I'm not sure about the strength of the spark, but it was strong enough to be extremely unpleasant going through my hand.
Thought maybe the new CPS was faulty, so replaced it again. Same intermittent spark.
Also replaced the coil again. Same intermittent spark. Thank goodness Advance has such a great return policy!
Replaced distributor cap and rotor.
Replaced pickup coil underneath the cap.
Another thought: I heard about a freak accident about another Cherokee that was not getting a spark, and it turned out to be an O2 sensor after testing or replacing just about everything else. It doesn't seem like this would make sense at all, but I guess the sensor was sending a faulty code (or short) that prevented ignition. On our Cherokee, part of the exhaust actually fell off RIGHT after the rear O2 sensor on our Cherokee, and I'm 99% sure the sensor got wet when we went through water. I unplugged both sensors and still got the same intermittent spark.
Any ideas? All help is very very very much appreciated. This beast has been out of commission for 3-4 weeks now!
Checked fuses - all good.
Swapped relays - all good.
Did a quick check of the wires - all seemed fine, nothing ripped, braised, or out of the ordinary.
Pulled off the distributor cap. There was a bit of moisture in there (and corrosion). We let it dry and reassembled it.
Turns out the Crankshaft Position Sensor was bad (really common). This one was actually destroyed (melted, torn up and ugly - really uncommon?). We replaced it. Still no spark from the coil.
Replaced the coil. Still no spark. Tested voltage to coil - good.
Towed the Jeep to Advance, Autozone, and a mechanic. They all narrowed it down to the ECM. Bought a new one, flashed it, and swapped it in. After that we got a weird, intermittent spark from the coil.
Swapped the old ECM back in just to see if that was actually the problem. We got the same weird, intermittent spark from the coil - must have been testing wrong before? Guess the old ECM is good, but still testing everything with the new one.
When trying to start, the car cranks fine, sounds good, but the coil sends a spark every 3-5 seconds. I'm no expert, but it seems like it should be much more often - like every second or so. I'm not sure about the strength of the spark, but it was strong enough to be extremely unpleasant going through my hand.
Thought maybe the new CPS was faulty, so replaced it again. Same intermittent spark.
Also replaced the coil again. Same intermittent spark. Thank goodness Advance has such a great return policy!
Replaced distributor cap and rotor.
Replaced pickup coil underneath the cap.
Another thought: I heard about a freak accident about another Cherokee that was not getting a spark, and it turned out to be an O2 sensor after testing or replacing just about everything else. It doesn't seem like this would make sense at all, but I guess the sensor was sending a faulty code (or short) that prevented ignition. On our Cherokee, part of the exhaust actually fell off RIGHT after the rear O2 sensor on our Cherokee, and I'm 99% sure the sensor got wet when we went through water. I unplugged both sensors and still got the same intermittent spark.
Any ideas? All help is very very very much appreciated. This beast has been out of commission for 3-4 weeks now!