coolguy2424
NAXJA Forum User
1988 Jeep Cherokee XJ Limited, 4.0L, L6, automatic, selectrac. It has the 5,000 lb towing package, so I'm not sure if it has a 180 or a 195 tstat. When someone takes off the housing is there a way to tell?
The Jeep temperature gauge has always run halfway between the second line, and 210, I guestimate at about 180-185, maybe 190. And I have had this Jeep since 1993. I got it five years old with 75,000 miles on it, and it now has 175,000 miles on it. I have never changed the thermostat to my recollection, in 31 years, and rather doubt it was changed in the first five years right?
( https://www.cherokeeforum.com/f2/thermostat-temp-suggestions-214149/index2/#post3143595 "They also made a 180* extreme duty(towing) thermostat")
( https://www.cherokeeforum.com/f2/best-thermostat-very-very-hot-climate-253837/#post3576294 "180 is the minimum you should go, some XJs with the tow package came with one from the factory")
When I start the engine, and get right on the freeway, the temperature climbs over several minutes until it reaches about 180, then quickly drops down to 155-160, the second line on the temperature gauge. I presume that's the thermostat opening. It then stays running cold, and rich, and when I smog tested, it had high CO, but the smog guy thought it was the Map sensor he thought it was a "fuel control problem" as the CO seemed to be oscillating "car thinks it's under load." I tested the Map sensor and got 4.8 with key on engine off, and 1.8 with engine on, and as I revved the engine this sweeped down to 1.3 or even lower, so I figured it was okay.
A month earlier I had smoged it and gotten high NOx, and low CO, and looked under the vehicle and saw big holes in the front exhaust pipe with hot air coming out. I had another mechanic replace the front exhaust pipe a month later, and the next day went to smog again, and this. I don't remember if it was running cold during the month before I replaced the exhaust pipe, I actually only noticed that after the second smog. I subsequently replaced the Oxygen sensor, and tested the coolant temperature sensor, (and replaced the knock sensor as it was broken). And I tested the TPS sensor and found it good too.
So I was wondering if it is likely the thermostat, and if so, I presume I should stick with the 180, or if this could be caused by a cracked exhaust manifold, which connects to the front exhaust pipe, right where they replaced it, and the new oxygen sensor sits right at the end of the exhaust manifold, right before the pipe connection. When I suggested this to the smog guy, he seemed to think this was unlikely, and started talking about in that case, the vehicle has some sort of restriction or something blah blah you wouldn't see smog results like this.
The thing is, the thermostat can't be stuck open, as the car's temperature repeatedly goes up to 180 from cold, and then immediately falls down to 155-160, as the thermostat presumably opens. Could it still be broken though?
Synopsis:
When I start the engine, and get on the freeway, the temperature climbs until it reaches 180, then quickly drops down to 155-160. Stays running cold at this temperature after that. Won't pass smog as has high CO (and high HC, and low NOx). Should I change the thermostat, or before I do this, can you think of anything other cause of this??
I also unplugged the battery for five minutes to clear the ECU after I:
Changed Oxygen Sensor & Knock Sensor, and cause of the new pipe, and,
Checked Map Sensor and TPS Sensor, and Coolant Temperature Sensor
Can the thermostat be broken, and still open and close some? Or is there something else I could check first? Doing unnecessary work is annoying.
Would buying the Red Brick MT2500 to hook up tell me anything? NickInTimeFilms basically shows you everything it could show me, from 7:25-12:52: www.youtube.com/watch?v=qPV5pEGUHWw&t=445s Do I need this?
The Jeep temperature gauge has always run halfway between the second line, and 210, I guestimate at about 180-185, maybe 190. And I have had this Jeep since 1993. I got it five years old with 75,000 miles on it, and it now has 175,000 miles on it. I have never changed the thermostat to my recollection, in 31 years, and rather doubt it was changed in the first five years right?
( https://www.cherokeeforum.com/f2/thermostat-temp-suggestions-214149/index2/#post3143595 "They also made a 180* extreme duty(towing) thermostat")
( https://www.cherokeeforum.com/f2/best-thermostat-very-very-hot-climate-253837/#post3576294 "180 is the minimum you should go, some XJs with the tow package came with one from the factory")
When I start the engine, and get right on the freeway, the temperature climbs over several minutes until it reaches about 180, then quickly drops down to 155-160, the second line on the temperature gauge. I presume that's the thermostat opening. It then stays running cold, and rich, and when I smog tested, it had high CO, but the smog guy thought it was the Map sensor he thought it was a "fuel control problem" as the CO seemed to be oscillating "car thinks it's under load." I tested the Map sensor and got 4.8 with key on engine off, and 1.8 with engine on, and as I revved the engine this sweeped down to 1.3 or even lower, so I figured it was okay.
A month earlier I had smoged it and gotten high NOx, and low CO, and looked under the vehicle and saw big holes in the front exhaust pipe with hot air coming out. I had another mechanic replace the front exhaust pipe a month later, and the next day went to smog again, and this. I don't remember if it was running cold during the month before I replaced the exhaust pipe, I actually only noticed that after the second smog. I subsequently replaced the Oxygen sensor, and tested the coolant temperature sensor, (and replaced the knock sensor as it was broken). And I tested the TPS sensor and found it good too.
So I was wondering if it is likely the thermostat, and if so, I presume I should stick with the 180, or if this could be caused by a cracked exhaust manifold, which connects to the front exhaust pipe, right where they replaced it, and the new oxygen sensor sits right at the end of the exhaust manifold, right before the pipe connection. When I suggested this to the smog guy, he seemed to think this was unlikely, and started talking about in that case, the vehicle has some sort of restriction or something blah blah you wouldn't see smog results like this.
The thing is, the thermostat can't be stuck open, as the car's temperature repeatedly goes up to 180 from cold, and then immediately falls down to 155-160, as the thermostat presumably opens. Could it still be broken though?
Synopsis:
When I start the engine, and get on the freeway, the temperature climbs until it reaches 180, then quickly drops down to 155-160. Stays running cold at this temperature after that. Won't pass smog as has high CO (and high HC, and low NOx). Should I change the thermostat, or before I do this, can you think of anything other cause of this??
I also unplugged the battery for five minutes to clear the ECU after I:
Changed Oxygen Sensor & Knock Sensor, and cause of the new pipe, and,
Checked Map Sensor and TPS Sensor, and Coolant Temperature Sensor
Can the thermostat be broken, and still open and close some? Or is there something else I could check first? Doing unnecessary work is annoying.
Would buying the Red Brick MT2500 to hook up tell me anything? NickInTimeFilms basically shows you everything it could show me, from 7:25-12:52: www.youtube.com/watch?v=qPV5pEGUHWw&t=445s Do I need this?
