tattuJay

Ive been reading posts since I bought my 93 runner about 4 months ago. when I bought it the air hose that connects to the throttle body was split and it wouldnt idle, it would just cut off if you took your foot off the gas. Replaced it with an after market hose. since then it idles but its never been steady. usually starting cold its around 1800rpms. then it can go anywhere from 1200-2000rpms after its warm. it will stay steady for awhile but eventually it will jump or drop. Anyway, last week end I went on a camping trip to the mountains. After about two hours of highway driving we got to the mountain and pulled off to make a drink . I left the truck running for about 20 mins. It was around 10 degress outside. It just cut off, wasnt really paying attention so not sure what happened, just know it cut off. I had to jump it to get it to start. Thought it was battery or alternator or something. Drove it to where we were gonna make camp, about a 1/2 mile of snow covered rough terrain, large rocks, steep hills etc. No problem. Once at camp, while unloading, I left the truck running to charge the battery just incase that was the issue (i understand the battery dying while it was running wouldnt normally cause it to shut off). I let it run for about 30-40 mins, it over heated and blew a hose where it attatches to the heater core switch(not sure of the proper term there, the part thats attatched to the firewall that opens and closes to allow water to the heater core). Had a piece of hose and while replacing noticed that where the hoses on either side of that heater core switch attach to it, the male sleeves on the switch were both cracked. So i bypassed the switch. topped the coolant off. Drove for about 20 minutes and lost my heat. Parked it for the weekend . Towed it home. Replaced thermostat with OE. flushed radiator, refilled, burped the best i could. Drove about 20 mins with heat working then i felt the heat temp drop enough to notice. Then it went back to normal. Then drop again, then back to normal. It seemed to raise (the heat temp from the vents) whenever I was on the gas then drop when I let off, but not every time. Temp gauge raised slightly a couple times but just a little, stayed close to the middle. After an hour and a half of driving I lost heat completely and temp gauge went to the red. Pulled over immediatley. I was close to the house by then so let it cool and when I started it, it would not idle. Had to keep foot on gas....babied it to the house. Let it sit over night. Started it next morning, idled at 2000 rpms. dropped to 1500 rpms after warm. heat was working but not nearly as hot as usual. drove about 20 mins and lost heat again, temp went to the beggining of red zone, just barely and then fluctuated slightly cooler and then back to barely redzone. Drove it home (about 10 minutes, through a couple lights and sitting still didnt change much except it didnt fluctuate to a little below redzone as it did while driving. As i was pulling in the drive way i lost idle again. I let the engine cool and it started same as it had after letting it sit over night, 2000rpms at idle then around 1500 after warm. Let it idle about 30 mins, temp gauge stayed dead center. Havent drove it again. I did notice that the fan on the moter side was blowing but the small fan on the bumper side of the radiator started blowing when I started it up but immediatley cut off and never blew again. Any idea whats going on? Before replacing thermostat I did compression check on radiator and cylinders, all good.

Austin Marr

I wonder if your heater core is clogged or not working properly? causing your coolant circulation to suck which would cause your heat to suck. also, at idle your not really "forcing" any coolant through the lines other than what your motor is running out so when your accelerating your forcing more coolant through the cooling system. you flushed your radiator and everything, now i'd check your heater core

motocrossaddict223

wow thats a lot of info. I had a similar problem, probably a year ago and it turned out to be my temperature sender and temperature switch. These are way back behind the intake against the firewall, a real pain with the plenum still on. Are you getting any codes? Do you know how to check for stored codes?

tattuJay

Ok, how do I go about flushing the heater core? The engine light came on once but went off shortly after. I dont know how to check codes on this truck, only familiar with obd 2. I know where to check the codes under the hood but no clue on how to go about it, and thanks for your responses guys.

tattuJay

and does the overheating have anything to do with the idle problem? Specifically with it not idleing?

Austin Marr

The heater core is a big pain in the rear. but do-able, research on here how to get her done. its not too bad, if your gonna dive into it let me know i may be able to offer some assistance, never flushed a heater core, i just replaced mine from a junkyard. I also think that your idle is in direct correlation with your water-temp sending unit. at high demands for coolant (for example, accelerating) it demands more coolant therefore pushing more coolant through the system. if its not getting enough coolant your idle may be higher because its trying to distribute more coolant because the sending unit is telling it to. DONT COUNT ME ON THAT but it would make sense to me that thats how the system would operate.

motocrossaddict223

I have no idea about the heater core, and in my case, my truck would not idle at all when my temp sensor and temp sender went out. my truck threw both codes at the same time so i cant be for sure which one it was specifically. As for checking your codes, i know the pin locations but i can't remember the terminal names. Im sure you can find it somewhere on here.

tattuJay

ok, thanks guys. Ill try first to read the codes, like I said no engine lights are on. What did you mean earlier when you mentioned stored codes? From there Ill flushh the heater core if I dont get any thing from the codes. Thanks guys and Ill keep you updated on the progress. I really appreciate your help.

Austin Marr

Ya man, i've been helped out a ton on here so i enjoy helping when i can. Once again the heater core is pretty cut and dry jut a bunch of dash pieces and like 4 bolts holding the cores housing. oh and then fighting the hoses to come off the core is a bugger too especially when your laying on your side under the dash

motocrossaddict223

The stored codes are ones that stay on your computer, but dont come up. It is likely that the one that you said came up but went away, got stored on your ecu, so when you check your codes it should come up.