Odd erratic engine temps

[fixkick]

Hi All-  1996 X90 1.6 G16b 4wd manual, complete rebuild.

  I've gotten most of the kinks worked out of this long project but I'm baffled by a varying temp condition I cannot solve.  Everything on this engine is new.  totally rebuilt engine, all new hoses, new waterpump, radiator, egr valve, 180thermostat..  practically everything new, I've flushed and refilled the coolant system twice now just to be safe, burped the coolant system 4/5 times now.  Additionally I have an array of extra gauges (water and oil temp, oil pressure, fuel pressure, etc) which is making it easier to watch whats happening.  I'd prefer this not turn into a debate about the quality of aftermarket gauges because I've carried an IRHeat gun with me for the duration of this experience to verify the readings are accurate and I'm not just going crazy (though that is debatable). Here's my experience:

Summer conditions in the US midwest, (60-80degrees outdoor temp)

Cold start, idle, water temp comes up to 200ish before the thermostat opens, upon opening WaterTemp drops back to 175ish, then reclimbs back to 195-200 and remains there.  (I'm on my 3rd thermostat after assuming maybe I just got a dud, symptoms havent changed)

Under these startup idle conditions OilTemp stays right around 140ish
Oil Pressure is always good through all of this. 

I live in a rural area so I drive a consistent 55-60 mph most everywhere.

When I get out on the road the water temp will vacillate with no correlation to speed or strain; WaterTemp will climb sometimes as high as 210 but never over, gently sliding back and forth generally between 190ish-205ish.  The oil temp will rise and fall (slowly) as well between 140-180, doesn't matter if I'm cruising or hard on the gas, no variation of load condition or throttle seems to directly affect the temps, and the Water/Oil temps do not vary collectively.  I took a day road trip (500 miles round trip) and monitored things closely for the duration of the drive.. both the water and oil temp will rise and fall with seemingly no explanation, and no relation.  I have no dash so I can easily point the IRheat gun into the heater core while driving and see a very accurate watertemp of whats coming directly out of the head, and it matches that gauge pretty much exactly throughout all of the variation.  I'd give more examples but its literally endless variability; For a while it'll run water195ish oil 150ish, then for no reason water temp will slowly climb or fall within the 190-210 range and pick a new position to operate at until inexplicably it changes again.  Same with the oil temp in the 140-180 range, again with no relation to each others temperatures.

When I come to a stop (idle) either at a light or when my travels conclude the variations continue.  Sometimes all the readings remain exactly as they were driving, sometimes water temp drops back to 180ish sometimes it climbs to 210ish or anywhere in between, Oiltemp the same with no correlation, and I mean absolutely no relation.  Ive had the water temp drop down to 180 at idle and the oil temp summit to 180, I've had the water temp climb to 210 and the oil temp stay or decline to 140ish.

I'm completely baffled.  

Only 1 condition made what seemed to be an obvious impact on the running temperature.  During my day road trip I encountered a small thunderstorm, outside air temp dropped probably 25 degrees very quickly, and pouring rain.  Upon entering that weather event everything dropped to what I would expect to be normal operating temps based on all information (and my experiences) watertemp went to a stable 180, oiltemp to 140.  My journey ended amidst the storm so I wasnt able to see what the results might have been exiting those specific conditions.  That event lead me to think maybe there was a blockage in the radiator..  but the radiator is less that 4 months old, and I've pulled it out completely and flushed it twice (before this day trip).

So again- completely baffled.  

Here are a few other occasional symptoms I get with the vehicle, which Ive attempted to address and remedy via all the processes I can find here and elsewhere with no luck.  though they may be completely unrelated I feel the are worth mentioning in case they are potentially applicable to the scenario.  

Slightly elevated idle (900ish) always.  


Both of these happen inconsistently, unpredictably and not often:

Cold start sputter and die.  when it happens its only once, when I restart it stabilizes and idles reliably.  This has happened less than a handful of times, and only after not driving the vehicle for more than a few days.

Random P0400 code.  I leave my OBD2 reader plugged in most of the time, and 1 in maybe every 7 trips I'll get a P0400.  (similar driving condition trips)

thats all I've got for now..  let me know if more info could lead to better insight.  I'm totally lost, and concerned about running the vehicle regularly with these varying temp conditions even though none of them indicate extreme issues.  

I appreciate any insight anyone might have!!!  Thank you!!!

I ran 195F thermostats in all 3 of my Sidekicks (92/96/97)

I ran 195F thermostats in all 3 of my Sidekicks (92/96/97)
no statement at all what gauges you have make or brand and worse now connected exactly.
The engine shows no signs of overheating at all:
stream flying out. engine pinging, power lost,  and misfiring...from pinging. 
water overflow side tank plastic not shooting cap off and green coollant every where,
are you running 50% coolant ratio for sure?
no dash,= no cluster? , no way to see stock gauge, ok, no big deal that.


so it all gets down to the 2 gauges, and nobody hear can guess that,  impossible ......

lets forget oil temps for now that is 100% related to how the sensor for the gauge was fitting, and maker of gauge. and model. but lets do 1 thing engine coolant temps.
900 rpm (obd2?) is too high and the startup is failing my guess due to ISC or IAC stuck, 
p400s is EGR, and the mono port is packed incarb (and lots more)

200 is NOT HOT, ok? you do know all new cars are 200f by EPA edict right?  its not HOT infact the radiator can expel more HEAT at that time for sure outside temps at 120f like here.

The max heat will be flogging engine up hill , hot.  max heat out of the radiator if the temps are ok moving fast. but never good at a red stop sign,  then the silly old fan clutch is bad.
or its belt slips.


your car is not stock so any help need you telling in great details all thing not stock and what was changed and how done exactly.
the best aftermarket coolant temps are obtained from removing the stock 1 wire sensor for the old guage.
the 2nd best is the inline sensor in a hose adapter,  its pipe that has 90degree side sensor.  and you cut say the heater hose and fit there.

many that suck are the thermal sensor that slides under any hose clamp.
my gosh I have seen like 10s types in 55 years,  some good some bad and IDK what you have.

the top rule for being a tech, is never trust your readings.  (measurement errors are fact of life and not your fault) double check your work,  
you  have like 3 sensors there now.
1: ECT on PCM  OBD2 coolant temp is this telling lies.?
2: the unstated gauge. nor sensor type and  the way deployed.
3: IR GUN to heater core side tank , what do the 3 tell you.?  the core HAS 2 TANKS ONE HOT ONE COOL.   yes water exits hot head rear to this one tank.


now quality debate is possible ever, due to no gauges told.  if lucky most consumer cheap gauges are 20% accurate and the stock gauge has no NUMBERS ON IT (no nnnF)
VDO and SW make some top grade gauges, what do you think F1/NASCAR Race cars run , EBAY gauges,? sure  no.

like this pro-comp set, mounted NASCAR funny like so driver at 200mph does not have to read ahhh 180f, only that needles are in the HORZ position,  cool no::????