Terrano no water circulation

[chw2]

I just bought a Terrrano 1994 V6 VG303 Automatic in very good condition. The viscous Fan coupling was lock on when I got it and truck was using lots of fuel. I believe the car was running cold so I took it to the shop. I had replaced the Timing belt, tensioner, waterpump, radiator, viscous fan coupling, new coolant, Car has done 158,000 Kms. Still the car runs could, IE the choke is half on most of the time RPM at 1,000 I get 3 Kms/l of gas - crap. I checked ECU codes. After driving for 20 minutes idle drops to 750 RPM. If stop for more than 1 minute choke comes on again next start. car runs well otherwise no missing, heater is hot and I can't see and mods to the water system.

ECU: Mode 1 when first turn on both lights are off. RPM to 2000 and the green light comes on and stays on for 18s and then off for 3s and then on for 18s repeating. Mode 3 code 55 everything is OK.
** WHAT does this mean as not in book.

CODE 2 Mixture ration book says if RED and Green blink simultaneously. Mine at 2000 RPM both come on and stay on. No blinking.
** WHAT does this mean as not in book.

Plugs are all black with burnt carbon (none are oily, or tan) Distributor: Both rotor and HT lugs had corrosion (Have just cleaned up for now but will need all 3 replaced.

Have disconnected heater - no difference, restricted top radiator hose to 20% flow - no difference. Can't see any water moving in radiator after driving for 30 mins in 15 degrees c - water at 30 degrees c in radiator and temp gauge at 1/4. It appears I've got an air cooled terrano

Please help, any suggestions.
1) Can the ECU cause this
2) My past tells me that only the Stat can do it. Mine is not opening as the water does not get hot enough. I removed heater hose after a long drive, it was hot but did't burn me.

[Slumpert]

You did not mention replacing the thermostat. Typically the weep holes in it would still allow enough coolant flow to warm up the radiator hose but it is possible it is clogged up really good.

[chw2]

Thank you for your reply. Yes I also had the thermostat replaced with waterpump. A repco one not Nissan though I believe. The garage assures me they checked it prior to going in. I'd expect if it was stuck open I'd see water moving on top of radiator (is that correct) and closed I should overheat, the water just rises and falls when I rev the engine and only gets to 30 (ish) degrees c - checked with Radiator cap off so no water pressure.

[Slumpert]

If your seing it rise and fall with engine speed then you might still have large air pocket. Fully filled there is no way to compress the coolant to cause a fluid level change.

[chw2]

Thanks I'll try to burp again - When hot top radiator hose is really firm so I thought the rise was coming from top hose.

Burping - Start engine when cold, turn heater on full, remove radiator cap and run until engine is warm - look for bubbles. Any other tricks.

[chw2]

I parked on a hill front up, cold, heater on radiator cap off. Ran it for about 30 mins water over flowed from radiator, a few small bubbles. Held on 1000 RPM for a few minutes that let a couple of bigger bubbles out. Now on rev the water doesn't rise and fall (much). On rev up the water moves to right in radiator, on rev down moves to the left - not fast but looks to move. No change to temp gauge but idle is really nice. Finger test on water through radiator cap is around 40 degrees, hot but bearable. I'll try to burp again once it cools down again.

[Slumpert]

Sounds like you got it. Yes those engines barely need the radiator it seems for light duty.

Very possible the previous owner did a bypass for the upper intake. That would certainly affect the choke.

[chw2]

Thanks Slumpert, burped another couple of times but no large bubbles this time so I think we got it. Now the choke comes off after a few minutes. Wicked. Doing a mileage check. I had burped the truck many times prior but not on the 60% angle I had it on the last few times. Thanks again.