[deep-six]

Hi All

I have an ongoing problem with idle speed fluctuation which is linked to coolant temperature (I think) (Vehicle is an 89 1.6 Carb Vitara)
When I start up cold it revs at about 1500 rpm til it warms up, but since I fitted a new thermostat and radiator a couple of years ago the temp climbs up to 3/4 hot before the thermostat cracks and lets coolant through the loop.
At this point the temp goes back down to about 1/4 and idle is at about 900rpm. This is all fine but in colder weather the thermostat closes, idle goes back up, temp rises to 3/4, idle goes down to about 200 RPM, engine shudders and threatens to stall, a few blips of the throttle needed to keep it running.
I have been putting up with this for the past few years, I think it is just a dud thermostat but I'm too lazy to pull it out and replace it UNTIL.........
Last week the radiator sprung a leak from the top tank. I figure this is from the constant heat cycle and pressure build up from the dud thermostat. I curse myself for not replacing the thermostat long ago.
It just cost me a new radiator I figure.
Fast forward to present day. New radiator fitted, system flushed, just fitted the new thermostat and topped up the water with engine running. I can hear the revs coming down as the engine heats up. Its doing what it is supposed to be doing so I'm reasonably happy, but the temp keeps climbing, the revs drop and the thermostat has not cracked yet. I can tell this as I'm watching for water rushing through the top tank. plus the top tank is cold along with the top hose. Engine stumbles and threatens to die and its Deja Vu. I cant understand why this is happening. I'm normally pretty calm and collected but this is getting ridiculous. I feel like kicking the grill and yelling out obscenities but there are children nearby and I don’t want to startle them, or break my grill for that matter
Has anyone had this problem and can offer a fix.
Thanks for reading and hoping for an answer

[Jeff1400]

The factory service manual has a good description of how the auto choke should work.
I would be checking that. Lift off the air filter and watch the choke butterfly.
It should be closed when completely cold. It should crack slightly on startup. (From vacuum acting on one part of the choke opener)
Then as temp rises it should open gradually. Until at running temp it should be wide open.
If not it could be the wax element (which is what makes it open gradually) not working?

It's worth a shot.

If it is that I have no idea where to source one. I got quoted about $600 to service mine with parts. If they could get them.

[DarkHorse]

What thermostat have you been using? The cheap generic ones are prone to failure on install. It's one of thoe things that's worth forking out for genuine IMO.

[deep-six]

Thanks guys, its not so much the idle that bothers me, although it is annoying, its the temp rising to 3/4 hot that really worries me. Oh, and the choke flap is fully closed at cold
It kind of settled down a bit after a few days driving, the temp still varies from full cold to almost Fukashima. then drops again.
I don't know what the answer is. I do know how to bodge it up by just taking the thermostat out altogether and winding the cold idle back down to around 800 rpm. Its not the right way to fix it but its so damn annoying as it is.
Its a shame as it is such a good unit other than that. Always starts up with just a click of the starter. A bit annoying really when you just want to bump the motor over a few degrees to tighten up the fan and it jumps to life and scatters your socket set off the air cleaner, but thats another story.
Anyway, as always, I appreciate any input.

Cheers

[Mike_B]

Might also be worth checking the wiring on the temp gauge, and check coolant temp with an alternative temp measuring device to be sure the temp variations you seeing are correct, apart from that the auto choke operation (or not) as noted above, (cos apparently the efi Vits with wax pellets in the throttle body can have issues with running up from a cold start in low ambient temps when they get older). What temp rating is the thermostat that is in it? Might be better with one that opens at a different temp?