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Rough running or low idle speed when air conditioner is operating.
The air conditioner (a/c) takes a fair bit of horsepower from the engine. A Fast Idle Control (FICD) solenoid allows vacuum pressure to operate an actuator (FIA) that increases the idle speed of the engine to compensate when the a/c kicks in.
There is a small rubber vacuum hose from the inlet manifold to the FICD (first picture) which is mounted above the brake booster. The FICD is supplied 12 volts via an Orange wire with a blue or purple stripe. Its negative is a black wire.
Another hose runs from the FICD to the FIA diaphragm (second picture) which is mounted near the front of the carby. Check the hose for splits or holes if the engine runs rough when the a/c cuts in.
When the a/c cuts in you should be able to see the FIA rod push on the carby linkage. If it doen't operate, you may need to use a hand vacuum pump to check that the diaphragm rubber isn't split or holed.
Another possibility is that the FIA operates, and the revs will rise, but the engine runs rough. If this happens the diaphragm rubber may have a small hole or split. This will become apparent when you use the vacuum pump and the actuator operates but returns to its normal position while it is still connected.
The FICD is powered by the air conditioner relay on a vehicle with a manual transmission.
A vehicle with an automatic transmission also has additional protection control via a Thermo Switch which operates an a/c cut relay, connected in series with the a/c relay.
Cooling for an automatic transmission is achieved by pumping its fluid through a core inside the radiator.
The Thermo Switch is situated on the radiator and it should have a blue and Yellow/blue wire. It operates when the engine coolant reaches 107 degrees C to cut out the a/c and off to allow the a/c to operate when the temp drops below 103 degrees C.
Last edited by mudnut; 15th February 2015 at 01:41 PM.
Draining coolant from the RB30 radiator without splashing it everywhere is a tricky and tedious job at the best of times.
Undo the radiator cap, so there is no negative pressure applied to the system as the coolant level drops.
I have made a simple device from an empty silicon tube, that catches the coolant before it dribbles onto the chassis and drips onto the floor at various locations.
Unfortunately when the drain plug in the block is undone, the coolant goes everywhere, so it is best to leave it until the radiator is drained to reduce the flow.
This is the RB30 transfer case shift instruction sticker which is supposed to be attached to the back of the Driver's sun visor. The owners manual also has the instructions.
This is the Air Intake Pre-heat assembly fitted to a stock RB30S.
When the engine is cold, vacuum is applied to the diaphragm inside the silver unit on top of the air intake.
This unit has a small arm which operates a flap that closes the normal air intake and opens the "Stove Pipe".
The Stove pipe is attached to the metal shroud which collects hot air from around the exhaust manifold.
Vacuum pressure to the diaphragm is halted as the engine heats up, so the flap closes the stove pipe and opens the normal air intake.
The Pre-heat system must be operational for the vehicle to pass a roadworthy.
To prevent the pre-heat flap from opening during a trip where I am likely to encounter water crossings or dusty conditions, I take the normal hose off and stop up the holes with the two plugged pieces. (2nd picture).
Another simple way to block the hose is with an appropriately sized ball bearing.
As I live in a cooler climate, and have had to remove the heater grid positioned at the base of the carby (It had started to disintegrate and pieces were falling into the engine) For normal driving I keep the pre-heat system operational as it helps the engine warm up quickly to normal running temperature.
So this is an RB30S or a converted RB30efi unit. Have you changed your diff ratios, as pushing 35' tyres will use a heap of fuel.
Sorry for the delayed response mate, only just saw this.
RB30S, running original diff ratio's (pretty sure they are 4.3 from factory). Recent trip around Tassie, did a tad over 3000kms, a lot of low range/sand stuff, windy coastal roads and dirt roads in that. Fully loaded with all our camping gear, me and the missus, we averaged around 18.8L/100km. I was pretty happy with that as we really didn't spend much time on the highway.
That was about my average for the Beachport / Robe trip. So you've done well. Since I've had the carby kit fitted and the engine dyno tuned I can see that the RB30 wouldn't struggle pushing the larger tyres as I thought it might have.
Last edited by mudnut; 15th February 2015 at 01:45 PM.
That was about my average for the Beachport / Robe trip. So you've done well. Since I've had the carby kit fitted and the engine dyno tuned I can see that the RB30 wouldn't struggle pushing the larger tyres as I thought it might have.
Yeah just took a bit of getting used to how to drive it. With the 35's, I don't use 5th too often anymore, unless I've got some nice flats, but other than that, she'll sit on 110kph all day. Longer hills tend to find me winding back to 3rd but I've gotten used to it not being a supercar haha.
Best fuel economy figures since I bought the Old Trol and have fitted a winch and 2inch lift at 14.91 litres per 100 km with 90% highway driving using unleaded. Very happy with that considering the weight and "super efficient aerodynamics" of the GQ.
Last edited by mudnut; 15th March 2015 at 08:54 PM.
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Originally Posted by mudnut
