what is going on?

[silviagod]

Can anyone offer advice please.
My Silvia is misbehaving, it drives well but is damned uneven on idle. I have tried different fuel pumps, distributors, fuel pressure regulators, air-flow sensors, ECU's and the damn thing still does the same. It is perfect from cold until it warms up and in order to keep the damn thing running I am up to 2.5 bar on the fuel pressure. If I allow more air to get in it runs rich as hell because I forgot to put the dump valve back on and it ran perfect but very fast. I also tried blocking off the dump valve to eliminate it from the equation. I suspected No." injector at one time and replaced it to no effect and the spark plugs are new. If I unplug the air-flow sensor it runs slightly rich and idles perfect. I tested the wiring from the air-flow sensor to the ECU and that is ok, the water temp sensor is working fine and I have a healthy spark. I first became aware of the problem when the temperature took a dive and we had a sharp frost and the ECU codes are showing no faults.

Please please please can you offer any suggestions where to look next? The only thing I haven't checked are the valve clearances and a dry compression test on a warm engine is giving 150psi on all cylinders.

[umpkin]

how good is the turbo??? when my hybrid wore, it had a mass of in/out play, but on idle it was tight and stopped spinning, this made it idle very lumpy.

once i got the new tubby, it was all fine.

[silviagod]

Thanks for the reply, that is about the only thing I haven't checked. I will have a feel of my shaft tomorrow and see what it feels like. The turbo spools up well though, I get good dumps and the car doesn't use any oil. Also there is no water in the oil or oil in the water.

[adzs12]

Originally Posted by silviagod

I will have a feel of my shaft tomorrow and see what it feels like. .

All jokes aside my car is misbehaving since the cold weather aswell, my temp gauge is wondering and the heater blows hot when it wants too so i think its new thermostat time. Also though its been making extreme boiling noises when at idle and its hesitated a few times on boost, its as if its low on fuel when im boosting it which is causing it to act like a missfire. Just feels retarded. It steamed/smoked alot when slowing down and when i parked up so a compression test is in order aswell although no mayo is present in the oil cap and dipstick looks normal too. I know my turbo isnt great and has been on its way out for a while now so i dont suppose this is helping matters on boost.

[northerner]

Paul I have had to change my air choke idle thingy as it was *ucked! and wasn't working which gave a funny idle. Maybe its broke/not working properly. Also on the IAA thingy there is Two plungers which open when the idle goes low ie when the lights are on etc to let more air in. These gave me strange idle probs on my old Cherry Turbo. Undo them and clean them out! You've checked all the obvious so nows the time to step back and think of the Not so obvious!

[silviagod]

Thanks Steve but I have tried a different clean IAA unit and it made no difference and the auxiliary air valve is working fine because the tick-over is perfect until the car warms up.
ADZS, the thermostat is working fine and the temperature gauge goes to the middle as per workshop manual.

Hopefully a friend who has a MOT garage may be able to check the injectors on the car with an oscilloscope and tell me if one is acting the goat as the lumpyness is not every fourth time like a proper misfire.

[adzs12]

My gauge never goes past a 1/4 of the way up the gauge as my twin kenlo hurricanes dont allow it too , so i found it odd when it kept creeping up to half way. Il change the thermostat anyway as the cooling system could do with a flush out and fresh antifreeze before the frosts really set in. As for the slight hesitation on boost and it feeling retarded il have to see what i find.

[silviagod]

it is the thermostat that controls how far the needle goes not how big the fan is. The needle may go higher if the fans are thermostatically controlled.

[adzs12]

The fans are on a manual switch which are on 99% permanently.

[silviagod]

the fans only cool what is in the radiator and the thermostat opens at a set temperature and sends the water to the radiator to be cooled. if the water in the radiator is cool already it wastes energy keeping the fans on. If the thermostat is opening too soon the engine will not be running at the required temperature and the oil may sludge up and foul up the inside of the oil galleries over a period of time. Also the engine may use more fuel than it should if the ECU temperature sensor doesn't get to the designed temperature and provide the correct resistance.