[boostedbrick]

Ive had issues with a high idle, and on occasions a very slow throttle return. I have no tacho fitted so im just going by sound here, average idle is around 1500rpm, it will occasionaly rev up to around 2500rpm. After high speed stints(90kph ), if it sits and idles the revs sit around 1500rpm and will drop off rapidly and comeback several times, for a minute. On other occasions, if i give it a rev from idle it will take several seconds to come back down. A few times it has dropped down the idle for a set of lights but highidle returns again the next sit.

I have disconnected the TPS well running, it dies for a quick second and revs return to 1500.
I have sprayed the entire intake manifold and all vacum lines and have found no leaks.
I pulled the throttle body off and cleaned it.
I have a cone style MAF, ive cleaned the contacts but can see no way of cleaning anything else in it.
My ecu is incapable of providing codes so im not sure if there is another issue here.
I cant see o2 sensor been an issue, as they don't affect idle speed?

[JrZook]

Whats your radiator level like?

[boostedbrick]

Radiator is full. Gets checked regularly.

[royce]

pull the plug for the IAC valve on the manifold, that way you can tell if its a mechanical fault or the ECU instructing the engine to do it

[boostedbrick]

Unplugged it, and it ran for about 5 seconds with a low idle. Then it stalled a wouldn't start again.

[Taylor74]

Are the water hoses going to the throttle body warm, It has a wax pallet cold start valve and they get blocked sometimes causing similar probs. Check that first, often the simple things that are thought of last

[boostedbrick]

Is the top hose or the bottom hose the feed line? With the top one removed i get a very slow trickle out of it. If this is the feed theres a blockage down the line. If this is the return the cold start valve has issues im guessing.

[SierraDan]

What does it mean if you unplug the IAC plug and the idle drops from 1600 to 1300?

[SierraDan]

Radiator is full. Warm. Can't find any vaccum leaks. Pulled the MAF out, cleaned the plug and sprayed air into the sensor.
It just happened randomly yesterday.

[SierraDan]

Fixed it. Pumped air into the IAC coolant line.