Hi guys, I have a wierd problem in my xg ute (running EB style engine, thus why i have posted here).
I have used the search function and haven't really found the answer to my question as of yet. So if you could please help it would be very much appreciated.

When my car is idling it seems to drop down to my base idle setting of 600rpm and not sit at the 675rpm to725rpm like it should. When you rev the car it will hang at 1100rpm for about 5 seconds, then drop down to 900 and slowly decrease back to 600rpm. When i measured the voltage on the signal wire of the idle speed controller, it shows that when the car is idling at its base idle of 600rpm the voltage is maxed out at 14.04v. When you rev the car and let it go back to idle it will show 10.8 and then go to 10.9, 11,11.1,11.2 etc until it hits 14.04 and my revs drop back down to 600rpm. While the voltages are cycling down the car is actually idling where it should be, around 725rpm (it is a manual).

When the air conditioner is on the car does a loop. The car will idle at 600rpm, when the air compressor kicks on it will idle at 800 (obviously the isc is doing something). Then the voltages on the signal wire will start increasing until it reaches 14.04 and the idle drops to about 400rpm (base idle plus the load of the compressor making it less). Then the aircon compressor will kick off and the idle will go back to 800. It repeats this process over and over again. It usually takes 45 seconds or so to do one loop.

WHAT THE HELL IS GOING ON!!!!!!

I have had the throttle body off and cleaned it twice. I have a new throttle postion sensor which is showing the correct voltage of 0.71 at idle. i have had 3 isc controllers on this thing, my original, a 2nd hand from the wreckers and now a new one (genuine ford) and it still behaves the same. I have been checking for vacuum leaks and have fixed one (as my car in on dual fuel it was sucking in fresh air from the front rocker cover from the pcv as the back of the rocker cover only has an oil breather on it. I plumed this to before the throttle body instead of after, and things have been better but i am still left with the problem i have mentioned above. I don't know what to do!

I have been around the engine with some crc, spraying on every gasked i can find on the inlet side to see if the idle picks up, and nothing. I sprayed around my injectors to see if they where leaking and nothing changed.

I have even gone to the extent of re running the signal wire of the isc to the computer and took out the pin on the ecu plug and put the newly run wire through to see if this made a difference, but still nothing. I have also reset the ecu a few times (leaving the battery terminals off for about 20 mins then putting them back on).

I just can't understand why the isc voltage doesnt stay at 10.8v at idle, like my workshop manual says it should!!.

Could someone out there please help. Maybe someone could try out their own isc at idle at see if it is 10.8 and stays constant. (just put a pin on the grey wire with the white strip on it on the connector plug for the isc with the other wire being a red power one, then measure the voltage off the pin with a multimeter.)

I am at witts end with this issue and its annoying me so any input or any idea's anyone might have will be really appreciated.

Cheers,

I take it you have tried turning your base idle up 100rpm as per workshop manual? Inlet manifold gasket maybe???

I have also heard about people making a new gasket for the ISC but with smaller holes. Stops rev hangs and improves idle quality???

Just use a cornflake/weetbix box to cut out a ISC gasket.

thanks el_fairmont!

In my workshop manual it says that base idle should be around 575 to 625? but it didnt specify if that was for auto or manual? i was going under the assumption that it didnt matter?

When i turn the idle down even lower for base idle such as around 400 rpm. The isc still increases in voltage from 10.8 to around 14.04v but does do it alot slower! I never thought of turning the base idle up to 700. I will give this a go tonight and see what happens. I'll let you know.

I will also make up an isc gasket with smaller holes to see if this helps.

I had noticed that my inlet manifold was missing a bolt. The bottom bolt closest to the front of the engine. But i have sprayed crc all around this area and the idle hasn't gone up or fluctuated so i thought it was probably all right?

Thanks again. Anyone else got any ideas?????

I haven't got any idea's but I have the same problem and have begun searching on here.

Have you unplugged the ISC to check idle quality with it off? I know mine improves significantly, that is until the aircon kicks in, or the transmission is put into gear.

I noticed last night while searching for clues, that the ISC was audibly cycling a lot until it gets to the maximum 14V value. I haven't tried a new ISC as I wanted to confirm that it was actually the problem.

yeah when i disconnect my isc my rpm drops to about 600 and idles fine. doesnt fluctuate up or down.
I havent noticed any audible clicking as such. But seems that you might have the same problem as me. I'm putting mine down to either a bad ecu, or my inlet manifold is leaking somewhere, or some air is getting in the system from somewhere. This im pretty sure makes the idle speed controller max out at 14v as it can't control the idle it just closes. (from what i have googled).

I'm going to do a broadband manifold conversion which means it will change my ecu and gaskets and i'll re do all my vacuum lines in the process. This way i know nothing is going to leak and hopefully problem will be solved. I really didnt want to start the conversion carrying over existing problems as this is a recipe for disaster, but hopefully, fingers crossed it pays off.

Bit off the topic sorry saltez but ive thought about a BBM conversion myself but have been told theres clearence issues on XG but from no one thats actually attempted it i dont believe. Have you heard anything like this?will be interested to see how it goes mate

I have heard also that there is clearance issues aswell. Through searching from the forums i have heard that one person tried it and then had to take the bbm off. Another person said that it fits and showed a picture of one in an xg show car. However the funny part was that it didn't show the bonnet down or the car even having one.

I'm not really fussed myself if it fits or it doesnt fit. I will just grab the old trusty angle grinder and grind away on the bonnet until it closes. Worst case scenario is that i have to cut a hole above the bbm manifold through the bonnet. In this case i will just get one of those big bonnet bulge scoops that you see going around on those VN's with the group A body kits or the VL walkinshaw one and make it fit. My car needs to be resprayed anyway which i will do myself later. I just use my car as one big learning project really that will hopefully turn out semi okay in the end.

When i do the bbm manifold conversion i will show pics of it fitting or not fitting once and for all!!!

sounds good mate good luck with it!