fuel economy & ISC

[dannyboy77]

open to anyone of course

Vince I see you have taken off the ICS on a couple of conversions? Is that to clean them or because you taken off the inlet manifold? I think I am somewhere closer to finding out why have poor fuel economy on petrol and LPG. What do you think of the following? I have checked the ISC, resistance is fine but when put voltage through it none of the valves worked and the valve shaft did not move but you could hear the valves click. So I think it is broken.

To back track a bit when got the LPG conversion the guy put a valve on the pipe from air inlet pipe to the ISC and had it virtually closed which mean it idled OK when at temp but needed foot on pedal when starting cold. Now I have removed the valve it starts fine when cold and idles 2000 rpm when at temp.

The thought for running poor fuel economy is the temp sensor is telling the ECU when it is up to temp which then gives signals to the ISC to vary the air, being broke its stuck in cold / open position letting a lot more air in than needed, then the O2 sensors are reading lean mixture and dumping more fuel in hence idling at 2000rpm??

Any thoughts?

[dannyboy77]

just taken the ISC apart and the top bearings are rusted so going to give them a clean and it should free it up. guess the resistance of the rust on the bearings were too great for the magnet to spin the valve shaft up and down??

[BUSHWHACKER]

just taken the ISC apart and the top bearings are rusted so going to give them a clean and it should free it up. guess the resistance of the rust on the bearings were too great for the magnet to spin the valve shaft up and down??

Absolutely!

Inside the ISCV is a stepper motor that adjusts the amount the shaft moves in and out. I make sure they're clean and spin free with no notchyness in them.
There is a way of testing the ISCV by earthing one of the pins and applying 12v to each other pin in turn in a clockwise pattern to see if the shaft moves out/in. I can't remember off the top of my head which pins though.
You should be able to hear it clicking as it adjusts itself to the cold start position every time you switch the ignition off.
If you make a note of the serial number on the bearings, or remove them, you can get replacements very cheaply from bearing suppliers.

Are your O2 sensors staying in open loop? That would cause over fuelling.
Are they the for wire type with heaters or two wire type?

[dannyboy77]

yeah i have the FSM trouble shooting page for the ISC so have tested it and powered it using 12v laptop charger can hear it clicking but no movement so took it part and seen the rust on the bearings!

its just how much it alters the fuel economy being in cold position all the time. still need to test the ECU to make sure all correct signals are going to it at the right time. will test temp sensor, air flow and throttle sensor. does the cooling fan temp sensor make any difference? its next to the main temp sensor

the O2 sensors are not toyota as i got different exhast manifolds so they are universal 4 pin ones and i know they work as i get a reading between 0-1v 5times a second. FSM says thats right if get 0v or 5v reading then they are knackered! but they arent top quality ones btw.

[dannyboy77]

cleaned up the bearings in the ISC but still it isnt opening or closing so i think the electric element of the of the ISC is bust so i think i need a new ISC know of any second hand places??

[BUSHWHACKER]

Explain to me how you tested it.

[dannyboy77]

I tested it like FSM said battery power to the middle 2 and went around in sequence S1-4 4-1 you can hear it click and see it wants to move up and down but it doesn't. The bearings are OK I 1-3 oil and WD-40 them and they move freely infact the valve shaft springs up a bit when all the way down. The resistance test was OK giving 22 OHMs On S1-4.

[BUSHWHACKER]

Did you go 'round each pin a number of times or just once?

It takes quite a few times before the shaft starts to move.
I haven't seen the diagram you mean so I don't know what it says, but if your valve is clicking then I would say is working OK.

Next thing you need to check replace is the EFI temp sensor (the green one next the the temp gauge sender) This acts like an auto choke of carb engines. It senses the coolant temp and then tells the ECU to lean off the air/fuel ratio (turn the choke off) as the engine warms up.

I get mine from here.....
http://www.rovercarpartsuk.co.uk/p25...-Model-Product

Do you have a cold start injector (ninth injector) in your intake plenum?
If you do the you could see how your fuelling is with it un-plugged. It doesn't get cold enough here to need it to be honest, the UCF20 engine ('94 >) doesn't have one at all.

[dannyboy77]

did try it a number of times going around in order you can hear it click and want to move up but doesnt. dont know if when it ceased up it damaged the magnet or coil or something?? i have a quote for £51 for a second hand ISC from a breaker.

i have check the EFI temp sensor for resistance and voltage (only cold though) it read right resistance and between 3-1V for 20c think it has to read 0.1-1v for 80c . what is the other temp sensor nect to it in the FSM it says it the cooling fan sensor it only has one wire? is it imoportant? think mine is 1991 so you are saying it wont have a cold injector?

[dannyboy77]

i checked the temp senosr too it was reading 0.05v when at 80oc so less than the 0.1-1v recommended by the FSM so i will be getting a new one, then i will test the ISC and see if that works now the ECU will have a reading from the temp sensor.

[BUSHWHACKER]

i checked the temp senosr too it was reading 0.05v when at 80oc so less than the 0.1-1v recommended by the FSM so i will be getting a new one, then i will test the ISC and see if that works now the ECU will have a reading from the temp sensor.

Renew the temp sensor and that should be the end of the problem.

[dannyboy77]

nightmere! got temp sensor, fitted it and engine light came on giving 5v so it was a dud! took it back that worked giving 0.5v at 80oc so all good but idling at 2000rpm at 80oc
so got second hand ISC, its different to the one i have as you cant unbolt the black section off it. tryed the FSM test on it and the valve didnt go up or down but tried it any way and again idle at 2000rpm at 80oc

for f@~ks sake doent anything work!

[BUSHWHACKER]

Did you re-set the ECU after replacing those parts?

[dannyboy77]

i havent actually i will do. keep up posted!

[dannyboy77]

took the positive terminal off the battery for 11hours and was a bit better it reved at 1400 rpm at temp when should be idling at 700rpm so i checked voltage on the O2 sensors and OX2 was 0.6v constant and OX1 was 0.05v when idling at 2000 rpm so i think there is a problem with the sensors will check the voltage of VF1 & VF2 to see if it is 0v or 5v or is OK but i think the sensors might be on their was out maybe.
if the VF voltage is 0 or 5 then look at the table to in trouble shooting to see what the problem cause could be.
vince did you put resistors to give 0.5v on the sub oxygen sensors to trick the ecu? feel like doing that with the main oxygen sensors!?!?