car is totally standard big turbo.

Hi, my car is hunting at idle and at low revs.

On cold start up, the car is fine. although it idles at 1300rpm, which is a bit high. think i will need to adjust the screw for this 950 if the norm yes?

as the engine warms the hunting increases and at full operation temp its very bad. 900-1600 every 5 seconds!!!

a pain in the arse as the car is undrivable unless im accalerating and also very embarasing when in traffic. trying to drive at 30mph is near impossible as the hunting acts like in on off the accelerator pedel every 5 seconds, look like a learner kangerooing!

if i take the small vacum pipe of the inlet manifold then hunting stops!!!

so logically i replaced the map sensor as its this that the pipe leads to. but with no joy!!??

i have been told the idle control valve on the inlet a piston inside can stick. ive taken this off and left the bottom half/piston end to bathe in some engine degreaser.

i will put it back and see if theres any luck.

there doesnt seem to be any leaks.

has anyone had a problerm the same as this. any advise would be appreciated, as its such a simple thing but is making the car undrivable/ unsafe.

 

I would think that after you have cleaned the iscv then it should be ok as it sounds like thats the prob mate.
Good luck

 

it's normally the iscv being gunked up

cleaning it might do the trick but sometimes the plunger is faulty and cleaning won't solve the problem

make sure you use a new gasket as well

 

I would also check the CO at idle, and the TPS output.
tabetha

 

how do i check for this? is than not to do with the lambada/ hego sensor?

also what does TPS mean? throtle position sensor i guess? again how would i check this and where is it?

will put ispv back in later, hope this solves it!

thanks

 

Yes CO at idle controlled by lambda, UNLESS it is faulty!!
When they go duff, they can still have a good within scale lambda reading but the switching speed drops off, the result is usually going way off scale mixture wise.
The tps is just tested by seeing how it reads as you slowly open the throttle, that is about all you can do, sometimes you find it has a dead spot around idle or near there, is the common place but could be at any point.
tabetha

 

right ispv cleaned, but still no luck!!

im mate (a ford technitian) reckons we should look at the ecc control valve (think thats what he said?) next, and check the vacum is pulling about 19 on the mercury scale. as this could be sending false readings there for the car over fueling then conpensating buy underfueling then more fuel again etc.

My (lambada) hego sensor wires are a bit worn, so i may try replace this also.

 

Think he meant ECT sensor bud thats the coolant temp sensor,

 

try to check your tps..
while opening the throttle check the Ωhm must be 600 to 40(from close to fully open)

 

you must only set the idle to 950 rpm once the car is up to temperature, sont try and ajust this as its warming up. it should hold at around 1300 then drop back slowly after a few mins, it will take 15-20 mins to be fully up to temp, then disconnect the cable off the idle control valve and ajust the screw underneath the throttle body to get the revs to 950. when you plug the wire back on the speed should not go up, if it does then i'd d say trhe thtottle position sensor is out or the coolant sensor if fooked.

to set the tps, with the wires connectdm, you need to undo the the throttle body which has it connected and across pins 17 and 19 IIRC, the voltage should be at idle 0.25 to 0.3 volts DC, incidently this will be where the ajustment of the TPS is exactly halfway along its ajustment.

 

thanks guys yes ect was what he said. would make sense as the warmer the engine gets the more it hunts!

 

normally hunting is a sign your base idle is to low,

as the iscv closes the desired idle (desired by the ecu) goes to low,so the iscv opens again to compensate...then it starts over again..


usually if the idle is hunting the iscv is working just fine...raising idle....exactly what its meant to do


to set your base idle, run engine till hot, then unplugg iscv via its grey plug...idle should not drop...if it does,adjust idle to 900rpm via screw under throttle body....then reconnect the iscv and the idle should be stable.

the base idle shouldnt be held on the iscv,with the valve closed or unplugged it should idle nicely at 900rpm


simply adjuting the global modifier,without checking fuelling on full boost is a very dangerous game, as it alters the whole fuel table as a percentage.

tps is a good posibility to,if the ecu spots an opening throttle it opens the iscv,so if tps is incorectly set it can open the idle

 

you lost me on the global modifier???

yeh the rest makes sence, i will have a play with the idle screw.

as said it only hunts when warm. before hunting starts/ when its cold it idles at 1200 which i guess is normal on cold? will have a play let you know

 

screw on ecu is the global modifier....you may not have one if on p8...


when cold the iscv creeps open to give fast idle,hence why it doesnt do it cold

 

right. ok. i understand.

i dont know much about the car management. p8 or not. ive only had the car 2 months, one of them its was stuck in the workshop with out a head gasket.

i'll tell my mate about this, were running out of ideas and this is something we havnt thought of yet. as said hes a ford technitian, so he will understand the jargin better than me.

its getting really anoying as weve got the engine felling smooth and totally bullet proof. the hunting makes it totally undrivable.

 

oh ive just noticed after going to get fuel. the temp guage in the car is not working???

this could point to the engine temp sensor, and i guess will cause the hunting when warm if the car still thinks its cold?

 

The temp gauge has its own sensor just above the ect sensor, but maybe worth changing em both as cost peanuts.
Good luck.