fatmike

iTrader: (4)

Hey guys, just put me car back together after having the engine out and ive realised the problem with the idle is still there. Its fine as it ticks over, but when you give it some revs and let off, it almost sounds as it its going to cut out because the revs drop right down. Then a second or 2 later it picks back up to a normal idle. any ideas??? obviously its no good when your out driving thinking everytime you put it in neutral its gonna cut out. The engine has not been apart, ive just changed clutch, engine bay respray etc.
timing doesnt seem out either becuase it sounds sweet as a nut, doesnt miss a beat
its a 4x4 stage 1 290bhp. t34 2wd exhaust manifold, group a oil breather. rs500

any ideas will be great. Cheers Mike

SillyFezzaMk1

iTrader: (1)

ISCV Lazy? Get it off and clean it up aand test it.

Dan

fatmike

iTrader: (4)

Ahhh yeh idle speed control valve, ill give that a try

SillyFezzaMk1

iTrader: (1)

If you do a search i'm pretty sure theres a topic on how to clean them properly and test them I read a while ago....might help you out.

Dan

SillyFezzaMk1

iTrader: (1)

Failing that you might have upset the base idle by knocking the throttle position sensor out of line a bit....But the ISCV would be 1st point of call.

Dan

fatmike

iTrader: (4)

excellent, thanks alot mate, ive just cleaned it and put itback in and she works like a treat. funny what a bit of dirt can do.

ill have a search for that thread just out of curiousity, but for now, 2 sheets of kitchen roll and somewhite spirit have seem to have done the job

fatmike

iTrader: (4)

ok i lied, it did work ok at first and now it seems to be playing up again, i read that thread on cleanin them and it says clean it throroughly, leave it in cleaners over night. ill have to try that, failing that, it looks like a trip to the shops for a new one

JTECH James

iTrader: (13)

if the revs drop after you rev the car up your base idle is too low, as the iscv will close in these conditions untill the ecu realises the desired idle has not been met ,then opens the iscv again.

unplugg the iscv with the engine hot. set the base idle to 900rpm by adjusting the screw on the base of the throttle body. plug the iscv back in and the rpm shouldnt change.

i bet from the symptoms you have described, when you unplugg the iscv the idle will drop like a lead weight

krisberic

Just been reading this post, and i now think this is what is wrong wi mine, it drops well low when disconected

SillyFezzaMk1

iTrader: (1)

I thought you set the idle by rotating the tps slightly untill you get a certain reading from the pins........The base idle should be factory set so is it not best to look at the TPS voltage/reading 1st before adjusting something that can possibly lead to more problems?

Dan

JTECH James

iTrader: (13)

the best and quickest way to see if a cossie base idle is set correctly is pull off the iscv plug and see if the idle drops, as it shouldnt if its set correctly, think about it, the only way a ecu can effect idle is by opening and closing the iscv, if this is unplugged nomatter where the tps is set to, the base idle should remain at 900rpm, if it drops when unplugged the base idle is to low, if it rises when plugged back in, the ecu is telling the iscv to open probably a tps setting fault, at idle the iscv should be closed.

fatmike

iTrader: (4)

right ok guys, thanks for that info btw thats really helped, first step ive decided just to strip down the iscv (taking note of how many turns the nut was done up and not loosing the little springs inside ) and am cleaning it through to get rid of all the crappy soot deposits, then i shall try the method you explained above. hopefully all shall be good then. its probably never been cleaned before so its due one.

snow*

I've got that idle problem too, when I unplug my ISCV my revs drop alot, when I reset the idle screw to 900rpm and plug the ISCV back in the revs increase alot.

TPS not set properly perhaps?

fatmike

iTrader: (4)

yeh i unplugged my iscv today and realised the revs dropped extremely low, i haven't tried ajusting the base idle yet, but fear that ill probably have the same problem you do. however i must admit after stripping the iscv down and cleaning it throroughly it seems to work alot better, ill just have to wait and see

daz1968

I had similar problem, but was a combination of base idle and also lean on tickover so causing hunting, so maybe get idle mixture checked if all else fails, mine happened after rebuilding the bottom end though, so new engine was drawing different airflow on tickover, but maybe another thing to check. I just adjusted ecu mixture screw to get it right, but when finished running in will get it all checked properly.

JTECH James

iTrader: (13)

yes, or a faulty/incorrecttly adjusted iscv

fatmike

iTrader: (4)

so in that instance how would you ajust the iscv?? by ajusting the little nut tighter or looser inside the bottom of the iscv?

JTECH James

iTrader: (13)

yes it can be adjusted that way ,but most commonly the problem is the springs either side of the piston go weak with age,

if you can find springs to fit try replacing them, or stretch the old ones, but doing this is trail and error

ideally you want a base idle of 900 rpm with the valve off, the idle shouldnt be effected when the valve is plugged back in, but you want a 1200ish fast idle on cold start ,and you also want the valve to open slightly when the headlights etc are turned on ,to keep the idle at 900rpm

i wanted a new valve for mine as it was playing up, but they are very hard to come by now, they can be found in spain i think but are £300+

ive now got mine almost perfect ,with a bit of time playing with it

snow*

Mine ISCV is nearly brand new mate, as is my TPS
I guess it must be down to the TPS not being set properly

JTECH James

iTrader: (13)

could well be ,or resistance in the wiring loom