hello, im just curious about my idling for my E34. The engine is m20b25,
and my idling is 950rpm. tested a few of my frens car and all of them are 600rpm. erm... that 950rpm is the lowest can go, even after turn the ilding screw untill finished. how can i lower the rpm?

mm 700-900rpm is norm for m20b25.. 1950rpm .. could it be ur ICV ? (idle control valve)

wks79 wrote:

mm 700-900rpm is norm for m20b25.. 1950rpm .. could it be ur ICV ? (idle control valve)

correct. check also yer afm.

i swapped with my e30 icv & afm to my e34 which runs the engine at 600rpm, but when installed to my e34, the rpm runs at 950 near to 1k rpm,then took the throtle body as well, still the same 950rpm...
the car runs smooth even tho rpm like that, is just that during traffic jam, my fuel went down so fast

eezuan wrote:

i swapped with my e30 icv & afm to my e34 which runs the engine at 600rpm, but when installed to my e34, the rpm runs at 950 near to 1k rpm,then took the throtle body as well, still the same 950rpm... the car runs smooth even tho rpm like that, is just that during traffic jam, my fuel went down so fast

I suggest you to retune your engine. your ride both are Manual or Auto?
If auto trans, it is normal to have slightly higher RPM idling. This is to coop when you engage your gear to 'D'.

After i run through your topic, i kinda thinks that the culprit is the acceleration cable. mungkin it got corrosive inside and got stuck. also maybe your elbow hose (afm to Throttle body) bocor. as you said, you already turn the screw and still the same. Check your vacuum host whether its secure or not. Some cases, extra air got suck in that made your engine rev slightly higher.

Try luck ya

in order to check for vaccum leaks, spray some carb cleaner onto the hoses while the engine is on, if theres any changes in engine speed, definitely the hoses need to be changed.

Accelerator cable is a must to change if you havent, i changed before and my god, its silky smooth now!

first of all would like to thank you and really appreciate to all of you guys for giving opinions.

ok, i will tell what i have already done for the engine. The story will be quite long... hehe..

1. the original engine was 520 manual 12 valve(rpm was 950k)
2. change the 525 engine (only head and block)(same rpm 950k)
3.change 525 afm,throtle body,injectors(still rpm 950k)
4.change all new hoses.(still rpm 950k)
5.change computer box 525.(rpm 600 but the throtle responsed was delayed badly, when push accelerator, the engine lag for few seconds the only it responsed even tho after tuned afm,tps and throtle screw. the fuel consumption was good using 525 comp box. but the driving was sucks!and no power)
6.so, i change back the 520 comp box. everything was fine, only the rpm is higher than normal and fuel consumption very bad. full tank oni can go up to 250km- 270km! )there was one time i had the perfect tune which the rpm was 650k(i dunno suddenly like that for two months after that back to 950k rpm).... during that time my car can go up to 600km full tank.
7. lastly,changed fuel regulator.still the same

mmm that is a long list....
are you using open port or box air filter? O2 sensor?

yes, im using both of them...
but still, before and after putting them, the rpm was the same thing...

i read again your number 6, ----->there was one time i had the perfect tune which the rpm was 650k. what are they tune? can you send to them and retuned again?. wow, i've google yet can't find the answer. there must be something wrong....mmm

bro.... the problem is, everything i tune myself.
that time, the perfect tuned at 650k was actually never tuned.
it just happen like that after i start the car in the morning,
it was at 650k rpm after that, and it last only until 2 months..then,, back to 950k again...

please send to your mech for diagnose for any electrical failure.
so far, what you did is right, vacuum hoses, ie throttle body boot, large vacuum line from boot to the idle speed control valve, throttle position sensor (tested good with ohm meter), o2 sensor (tested with multimeter) and you cleaned the ICV.

what you can do is, use the 2.5 ECU, 2.5 AFM and send for tuning to get the right setting and see how it goes. NO DIY this time.

where is the good place for tuning that? is the ICV for 2.0 and 2.5 the same?

eezuan wrote:

where is the good place for tuning that? is the ICV for 2.0 and 2.5 the same?

Try to fit all to 2.5 specs. ICV 2.0 and 2.5 i'm not very sure...
but i know there are 3 pin and 2 pin L & T shape icv...

erm... ok,, ill try to send first la..then will update here..thanks bro!