Idle Rev not stable??

[altong0840]

hi fellas~i just tuck the D15B engine back in my EG dul my last engine total lost... now the new engine idle rev just jump up and down form 300-1100RPM, not matter i start the a/c or not~it just not stable~

just want to know what will the problem be?

my fd told me maybe the auto transmission fuild too old, need change~would it be the problem??

[mars_panas]

This sounds like a messed up idle air control valve. The idle air control valve sits right beneath the throttle body. This has a plug going to it and right above it will be an intake and exit hoses, these hoses are small coolant hoses that warm up the throttle body.

When this valve goes bad it will not be able to control the amount of air going into the throttle body while at idle and therefore causing the rpm's to raise and dip non stop.

[Sir_vtec]

not just the IACV. But it can be spark plugs also, this is due to moist on one of the spark plugs. check spark plugs if u havent changed them yet.

This is from experience.

Btw is the car lagging at acceleration?

[beeza]

Such a common problem.I would clean out the IACV first because that is more than likely the culprit,then plugs and leads and TPS sensor.

[g.ta]

Ive had this problem, rev was bouncing, sometimes rev stayed really high at idle and eventually rev was so low at idle that it caused the car to stall and if you ignore the problem long enough the car wont start up (just loosen the screw on the throttle body to allow airflow via the throttle to start it)

Just take out the IAC and give it a clean with TB cleaner, usually theres a built up of gunk/dirt causing the mechanism that allows air through to be faulty/sticky thus an unstable idle speed. Theres a DIY on here somewhere.

If its still fuked after the clean you will need to replace it.

[altong0840]

thz brof but i am not sure where is the IAC valve locate`when i open the bonnet and i saw a twin carby filter holder, and i cannot see where is it.. can anyone show me with photo please...thank you very much!

[jimbean]

The term is called hunting, sounds like you got a air leak best thing to do is go through everything, one thing at a time

as said clean Iacv, check all vacum lines for splits if neither them get some WD-40 or easy start and spray around inlet manifold every thing if the rev's rise after a certain area has been sprayed narrow it down and theres your culprit, also try bleeding your coolant aswell

[altong0840]

http://www.attarco.com/images/D15B.JPG



just wonder which one is the vacum lines??

than you very much