VS Idles to fast when cold, what are IAC & MAF

[dpayne]

Hi all,

My VS is idling to fast for to long when cold. I have been reading other comments and it appears I may need to clean my IAC and MAF. Problem is I don't know what the acronyms IAC or MAF stand for. Can anyone explain?

Thanks

 

[CHANDLC]

How fast is to fast for your idle, I'd say it would be your throttle position sensore

 

[HIROLLA]

When i start my car it idles at about 1200revs for about 20 seconds then drops to 700-800. i just wait till the revs drop before driving off

 

[dpayne]

In response

It's only started recently, and so far seems intermittent, but it will idle at around 2000 rpm (its like in older cars when the auto choke used to stick). I give the engine a little rev, but that won't correct it, even if the engine has warmed. Later on the same day if I travel some where else it will work fine and will idle arround the 800 to 1000 rpm. I have also noticed lately it takes a couple of extra revolutions before the engine fires, and the pick up when accelerating is a little flat (I have a 95 VS Exec 5 spd 3.8ltr 175k kms). I also haven't been driving it that often lately (catching buses during the week to work).

 

[HIROLLA]

I think it might be the plugs/leads how long ago since they have been replaced?

 

[semi]

IAC= idle air control- controls your throttle body at idle to run faster/slower. When your cars cold, the IAC opens the throttle a little more to heat up the engine. sounds like this will be your problem

MAF= mass air flow (pretty sure). Measures how much air is running through your throttle body/intake and adjusts the amount of fuel injected to suit. probably wont affect your idle speed much.

might want to also check your coolant temperature sensor, if its stuffed the ECU might think that the engine is cold when its not, and run the car higher to heat it up

 

[dpayne]

I replaced the plugs and leads about 18 months ago, when I replaced the three units that I guess replaced the old distributor system, that the leads now go to (one was faulty so as a precaution I replaced all three). After reading other threads I thought it may have been the IAC sensors, or the MAF if I could work out what they are.

The only other problem I have, but I don't know if this may have an impact, is that ever since the car was new, the bearing in the fan/air sensor thingy (the square aluminium looking unit with wires on the air intake hose after the air filter unit, but before the intake manifold), has always been very noisy until the car warms up.

 

[hako]

That square aluminium unit in the intake is the MAF and works on the hot wire principle (I think) and shouldn't make any noise as it has no moving parts. You should runs the fault codes and see what numbers turn up (see "how to's).

 

[dpayne]

Looks like I have an appointment with a VS service manual at the local library this weekend to work out where the IAC sensor is, learn more about the MAF and possibly, after more reading of threads, research on cleaning the throttle body. I will also take the latest advice and check for service codes.

 

[dpayne]

Looks like I have an appointment with a VS service manual at the local library this weekend to work out where the IAC sensor is, learn more about the MAF and possibly, after having read more threads, I may research cleaning the throttle body. I will also take the latest advice and check for fault codes.

Thankyou everyone for your help. :thumbsup: