no idle when cold

**Dave O** · 12-01-2003, 07:36 PM

I just got my bypass installed, and it works great when the car is warm. If the cars anything below operating temp it wont idle at all .. when i first start it i have to pedal it for a minute or two... really annoying ... i have tried all the usual idle things, and was curious if anyone out there has ever solved this problem....
no vac leaks 9 i think see below), mass air pointed down, pressure 40 lbs, stock block +heads, cobra intake, 24lbs pro m 75... yea think thats it ... disconnected batt reset iac tps... one thing that i just noticed while tooling with it is that i can hear air which sounds like its in the intake... should i be able to hear and air in the intake at idle ? cars been having idle problems for as long as i can remember ....

**slider_buck** · 12-01-2003, 07:38 PM

if you can hear air you more than likely have a vaccum leak. take a can of starting fluid and spray around the area where you hear it at. if you have a leak the car will rev up some when it sucks the starting fluid in.

**Dave O** · 12-01-2003, 07:41 PM

yea i tried that .. i sprayed it everywhere.. i had the intake off since i first heard it and the noise is still there....

**468LC** · 12-01-2003, 07:44 PM

Originally posted by Dave O
should i be able to hear and air in the intake at idle ?

What exactly do you mean by this dave?

**Dave O** · 12-02-2003, 12:47 AM

When i was listening for vacuum leaks , i noticed that i could hear air which sounded like it was in the upper intake.. I never noticed this before (but never had to pay attention) and i'm not to sure if its a common thing .. Im the only one i know with a mustang so i cant compare the noise to anything else.. it doesent sound like a vaccum leak and i did did a vacuum test and it checked out ok...i had a typo also... it should be "should i hear air in the intake at idle".. meaning if i get close to the intake with my ear is it common to hear air moving around? i thought maybe it was leaking under the intake somewhere, but have already checked that out , and figured id ask around before i pulled it off again ...

**slider_buck** · 12-02-2003, 02:46 AM

i've been al over my mustang when it is running and have never heard what sounded like air moving. i can hear a ticking sound from the injectors but thats about it.

**mygt8a4re** · 12-07-2003, 05:14 PM

you could possibly have an intermittent vacuum leak during the 1st couple minutes of idle. this is usually associated with an intake leak of some sort(very small) either upper or lower. sorry its such a general response! these leaks usually only effect the car when its been sitting overnight & extremely cool. the expansion of metals once heated close the leak enough not to effect idle/low rpm conditions. i hate these leaks but they are possible!
do you really only notice it after the car sat allnight? even if the car sits a few hours & totally cools down yet is sitting in the sun, it may only show slight signs but not as erratic? the car behaves perfectly after a couple minutes of operation? ive found that intermittent vac leaks & heavy fuel at idle will cause this. check for heavy carbon on your o2 sensors, they totally control idle at cold start(1st couple mins) before the sensors kick in.........

-justin

**Dave O** · 12-07-2003, 05:45 PM

yea once i pedal it for a minute or two it will idle on its own but barely, then when its up to full temp it idles great. I'll give the O2 sensors a check.. thanks for the heads up

**mygt8a4re** · 12-07-2003, 07:10 PM

just for shitz & gigglez lower your fuel pressure grealty. like around 5 psi. then try when cold.....do just the opposite as well. add 5psi to it & see if there are any changes. if so it may be fuel related. if not at least you eliminated this possibility. i see you said theres noone around you with a stang, but swapping MAF's(from another scorce/brand) can tell if its MAF related, some MAF's are very finicky......also, vac leak when cold is very likely, but can be a pain to track.......have patience, good luck!

-justin

**UNTCHBL** · 12-07-2003, 08:40 PM

I'm going to say you have a leaky header gasket.

had this problem on my white car. Thought it was the e cam, changed the header gaskets and the problem went away.

**mygt8a4re** · 12-07-2003, 09:37 PM

thats funny that you mention that. when i was experienceing my idle problems that was mentioned by a buddy of mine. i checked to be sure i had no exhaust leaks to be sure. i was fine there but have either experienced 1st hand or talked w/ local riends that have had the problems i mentioned above. i have a tendancy to check my header bolts every oil change. they do come loose occasionally & can lead to exhaust leaks if not kept up with......neat to hear that again!

-justin

**Dave O** · 12-07-2003, 10:37 PM

actually i do have a slight tick coming from the driver side.... that can affect idle huh ? hmmm... i think mines leaking at the collector though... same effect ?

**5150 LX** · 12-08-2003, 07:37 AM

Dave, have you removed the smog equipment? If so, check the holes that you sealed at the back of the heads. I've had the threaded inserts vibrate loose on me and create what sounded like a hell of an exhaust leak, took me forever to track that one down.