Crappy Idle On Cold Start

[5.02GO]

OK. Here is another silly problem i have.

On cold start up, my motor has a hard time holding an idle. It starts up strong but when it slows down, it almost dies. Once it finds an idle, its a good one and it hold it.

Here are some specs.

Fuel pressure - 45psi
Bypass Valve - Yes, bosch
C&L 73 with 30lb sample tube
Paxton cover is over the filter.
Timing - 8 degrees
Ignition - Stock, i do have msd 6btm but not currently hooked up.


I havent tried re-clocking the mass air yet, but will later. I also have an Idle Adjustment Plate installed. I havent heard anyone talk about it yet but, i goes between the idle solenoid and the throttle body. Here's a pic.

[Whistler]

I would try clocking the MAF and see if that helps. For some guys, it makes a HUGE difference in the idle/driveability characterictics. My car idled silky smooth when the MAF harness was straight up (at 12:00).

See if clocking the MAF helps your idle. It may not be the 'cure all' solution but it would probably help.

[Goliath5.0]

Check your TPS voltage (be sure to disconnect the IAC PLUG), adjust (.94 -.99 volts) as needed to where your car likes its. Turn her off, reset the computer by removing BOTH battery cables, leave the car alone for a couple of hours (just my recommedation), come back connect the battery cables, and IAC PLUG, then start your car, IMMEDIATELY turn your A/C on to MAX let the car sit and re-learn the new idle adjustment, sit for about 5-8 mins, turn a/c off and presto! If it was the tps sensor that was the culprit, the idle should be fine now!

[mygt8a4re]

if it does it everytime you start the car when its cold(usually sits overnight) but finds the idle again after a couple minutes i would suggest a probable vacuum leak. i had a very small vacuum leak after my heads/cam install that would only show at cold start up. after 2 minutes it would idle fine, every time. but th 1st couple minutes it would dip out & hunt a bit at low rpms. ended up having a hairline crack in the vacuum tree, replaced it & it ran perfectly...............ive seen small vacuum leaks become endless frustration for many of my mustang buddies.......

[Goliath5.0]

Good points dan and mygt8a4re keep'em coming :D! So many little things that can cause our idle to get screwy.

[mygt8a4re]

man ive had so many idle problems in the past. i had the TPS idle problem, then the dirty IAC sensor idle problem, then the vacuum leak idle problem & the all to well know ford E or B cam idle surge problem.............wich by the way reminds me, pull the IAC valve off & spray the heck out of it with t.b. cleaner. spin the plunger inside to gt all the deposits off of it & move it up & down to be sure its free.
as far as vacuum leaks are concerned, its very hard to be sure you do not have one unless you actually do a vacuum check test. if a leak is found it needs to be performed in numerous locations to pinpoint it. the best place to start is to think about what you removed or messed with last that has a vacuum connection. if you messed with nothing then it can be a real "hunt" for the leak. think of all the gasket locations & hoses..........each need checked carefully.

-justin

[regattacoupe]

I've always had hot start issues with my C&l. No problems cold but it is a bear for about 45 seconds when it hot out and it's @ temperature. Hopefully a pro-m can fix that.

[5150 LX]

Originally posted by 5.02GO
I also have an Idle Adjustment Plate installed. I havent heard anyone talk about it yet but, i goes between the idle solenoid and the throttle body. Here's a pic.

I've got one & it worked pretty well for me.

[mygt8a4re]

the idle adjustemnt plate deffinately works well. it was actually made by ford to ease idle problems caused by carbon build up in the IAC & throttle body area. it allows you to let more air pass through than the IAC is letting through. but this problem was to keep idle right when carbon would build up in those areas, so if this fixes your problem ten cleaning those areas could also fix it. BUT! the option of adjusting idle free from having to change the TPS every time is a great plus by itself........those idle plates were godsents for those with the E & B ford cams due to thier hunting idle characteristics! (not sure why i added all that, lol!)

-justin

[5.02GO]

Originally posted by mygt8a4re
the idle adjustemnt plate deffinately works well. it was actually made by ford to ease idle problems caused by carbon build up in the IAC & throttle body area. it allows you to let more air pass through than the IAC is letting through. but this problem was to keep idle right when carbon would build up in those areas, so if this fixes your problem ten cleaning those areas could also fix it. BUT! the option of adjusting idle free from having to change the TPS every time is a great plus by itself........those idle plates were godsents for those with the E & B ford cams due to thier hunting idle characteristics! (not sure why i added all that, lol!)

-justin

You better believe it about the E & B cams. That plate was a miracle in helping the motor idle properly with those cams.;)

That little thing was a night and day difference.

**I unplugged the battery today for a hour or so. I didnt make much of a difference on the idle.

I did notice something though. While the motor was running, i put my thumb over the oil neck vent ( i dont have anything hooked to it). While that vent was covered with my thumb, the motor built up a vacuum. Should that be plugged?

I know that vacuum is coming from the PCV. But if i DONT have it plugged, wouldnt that be the same as a vacuum leak?

Thanks..............

[mygt8a4re]

i wouldnt consider it to be a vacuum leak, its just pulling in unmetered air during idle as filter on the end of the filler neck would do, only it would be filtered! i would suggest capping it.........

-justin

[5.02GO]

Originally posted by mygt8a4re
i wouldnt consider it to be a vacuum leak, its just pulling in unmetered air during idle as filter on the end of the filler neck would do, only it would be filtered! i would suggest capping it.........

-justin

I am gonna try it.

I got this off of "pro-m's" website. Anyone tried this?

Crankcase ventilation improperly installed; causes lean idles and lean pops at light loads and medium speed (1700 to 2500 RPM).
Throw away any breather to the crankcase that does not connect to the downstream side of the Pro-M meter.
If you have a turbo or Super-charged system the crankcase vent must be enlarged (5/8 inches to ¾ inches) and again plumbed between the Pro-M and the inlet of the super-charger/turbo.
If you must have your crankcase breather vented to the atmosphere, plug the line to the PCV valve at the manifold. This is illegal for road use and of doubtful benefit, but it will drive somewhat better and let you use a breather vented to atmosphere.
Check PCV valve for correct installation; on GT-40 manifold, the PCV valve is located so that the hose is short, and it sometimes pulls the valve out. This will cause idle problems and lean running at part-throttle loads. MOST COMMON PROBLEM!
Check system for vacuum leaks and fix them.

thanks

[mygt8a4re]

just to note, i know several supercharged mustang owners that have the oil filler neck breather vented to the atmosphere & are problem free, includin myself!
good luck!
-justin

[5.02GO]

Originally posted by mygt8a4re
just to note, i know several supercharged mustang owners that have the oil filler neck breather vented to the atmosphere & are problem free, includin myself!
good luck!
-justin

I just tried capping the vent on the oil neck. When i took the fill cap off, a huge rush of air went in. I decided NOT to cap that little vent. It cant be good to do that.

I noticed something. There was a light coat of oil or residue on the intake, cap & rotor and other various things. If i didnt know any better, i'd think that the PCV valve is leaking boost into the crankcase. Now i am thinking of getting an new PCV valve. Or just plumbing a hose from the PCV to between the blower & mass air meter.

Hhhaaa.........Decisions, decisions.