Engine Doesn't Like To Run When Cold.

[95Vert383AOD]

Not sure if its because of all the modifications or what but my car just doesn't like to start when its cold. I'm talking colder than 40 outside cold. If it were 60's+ the car starts and idles fine. But when cold i have to hold the gas pedal down partially. When doing so i feel what seems to be an ever so slight misfire. If i do get it to idle cold it will stall out as soon as its in gear.

-Oil Pressure is 50 Cold, 25 warm idle and 40 @2000rpm
-All Vacuum lines are new
-Fuel pressure is at 40
-Timing is 14 Degrees
-Cap & Rotor are good
-Plugs gapped to .054 (Autolite 3924)
-Module is DynaMod
-Cam is 222/232 .570ish lift
-Full Aeromotive Fuel system (Text Book Setup)
-No Emissions Stuff

I just don't get it....There are no vacuum leaks....Car runs 100% after warming up to at least over 100 degrees. This isn't a surging issue.

This isn't a new issue.....Its always done this but i figure i would ask you guys. Ive ripped down my intake 3 times in the past 5 years for various reasons this issue has always been around.

Any Clues?

Once again this isn't a surging idle. Car will die if i don't hold he gas when the temp outside is colder than 40. No surge....just DIE. Its done this for years. Hasn't gotten better and hasn't gotten worse.

Chris

 

[HISSIN50]

Assuming no codes, are the ECT and ACT in calibration at lower temps?
Is the IAC known to be functioning properly?

 

[95Vert383AOD]

The IAC is fine.
My ACT is part of my SCT meter and seems to run fine.
I'm not sure how to check the ECT but that is also a new part.

Its strange because if its really cold it will not idle at all. The colder it is the worse it is.
I had a H/C/I 302 that used to do the same thing. Different motor and different car.

 

[jcgafford]

mine did the same thing for a long time. started as just a minor annoyance and then it got worse and worse till it became a no run situation. i went thru all the no crank, no start etc. checklists and everything checked out. ended up being some part of the dizzy that was just hanging on and finally failed. new dizzy and now no problems. try swapping in a new dizzy to rule it out? this was after i spent months killing codes with jrichkers help. got them all cleared and then this really started hardcore. it never threw a code for this problem. perhaps you have the same thing starting.



edit: it was the pip sensor failing in mine.

 

[HISSIN50]

This is on the '95? Can you view PIDs?
Remember, new does not mean good. I would want to actually check calibration of those parts - and that's a lot easier if you can view PIDs

 

[jrichker]

Dumping the codes will normally show a faulty sensor. The ACT & ECT may be on the outer limits and not set a code but cause problems. Use a DVM or multimeter to check them.

The computer pin numbers are for 89-93 Mustangs. If you have an eariler or later model take the measurements at the sensors.

Pin 25 ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

Pin 7 ECT signal in. at 176 degrees F it should be .80 volts

The ACT & ECT have the same thermistor, so the table values are the same.

Here's the table: The values are +/- 15%, so don't get worried if your readings vary a little bit.

Voltages are measured across the two connector pins of the sensor with the sensor connected. Some safety pins used to probe the connector from the rear will be helpful

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor wiring disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms

 

[95Vert383AOD]

Assuming no codes, are the ECT and ACT in calibration at lower temps?
Is the IAC known to be functioning properly?

Can Timing cause the car to not stay running when very cold? My timing was a bit below 10deg. This morning it seems to be running OK

 

[HISSIN50]

Can Timing cause the car to not stay running when very cold? My timing was a bit below 10deg. This morning it seems to be running OK

If you're talking about a couple of degrees total timing, no biggie. And being retarded generally only helps it start.