Cold start rough idle/lean problem

[SilverXJ]

I'm going to replace the injectors and see if that helps.

I've narrowed it down to two options:
Bosch 0-280-155-784 238cc/22.6lb @ 43.5psi; 252.6cc/24lb @49psi from a Neon
Bosch 0-280-155-789 240cc/22.8lb @ 43.5psi; 254cc/24.2lb@49psi from a Caravan 3.3L FFV
Those numbers are accurate to the best of my research. The values at 49psi are calculated as all the flow ratings are done at 3 bar or 43.5 psi. Both are have USCAR connectors and 4 holes.

I was set on using the 0-280-156-161 from a Ford Focus which had 12 holes. That was until I saw a spray pattern, which is very wide.. most of the fuel would end up on the sides of the head port, not really directed at the valve like stock.

Any opinions on which ones?

[BDD]

It couldn't be caused by a loose intake could it? A month after i built my stroker it was idleing funny when cold,i found my intake bolts had loosened up causing a vac leak,when it warmed up it would seal back up.I tightened the bolts and havnt had a problem since.

[SilverXJ]

That was one thing I though it could be, but I checked the bolts, ran an unlit propane torch around the intake and sprayed cleaner around the intake and didn't find anything. Also, it doesn't see like it lasts long enough for the head/intake to build enough heat to seal it.

[banipal19]

Did you figure out the problem? I have the same issue but never got around to check it. Been too busy with a kid on the way.

[SilverXJ]

Not yet. Its definitely a lean/lean misfire issue. It only does it until the O2 sensors are up to temp, like a minute or so.

I was able to make it better by adding fuel at those points using the AEM, but while it made the cold start better it screwed with the driveability when it came back through those cells.

I swapped to about 24 lb injectors and little to no change.

There are no vac leaks.

There have been a couple suggesting its the cam, but I don't see how. Its probably the most popular cam that Hesco sells and their least aggressive cam as well.

I may try swapping back to the stock injectors, but first I may change the MAP sensor with a spare I have.

I'm also going to go back and check the fuel pressure again and maybe mess with the Cam sensor a bit.

[Brian E]

Whats your throttle position voltage at idle cold versus hot? I had a TPS that read fine hot but cold it had spike coming off idle.
Also the IAC valve, is it possible its not closing all the way and or sticking and not moving smoothly enough to prevent a off idle cold miss. I have also seen people mess with the the throttle body stop screw and the IAC could not make up for it enough. Just other thing to keep you from sticking to one thought. I've been there and sometimes it helps to change your thought process. Good luck.

[SilverXJ]

TPS is good, checked. IAC, well I don't know how to test it, so I just replaced it. No change.

The IAC is definitely working, but I wonder if its working too much. I wonder if I disconnected it a hot idle what would happen on the next cold start.

[SilverXJ]

Just an update. PCM reprogram for the cam solved it. It now starts like a normal vehicle. I guess the Hesco. RVOB was just a bit much for the stock PCM to handle. Got it done by [email protected]. He is very knowledgeable and will try different things and work with you to get what you want. Definitely not an off the shelf tune. Did a few other modifications in the process as well.

[Retlaw01XJ]

Add my 2001 4.6 with mild Crower 44243 cam to the list of owners with the cold/lean rough idle at startup. Lasts for the first minute or so.
I was often getting O2 sensor heater fail codes, even with one of the new Bosch sensors. Once the light is lit, it'll run lean until I reset it...... real annoying.
Runs great once it warms up a bit.
Vacuum is at 19 at idle. I'll run thru the other checks Silver mentioned just to ensure all is operating as it should.
Initially used the stock injectors which worked well overall. Recently installed some '01 Ford 3.8 liter XR3Z injectors rated at 240.2 cc/min or 22.85 lbs/hr (at 3 bar/43.5 psi) which made little difference.

I take it the PCM update richens the fuel mixture for the cold start-up.....does that require the vehicle be taken to a specialist or can the PCM be shipped to him?

[SilverXJ]

The PCM can be sent off to him for the reflash. He can also do a bunch of other modifications.

The cold start problem lasts until the O2 sensor has reached operating temp and the PCM can use it.

You may also have another issue in the heater circuit for your O2 sensors if it is giving codes. Check the fused for it as well as associated wiring. Its not uncommon for wires to have rubbed through on a drive shaft or some other part.

[RayRay]

my 4.6 done the same thing to me. on cold starts it idled like it had 3 bad plugs(every other cyl.)in it. when colsed loop kicked in it smoothed out and ran fine. i replaced both UP FLOW o2's and the prob is but a memory. open loop isnt post to use o2s though right? tables in ecm right? worked after i tried EVERYTHING else! go figure.

[Coffee Commando]

I take it that when I convert to my supercharger that I'm going to have to create some sort of addition to the vacuum system due to the boost in the manifold. ???

[SilverXJ]

No, you put the vacuum ports for brake booster, HVAC, emissions, etc. before the supercharger.