Hello again all! I have been fighting a cold start issue here recently. I have a 99 f350 v10 srw 4x4 116,xxx. If i let the truck sit for and more than a day or two, when i fire it up it will fire fine but has a miss for about 15 to 30 seconds or so and then just smooths out and runs 100% normal. It has no check engine lights of any kind, ect. Also if I drive it every day it doesn't happen or if it does it is only for about 3-5 seconds. I replaced the fuel pressure regulator, all plugs and coils. cleaned MASS air, TPS, ect. Could i maybe have a leaky injector? I am thinking i might need to get myself a good live data scanner to really pinpoint this one but am just wondering if anyone had any ideas?? Thanks in advance!

 

Your idea to connect and read the live data is sound---I'd do that quickly.

The advanced level scanners can do a "buzz test" of the injectors to better gauge how they're preforming. Ideally you could connect the scanner after its sat still for a few days to see if one of the injectors is indeed acting up.

I'll assume you changed the spark plug boots too---or at least carefully inspected them? Was there any coolant or moisture in any of the plug wells?

 

All good points... The only thing I would add is, if you can read live data, try checking the misfire counters when this is happening to make sure it's actually a misfire.

 

Yes I did replace all boots with cool packs. I put some dialectic grease around the outside of the boots just a thin layer to hopefully prevent any moisture from seeping in. I think a live data scanner is probably the way to go to see what's going on. I believe it has to have an issue with an injector but I could be totally wrong. I just recently put a new water pump, radiator, thermostat, and heater core just to freshen up the cooling system. The issue was there before and after this. I haven't lost any coolant and everything looks very clean so I'm thinking I'm ok there. I remember when first getting the truck years and years ago I used to be able to get 12-14 mpg on the regular and recently I couldn't even get 10. It used to puff a decent cloud of smoke, (fuel) on start up and then clear up and be fine. I had the infamous heat and a/c out the defroster vents for a long time and finally figured out that it was a part by the passenger front fender. Looks like an egr solonoid. I believe it has something to do with fuel vapor... I bypassed that unit and plugged everything into the vacuum canister and my a/c, heat, ect all work perfectly fine now and I think I picked up maybe 1 mpg. I'm thinking I need to buy that part (whatever it is) and fix that right also. At least I narrowed that down... It was extremely frustrating to diagnose because I kept looking for a vacuum leak for literally a year before I realized what was going on lol

 

I think if you hook up a fuel pressure test gauge to the fuel rail test port you might see something.
If I remember right ours would have around 35 psi at idle and still hold 25 psi 3 hours after turning off the engine.
If an injector was leaking the pressure would bleed down faster than that.

 

And that would explain the puff of white smoke on first start up. Wouldn't hurt to install the fuel pressure gauge as well as pulling one or a few of the suspected spark plugs seeing their condition.

 

28-30 psi at idle, 38-40 psi under load, or there abouts on the 2-valve V10s pre-2005 (not sure about 2-valve after 2004).

The vacuum related thing on the passenger fender sounds like the ESOF hub vacuum switch - do you have the 4x4 **** on the dash?

 

Yes I do have the **** on the dash. My 4x4 never worked with the vacuum ever since I bought it years and years ago so I just always locked the hubs in. I actually removed the lines one day when i was bored. That would make since if that's what it is lol

 

Really good idea on the fuel pressure test guage! I will definitely try that for sure! Ordered a live data scanner also. Should be here momentarily. Thanks for all the help guys!

 

When you said you "bypassed" that solenoid on the passenger fender well, what did you do? Block it? or just connect the two lines that went to it?

 

I just put the lines straight into the vacuum canister/ reservoir. I believe I did one up top and one in the bottom. Been a while

 

One of those lines from the ESOF solenoid goes to a "T" and then to each front wheel. That could be another vacuum leak. The line TO the solenoid would have come from the reservoir, or near it, and the other would go down to the wheels. They should have been both plugged.

Look at that, trace the lines and see what's what before you go any further.

 

Yea I capped them off years and years ago

 

The rubber deteriorates, worth checking again.