hey guys ,,,, im having issue on cold start engine was surging and stalling after a couple restarts it was running fine so i went on the road about 1/8th mile at 30 mph it bucked so i came back home just as my front tires hit the driveway it stalled again after a few cranks at wot it started as i drove foreward it was making pop /sputtering ---- then i came home from work and attempted starting it which it started up and idled fine but when giving it gas it stalled ----- any ideas ----- about 2yrs ago i replaced the complete intake gaskets with the 2 seperate redesigned 1's cuz i had po17x lean codes ,,,, i have a fairly new iac ,,,, i have had this truck since 07 and havent changed plugs,wires,fuel filter ,,,,, truck has had a engine light on and code is p1443 manufacture control ,,,which has to do with evap purge flow ,,,, any help will be appreciated thanks

 

let's sit down and think about this ....

- hard starts cold
- restarted a couple times but only at full throttle
- evap purge code

this really sounds like a rich fuel condition. the tell tale is starting at WOT. WOT is flood clear mode. more than 80% throttle at key on and most vehicles cut injector operation in an attempt to clear cylinders, helping a start.

there are a couple ways i would go about this as preliminary checks ...

1. check fuel pressure. does it build to spec with key on? does it hold pressure key off (no more than 5 psi drop in 60 seconds)? what is the pressure running?
- if it has been a while since your last oil change, is your crankcase level good? is the oil condition "light", almost like it has been washed down with fuel?

the reason we start here is to test a couple things
- is the fuel pump giving us enough pressure to start and run this thing?
- is the pump holding pressure key off? if not, why? is it draining back into the tank, screwing up at the regulator and dumping fuel into the vacuum line, or leaking trough the injector into the cylinder? (****sorry but i can't remember the fuel regulator system on these things. i'm assuming a mechanical return style system with the regulator by the fuel rail)


the other issue/possibility is the evap code ... your evap air supply from the purge solenoid is basically 100% vapourized hycrocarbons. it's pure fuel. it is an operating strategy of the evap system to not operate at idle. (purge events typically happen only at cruise).

if the purge solenoid is remaining on then your engine could be drawing raw vapourized fuel. this could give an excessively rich condition which would call for a hard start throttle closed, but maybe a possibility of starting at WOT due to more oxygen coming in and leaning out the mixture.

- check operation of the EVAP purge solenoid. if tests lead you to suspect it, temporarily block it off from the intake and attempt cold start. that should help narrow that one down.


good luck. hard to diag without seeing things, but i hope this points you in the right direction