Cold Start--Barely Runs

[RareCJ8]

New to the forum. Hello!

4.6 in my CJ. Cannot get cold starts to be friendly. Cranks over right away and very rough idle and will die unless feather some throttle. About 45 seconds to minute, smothes out. But get in to drive and another issue. Try to accelerate and it stumbles, no power and getting a massive 'backfire' from under the hood. Can barely limp out of driveway. So far the solution is to pull over and let it idle for 5 minutes and increase RPMS and go. Once its all warmed up runs like a boss. I'm no mechanic but this is the best I can explain. Relocated the intake sensor to the air intake tube. replaced coolant temp sensor. slight pinging on long uphill freeway grades.

Drive for how ever long and park for more than like an hour and it happens again. On trail rides hesitant to turn it off.

Basic specs:
1) A Competition Cams 252 grind
2) 8.7:1 compression ratio; hypereutectic pistons and moly rings 24lb ford injectors

getting frustrating-- cannot just get in and go.

searched and found one the thread but do not see any solutions. ideas?

thanks

[SilverXJ]

#1 Reindex your distributor http://www.angelfire.com/my/fan/dist_index.html

What fuel injection system are you using?

What is your fuel pressure?

[RareCJ8]

thought the distro was good. will look again. using the mopar efi kit. IIRC, maxes out around 42 psi.

[SilverXJ]

And when you checked it it was around 42 psi?

[RareCJ8]

And when you checked it it was around 42 psi?

yes

what is odd, after the rebuild it ran great fo about 4 months then here lately this stumble, sputter, etc started out of nowhere

[Cheromaniac]

Pull the distributor cap and try turning the rotor in either direction. If there's a lot of slop, it's a sign of a worn distributor drive gear.

[RareCJ8]

will do. all parts are new and only have about 700 miles on new engine. not sure how it can wear so fast. oddly, once its fully warmed up it runs fantastic.

[SilverXJ]

42 is an odd number. Earlier stock systems were 39 psi, later systems were 49+ psi. Where the symptoms happening while you checked it?

Does the mopar kit have the CPS on the front of the engine? If so, could it have moved or spaced out too much or just plain bad?

[racing89]

hmm. Could it be possible that it runs well in closed loop only ? Does the mopar efi utilize a heated o2 ? if so, could the heater element be shorted out ? Anyone know if there are open loop functions that change when closed loop is established ? ( eg. map or tps ) . If its not loading up and flooding when its cold, we can assume its too lean. You changed the cts, is the ecm getting signal ?