'94 3.0 Auto cold weather misfire

[Stankard757]

Picked up my 94 with a 3.0 this past summer had to replaced a few sensors and it ran great. A little over a week ago the temperature here in VA hit the 30s overnight (work mid shift) Got off and started the truck to go home. Truck started right up without hesitation, but once idling there was a loud rattling and when I tapped the gas the engine would stumble. After a few minutes the rattling and stumble goes away and it runs as good as before no problems.

The oil is good and clear, same with the coolant. No obvious leaks, No smoke except for when it stumbles, but that clears up when the rattling/stumble stops. No weird smells and no codes. And the compression tested good when I bought it. What's confusing me is it only occurs when the temperature drops, the colder it is the worst it gets. Hasn't done it on warmer days and not if parked for a short amount of time ie ... couple of hours. Kinda sounds like the valves are slapping which is why I thought fuel/spark systems.

My plan of attack is to start with checking the "spark" then move onto the "fuel". Unless some of you fine individuals have come across this and can point me in the right direction.

Thanks
Mike

Ps.
Almost forgot this is not the original motor. It was replaced by a previous owner I have no history on it.

 

[franklin2]

How many miles on the engine and what type of oil are you running? On a worn engine it may take a little bit for the lifters to adjust in colder weather. The lifters may be a little sticky also if there is a lot of sludge build up in the engine. A can of Rislone in the oil will usually fix any lifter problems.

 

[Stankard757]

Truck has about 136, 000, engine is unknown was replaced 2 previous owners ago all the kid I bought it from knew was it was supposedly low mileage. Had the engine checked and fluids changed by a local shop before I handed over $$. So probably a generic stock weight oil.

I'll pick up some Rislone and give it a shot. Finger crossed

Thanks

 

[bills4065]

It sounds like a cold engine only issue. I would check my engine coolant temp sensor and associated wiring to make sure sensor is operating properly.