Engine/Transmission (1994 - 1998) Wierd Miss

[Stixx]

My friend has a 94 auto with 120k on it, just lately when he starts it up it has a wierd miss. It will idle fine for 20-30 secs then miss and stumble and slight black smoke. It will miss for about 5-10 secs then idle normal again. It repeats this cycle untill he drives it or holds it at higher rpm.



He put a new lift pump on it about 3000 miles ago.

He has an air leak that he hasnt found whats causing it yet. At normal operating temp in neutral he can hit WOT and about 1800-2000 rmp it stumbles and miss's (lots of white smoke)



We think its the fuel heater sucking air. We plan on looking at it tomorrow.



Would this air leak cause it to idle funny like I explained above?

When it warms up it wont idle like that only when its cold.

 

[bmoeller]

With that may miles on it, have the valves been adjusted? It helped mine. Mine still sounds like a cylinder is still a little off, gonna check my fuel injection nozzles next.

 

[LSMITH]

Check the overflow valve too.

 

[Blakers]

Originally posted by Stixx

At normal operating temp in neutral he can hit WOT and about 1800-2000 rmp it stumbles and miss's (lots of white smoke)

This is the nature of some of these engines. Mine does it too. I've been told that it is pretty common and nothing wrong. It's caused by too much fuel and not enough boost with no load. Under load it should be fine.

 

[Stixx]

He had the valves adjusted when he put in the new lift pump.



Could this life pump be bad?

Under a load (driving) it runs fine.