94 4.0L runs rough when first started


alabamafrog

15+ Year Member

Joined
Feb 22, 2010
Messages
37
Points
3,101
City
Decatur Al
Vehicle Year
1994
Transmission
Manual
My little 94 Ranger 4.0L with around 220,000 is getting to where it runs rough when first started, especially when the engine is hot. It even dies sometimes. The idle seems kinda erratic too. After a minute or two it will usually settle out and run and drive just fine. It will also usually act right when returning to idle after driving. The idle does seem a little high and occasionally under full throttle it feels like it might miss a lick or two. Still gets consistent 21 mpg, last fill up was 18 mpg but I think that I forgot to trip the odometer or something.
Where should I start looking?
 
As far as the hot engine rough start, its most likely that the hot engine is "vaporizing", for a lack of better terms, the fuel in the fuel rail. Theres a thread somewhere around here that explains it thoroughly. The updated fuel rail spacers in the 95+ models were to help this.
 
I’ve had this thing since new and I don’t remember it acting like this until the last few years. I figured it was something wearing out or getting dirty.
 
a malfunctioning IAC can act similar since in effect its the choke for the engine. once the engine has warmed up some its not needed.
 

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