after rebuilding my efi 351w it seemed to run rough. got any sugestions??

 

Engine roughness after removal could be caused by a simple vacuum line disconnected or perhaps a poor electrical connection.

Normal CPU learning strategy is irratic engine running conditions more so than roughness. Recheck fireing order, vacuum and electrical connections. Am also remembering some of the 351W engine using a 5/8 socket to run down valve lash meant adjustable lifters, if a 9/19 socket is the size, these are not adjustable, just run down tight.

 

how would i know if my vacum lines are in the right place? It starts fine but when it warms up and tries to idle it surges from 1000rpm to 2000rpm repeditively until i make it stop by giving it throtle until it smoothes out then i let off and it will idle smooth then.

 

so this only happens once? meaning after you smooth it out it will run and idle fine for the rest of the day?

From the information I have I would start by checking all the vacuum lines and electrical connections, check wires for shorted together or to the chassis etc... Try spraying some WD40 or something flammable around the intake gaskets etc to aid in checking for leaks. I would also maybe take a look at the Idle control valve on the throttle body. Not 100% familiar with that engine but pretty sure they have idle control.

Its possible with a rebuild that something was connected wrong or not torqued down properly causing mixed signals or leaks. Also possible wires or connectors were damaged during the process. Just recheck everything for insurance.

 

What you have sounds like "lean surge" and if it settles down after you play with the throttle then you must have a engine management valve of some sort sticking causing a lean condition. I don't know much about the throttle position sensor system your truck uses, My '95 has a Mass Air Sensor. I'll would bet a good tune shop could find the problem real fast.

 

Thanks for all the info guys. I realy apreciate it.