92 F-150 5.0 rough idle
 

My problem started 4 days ago. My truck was starting fine (didn’t idle rough) and the next morning it wouldn't start. I tried five or six times to start it and no luck. Normally it will start up first try even in neg temps. The next day I disconnected the wire harness and plug wire from the ignition coil and the wire harness from the ignition switch. Reset the harnesses and the truck starts up first try and now the starter wouldn't disengage. Had the starter rebuilt and reinstalled it back on the truck and it started but had a hard time keeping it started. I had to push on the accelerator for a few minutes then it was idling rough. I let it set a few hours and went back out and started it back up and it started first time and went to high idle till it warmed up then it idled rough. You can set in the cab and feel it shaking and you can watch the engine rock. Also when I shift from park into gear it drops low enough like it is going to stop running for a few seconds. You can see a considerable drop in batt voltage when this happens. Not sure what the problem could be since it went from running fine and 8 hours later it is falling apart. Any ideas will be greatly appreciated. Thank you.

Start with the free/cheap stuff.
#1- disconnect the battery for a few minutes. reconnect and see if it helped.
#2- clean the IAC valve.
#3- check TPS. should be 97-99v at idle.
If none of this helps, get the codes checked.

1) Don't disconnect the battery before you check for codes - it only takes a minute with a paperclip.
2) A bad IAC won't cause intermittent starting, but if it's bad enough to need cleaning, it needs replacing.
3) Checking the TPS is good, but I'd be more interested to know the fuel pressure. I'm betting it's low. Click my signature link & look in the EFI Fuel Pump album.

Thank you for your help. The truck started running better the next day. I plan on changing out the rotor and cap and a few other components just to give thtruck a good tune up. The check engine light still comes on and goes off randomly. Tried to get it read but the machine was broke. Again thank you for your help.

You don't need a machine to pull codes. Just a paperclip & the link in my previous post.