Good evening,

Recently picked up an 89 f150 4.9l I6. 120k miles. The day I drove it home, all fluids checked and passed visual inspection and levels. Ran home no problems. Recently did a 'tune up' cap and rotor, ngk plug wires, FoMoCo spark plugs *copper core and gapped to spec* new fuel filter. Oil change 10w30 and mobil 1 filter. Transmission fluid still clear and red. Coolant nice a vibrant green.
Old cap had a bit of corrosion, but after the tune up engine seemed to be running a bit better.

The following day I went to go take the truck out and upon initial start the engine began to seem to surge/rough idle. I checked on vacuum lines per diagrams and video on YouTube, and wasnt able to find a leaking hose, also have a vacuum gauge to test at various locations..is there a spec for vacuum per hose? Checked fuel pressure Key on engine off. 43~psi and about 41 while at idle. Gas is clean. Than I began to replace each sensor one at a time, if it didn't improve i swapped the old one back onto the engine. I've heard new sensors aren't as great as OEM, so leaving the original is my goal if possible.

Haven't cleaned the IAC but swapped a new one on but did not solve my issue. Same with TPS. Put a new Air Temp sensor in, old one was fouled. Im leaning towards a failing EGR sensor? Or one of the 3 solenoids.

Any help is much appreciated.

 

Welcome to FTE
It looks like you have done all the right things so far and then some as most start throwing part at it and leave the new parts installed.
Thing is what if you got a new bad part to replace a bad part? No real way to know but just had to say

Have you checked for codes yet?

I would pull the EGR and make a block off plate from a tin can, to block the port for "testing" (wink wink) this way you know this will not cause a problem (for now wink) as a leaking EGR and make it run ruff like a vacuum leak.
I would also like to know what the compression is on the motor to rule a dead hole out.
Motor cold spray a little water on the exhaust manifolds close to the head. Start the motor and let it run a little keeping an eye on the manifolds and then shut it off.
As the manifold heats up the water should evaporate and they all should "dry" at the same time. A hole that is not firing even a little less will stay wet longer and a closer look into why.
You can also pull 1 plug wire at a time at idle and see if there is a change in the idle. No change that hole is not helping and could be why it run ruff.

I dont have anything else sorry.
Dave ----

 

I would definitely do the things that Dave mentioned. Reading the codes is a must. One thing I always check on these just because it’s easy is when you turn the key to the on position, not running, as in before you start it does the check engine light illuminate? If it does then while the engine is cranking does it go out while cranking? In both cases it should.