1988 350 TBI Uneven Idle?

[Valdfur]

Picked up a 1988 K3500 last year with what I believe to be a TBI 350. Runs great and has under 100k kilometres on it, but at idle it bogs down to a near stall before returning to normal idle speed. Any ideas on what's wrong?
(It's got an SM-465 in it if that helps)

 

[movietvet]

Welcome to the forum from Oregon.

Any running problems on an unknown engine history, I start with basics. Compression test with all plugs removed and a fuel pressure test. An inspection of parts is also needed. IAC needs to be looked at. Look at plugs. Check for clogged fuel filter. Check the cap and rotor condition......etc. Any CEL?

 

[Valdfur]

Thanks!
That makes good sense, I'll check over the engine soon, as for the running condition, this problem only seems to occur when it's idling. I'm not sure if the dash lights work or not, but the check engine isn't on