Still having the same trouble with my engine that I just can’t figure out after reading and researching a vast amount of SBC and third gen related websites.

Engine in question is an '88 305tbi. All was well until the engine started surging upon a cold start. I discovered and replaced a torn vacuum line from the throttle body to a T junction near the passenger side of the distributor.

I tried to start it yesterday and the same issue occurred: engine would try to idle, then surge a little to nearly dying, and would rev again. I can keep it going, but only if I’m sitting in the seat or under the hood to keep an eye on it and manipulate the fuel delivery. Once the engine is warmed up (about 2-5 minutes) it’ll idle and run like nothing was ever wrong. For kicks, I also wanted to see if the problem happened in gear when cold, it does. If the engine is started warm after being run (like at a gas pump or grocery store visit) it has no problem starting and idling correctly.

So far I have:
Replaced all questionable vacuum lines (which was almost all of them)
Replaced spark plugs (they were due) and inspected cap and rotor for any issues. There are none.
Replaced the EGR valve. It operates correctly.
Replaced the IACV this morning. Same problem occurred. Instructions said to run at 40mph for a short period of time to "learn" and "reset" the valve. I did this for 5-6 miles, uninterrupted. No change.

Seems like I still have a vacuum leak somewhere (and that I've wasted ~$100that could have bought powerball tickets ).

I read that I should pull and plug the PCV valve and breather. Then check for vacuum at the dipstick. If vacuum occurs there then it means the intake gasket is leaking and sucking air from the crankcase.

Other than the above, does anyone have any other suggestions?

 

Are you getting heat from the ext manifolds? thermac?

 

Possibly CTS=Coolant temperature sensor. May be reading wrong when cold. Then when it gets hot it reads correctly to tell computer what to do.

 

You're talking about the one near the thermostat, not the coolant fan switch in the block, right?

 

This is a coolant temp sensor. You need a volt meter that can test ohms to test it.

 

Resolved.

Took a trip to Autozone this morning, bought a CTS, a TB base gasket, and intake manifold gaskets; just in case the easiest part to remove and re-install wasn't the issue.

Replaced, disconnected the battery for a few. Reconnected and BICKITY BAM, bitch starts right up.

Seemed odd to me, but figured it could be stuck in an open loop and the PCM interprets the engine as warm all the time- hence why it runs well once warmed up.