Replacing throttle body inj.

I agree with the others on the TBI. Keep it and fix it, itsa good system, way better than any carb, in this application.

Some very good suggestions above.

One other thing (or 2 or 3!)

EGR. Exhaust gas recrculation. Round can with some vacuum hoses bolted to the manifold behind the TBI. The can can fail, or the valve under it get gunked up and stuck, or any of those nyriad vacuum hoses get disconnected or holy. EGR is normally on at cruise, pretty much off at idle or accellerating. Being on when not supposed to be makes an engine run really bad.

That myriad of vacuum hoses. They are old, and may be collapsed or fallen of or haave tiny hidden cracks, any or all of which can effect these engines.

Spark Plug Wires. Big block chevy's love to eat plug wires. They get burned, or tiny holes. First step would be to drive the coach at night with the dog house cover off, looking for a light show. Or just replace them, and the plugs.

I've got a carb on my "90" Stay with the TBI.

The TBI is one of the most reliable systems on the planet. Have it checked out!

IAC's are the devils creation!
If when you come to a stop it sometimes idles OK and then other times it just wants to (or does) die, that's a classic sign of a sick IAC.
If you are having those kinds of problems then the IAC is a good shotgun.

Another thing you can do to make the IAC work for a while sometimes: turn the AC on and off about a dozen times making sure that the compressor kicks in each time. This will force the IAC to slam back and forth and will often free it up for a while.

It might have nothing to do with the TBI. There are oxygen sensors and other sensors that affect the operation of the engine. You really do need to find the real problem rather than to throw money at something that will not work as well on an engine with electronic controls. Have you hooked up a scan gauge to see what is out of tolerance?

Big mistake. Stone age or computer age IMO. Find out what is wrong with it. Start with the fuel pressure, if it's ok, then do a volume test. You must have both. Check all your vacuum hoses for cracking and deterioration.

All it probably needs is a good cleaning... How many miles is on it?..

TBI is a lot better than a carb, get a rebuilt TBI or rebuild it yourself, you can also buy a performance TBI from Holley

enblethen wrote:
I would not change.
Have the TBI unit cleaned. It could have problem with the idle air control valve. The AIC acts something like a choke. It is located on the right side of the TBI unit. Held in place by two small screws. Careful they break easy. The air passage can get clogged with carbon causing idle to be erratic. It operates off the ECM with input from the temperature sensor for the ECM and not the one for the gauge.
Another thing to check is the fuel pressure regulator to insure the proper pressure is getting to the TBI. It can be high causing surging or too low to create stalling.
When does the rig surge?
When does it stall?

X2, I would find the problem and fix rather than go with a carburetor. It could be something very simple. My DD car was doing what yours is doing and it was only the TPS. JMO

I would not change.
Have the TBI unit cleaned. It could have problem with the idle air control valve. The AIC acts something like a choke. It is located on the right side of the TBI unit. Held in place by two small screws. Careful they break easy. The air passage can get clogged with carbon causing idle to be erratic. It operates off the ECM with input from the temperature sensor for the ECM and not the one for the gauge.
Another thing to check is the fuel pressure regulator to insure the proper pressure is getting to the TBI. It can be high causing surging or too low to create stalling.
When does the rig surge?
When does it stall?