1987 chevy truck 350 tbi stumbles sometime will die right off idle. effects trans lockup and jolts truck. put three tps sensors in it and rebuilt throttle body. code 12 and 45 are present still have no clue of why it floods right off idle but runs fine at any other throttle angle#

SOURCE: Rough idel

OK, Im sensing many issues here. I will list the most important check points below that you will need to inspect thoroughly. I recommend running a code check as well if possible. the check points are listed as follows..

Check Points---

1. Inspect the EGR Valve-- A Improperly Functioning or Faulty EGR Valve will contribute to misfiring and instant death of the engine.
2. Inspect all Fuel injectors-- Dirty or Worn Fuel Injectors can cause rough idles as well. inspect accordingly.
3. Inspect the Idle Air Control Valve-- Damaged, Loose, or Faulty Idle Air Control Valves will cause rough idle.
4. Inspect the idle speed actuator-- It could be loose or faulty.
5. Check the throttle position sensor. this is a know problem spot when the idle is erratic or unstable.
6. Make sure you are running a clean air filter as well. this is a simple check that may fix your idle issue as well.
7. Inspect the PCV Valve-- This device may be clogged or damages. make sure the hose is not bent.
8. If there is a Carb present, i would run a thorough check on all lines and choke assembly as well.
9. Inspect the valve assembly for Burned, Worn, or Sticking Exhaust Valves. this can cause back firing and rough idle as well.
10. I also recommend checking the timing chain for slippage or worn timing gears as well. this can cause your symptoms.
11. INspect the fuel pump for faults.
12. If you have run through the above list to this point and still have not seen anything unusual, i will now recommend pulling the cam to check for worn Camshaft Lobes. this will screw up valve timing and affect the engines idle greatly.
13. if a distributor is present, i would check the ignition points for worn or incorrectly set points.

This concludes the check list. you will find the problem in one or all of the areas stated above.

Please rate and god bless:)

SOURCE: 87 chevy truck with TBI idles too fast

Spray the intake with carb cleaner to find the vacuum leak. Check where the EGR mounts and the throttle body gasket sense you had both off.

SOURCE: 93 Chevy Sub new rebuilt motor and trans, new fuel

Its possible you have some heavy vacuum leaks? I'd inspect every thing well to identify an open line or poor seal drawing air in.
I hope this may have helped,
Tom

SOURCE: Chevy 1988 truck 5.0

idl air control (IAC),may be bad,also,check the EGR valve,and all vacuum lines going and coming from the throttle body. yu can test the EGR,just try pushing the diaphram by hand from beneath. if you can move it easily its good,if its hard,or doesnt move,ot needs repaced. also a pcv valve and air filter are good ideas,considering you have replaced 80% of the emission system already.

SOURCE: I have a 1990 suburban 5.7 tbi is puring fuel

Coils ever get replaced? They create all the spark, if not enough spark no combustion so it will act flooded.