Chevy V8, 5.3L, 4wd, engine missing between 48 and

Ronald,

Give them a hollar....

Spec sheet says idle control...full speed.

https://www.electricgeneratorsdirect.com/manuals/5626spec.pdf

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Have it check for DTC'S - diagnostic trouble codes . If the check engine light starts flashing , park it . The flashing check engine light is telling you there is a catalytic converter damaging miss fire happening . An they can be damaged very easy .

Should be on or near the fuel injector supply rail.

is the check engine light on? have you ever serviced the injectors? if not try that first because there are many things that give the symptoms you spoke of. but this is the cheapest.
vbninja E.A.P

i suggest taking it to autozone or similar parts store and haveing the codes checked.

If the engine seems to run fine over 1450 RPM maybe there is a vacuum hose leaking or EGR valve is slightly stuck open. Any help from the OBD II trouble codes? Or is there simply no MIL and no stored information in the OBD II computer read at the local parts store through the connector by the drivers knee?

when you turn on the a/c the ecm increases engine fuel to compensate for extra load could possibly be a vacuum leak

is your check engine light on? check your O2 sensors

An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The car computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air.
An IAC motor is highly susceptible to carbon and coking build up; if an IAC goes too long without cleaning it can cause stalling and poor idle quality. Some cars are designed with a large vacuum transfer hose that connects the intake manifold to the IAC (idle air control) motor. If a broken or dilapidated these vacuum lines can cause the engine to lose vacuum which will allow the engine to run rough and die. 
Inspect all engine and accessory vacuum lines to look for missing, torn or dilapidated lines and replace as needed. To check the IAC motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the IAC should move in or out. 
If the IAC motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the IAC motor is removed clean (use aerosol carburetor cleaner) the passages the IAC uses to control idle air speed.

Good luck and hope this helps

dude its normal for first start or cold start that the idle is ok but it must high than normal... its normal because the engine is warming up it self... when it gets warm, the idle speed will return normal idle... your engine is 1200cc, it has not much HP for a great load... and i know its a carburatored engine and its an old engine, your head lyt and a/c fan and aux fan and all the electrical system on your car, uses the HP of you engine and its a lot of load to the alternator driven by the engine to generate an electricity they need and thats why the engine rpm speed lowering down to dead and its shake. thats why when you use your lyts or all electrical, you engine is weakening... the best remede is adjusting you idle speed... its located behind the carburator.. its a small black knob.. just make a twist each eighter way and you'll find out if your idle rpm speed ts incresing or decresing.. just increase it and try opening your lyts and other electrical, if its still shaking then adjust it a little more