Why does my astro with vortec engine start hard when hot, and surges along wit misfire, but runs good after starting/

surges(no engine told)
hot, and cold engine
any gear, and at idle too. and PARK.?
rpm varies .
surges at cruise,or WOT, wide open throttle?
misfires. ? violent, felt.
scan the PCM when it surges?
lots of causes even cracked brake booster and crazy vacuum leak, now.
and more lots more,

It could be a fuel or compression problem that is causing your misfire. To eliminate a clogged injector as a possible cause, you can swap injectors between cylinders and see if the fault follows the injector in question. Or it could be a fouled or incorrectly gapped spark plug causing the misfire. Do a compression check with the engine warm, preferably right after a misfire event.

WHAT COUNTY???????????????????????????????????
hot engine, cold or both?/// a key question
WHAT ENGINE: ( usa list , ONLY)
2.2 L F22B I4
2.2 L F22B6 I4
2.3 L F23A I4 2.3 L F23A7 I4
the fsm covers this. hose thing.... all hose can be followed,
unless its axle vents on 4wd cars. (they go no where, special)
is surging the only symtom.?
no engine stalls.?
lack of power in any gear or hills.
no misfiring?
no flooding.?
starts easy/?

ok what is surge, that it really is idle controls bad or out of comtrol
1: idle controls bad. (isc dead?)
2: or engine is running way too lean, and ISC cant keep a grip on idle.

easy huh?
and #3 misfiring so bad the idle controls fail.
are all fuses good?
is the CEL lamp glowing , then goes out running engine.
no , the scan it. or do the flash DTC codes trick.

a good tech ,first finds out if the engine holds closed loop status
hot. at idle, if not, he fixes that first.
as he/she knows that idle is the last thing to work right, in EFI.

one other way to get surge is air leaks (aka. vacuum leaks)
if the engine (unsaid option) is MAP based, it will race fast
with any vacuum leak, and it dont take much of a leak
to make the ISC idle controller go nuts.

so repost , hot/cold both questions
and actual RPM numbers. we need numbers
is the dash Tachometer missing. ????
and what engines in car.

all lean engines surge.
all ISC systems can surge if out of control , not all do this. just 1/2
if the ISC surges, it means its trying hard to gain back control.
this is called a software servo loop.
The ECU is programmed to hold rpm near say 800 RPM hot.
and is very digressive in that role.
I have a 91 car that will surge, with any vacuum leaks.
(by design) depends on which engine.

giving year make and model helps the professionals be able to identify your problem this is such a vauge description of problem that we can give you wrong info very easy and costing you a lot of money..

Sounds like fuel problem to me?? Have you changed the fuel filter ?

Here is some ideas coil pack, out of time, new wires, dist.cap, throttle position sensor, idle control valve, or take you air hose from air filter and check the wire screen inside you mass air flow sensor and make sure it's not plugged. That year of truck can be checked with a obd scan free at Auto Zone or Advance Auto Parts.

the fuel pressure should be 60-66psi so i would start by changing the fuel pressure regulater to get pressure were it should be. to much pressure will bleed past the injector and cause the car to run as you described

tsb remove dist cap ,clean out breather holes i replaced cap and rotor at the same time. chevy has the problem with the 4.3l astro,s and blazer i have both.fixed the problem when buying the cap and rotor the directions inside will also tell you how to fix

these vans where kind off know for haveing problems with there dist. check the dist cap for cracks, check the coil wire also. what has happened is that mosture is getting in some where and probley the cap is at fault. when s the last time the vech has had a decent tune/up cap rotor plugs wires . replace the cap and rotor and coil wire, should solve your problem . but i would recommend looking at the other tune /up parts good luck kdc744

your battery is about to die....