Constant backfire on deceleration 88 chevy 4.3 V 6

chevy pickup 2wd. (C) gen4 truck, pick up not the Suburban C1500
no engine told and is engine question , no VIN told (has engine code)
4 engine , 3 gas, 1 diesel. gas 4.3,5.0-and 5.7 and D6.5

OK 4.3 told
LOST YOUR SCAN TOOL>? USA answer me, 1998 is OBD2 here.
Barrow ,rent ,buy or get any shop or even car stores to scan it?
that is called misfiring and the can too for sure reports on that,
its not scanning first the reason , we don;'t know./
some car must be driving hard, to get a CEL even 3 times drive cycles. or if in CANADA THEIR Silly OBD2 masks many codes failing , as seen scanned,
a bad FPR can show good fuel pressure then fail up hills or more load put on the engine, (it fails to regulate at all times)
my answers are generic, due top no engine or vin told.
if I had replaced all that, id have stopped
and scanned it, then a compression test now
and make sure all spark plug tips look no, not green with antifreeze or carbon or OIL soaked and then compression test. is really first
no bad engine runs right, for sure below 150psi compression. (gas)
99% of all posts here never tell that engine or scan the PCM./
making answers pure ASE day 1, answer generic.
engine good, ALL CYLspark good , ALLfuelNG good.1,2,3 (pure physics really)
sad is what if EFI OBD2 told you what is failing?
CYLINDER 6 (WEAK COMBUSTION) DTC CODE
say P0306 fails, and spark plug 3 is green COATED (AF50%)
OR SOAKED IN OIL AND COMPRESSION IS 50PSI OR ZERO
SAD TO MISS THAT, NO?
SCAN IT.

U need to have the timing checked to be sure it is not the problem.

Is the check engine light on, and have you checked base fuel pressure with a gauge ?

Have you checked the fuel pressure under a load, low pressure will cause these symptoms. The test port is on the top of the engine in the fuel supply rail to the fuel injectors, the fuel pressure test port looks like a large tire fill valve. You will need a fuel pressure test gauge to do this test (about $20), the pressure must be watched while you accelerate, it should never go down on hard acceleration just up about 6-8 PSI

For this types of problem,there are few help inks to troubleshoot the problem.Click the link below to go through the troubleshooting procedure to resolve the issues :----Idles rough and quits when gas pedal is pressed less? http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html-----------van idles rough? http://howtobyme.blogspot.in/2012/01/2004-ford-freestar-van-idles-rough.html
--------------runs lean and idles rough? http://technoanswers.blogspot.in/2012/02/ford-runs-lean-and-idles-rough.html
-----------Car still runs Rough after tune up? http://howtobyme.blogspot.com/2011/12/car-still-runs-rough-after-tune-up.html
------------Idle flair is noticed on car? Rough idle? car will not idle? Erratic idle speed? http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html
----------High rpm in neutral? Inconsistant high RPM in neutral? http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html
------------Engine Backfires? http://technoanswers.blogspot.in/2012/02/jeep-backfires.html----------- Nissan stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

-----------
Nissan Pathfinder Backfires? http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
---------How to adjust rpm? http://schematicsdiagram.blogspot.com/2011/12/how-to-adjust-rpm-on-2009-dodge-charger.html
------------Engine cuts out at 3000 RPM? http://schematicsdiagram.blogspot.com/2011/12/engine-cuts-out-at-3000-rpm.html
----------This will help.Thanks.

Please elaborate on "runs rough"
Is it slipping gears.... hesitating on acceleration... missing... smoking... backfiring?

Thanks!!

IN your distributer under the rotor is a magnet and a pickup coil (the magnet is known as a pole piece) check your pickup coil for corrsion (green in color) and the module and also check pole piece for cracks in the magnet where the rivets hold it together. sometimes oil wicks up around the distributer shaft because of housing wear or the pieces just wear out over time.

get the egr valve checked, place to start

I had the same problem, thinking it was bad gas, or bad wires, or even a clogged fuel filter, had the engine checked out by a reputable gear head. A head bolt broke, then a intake lobe from cylinder #4 spun round thus causing your car to constantly backfire, also check to see if your head gaskets aren't blown (water-n-oil), all these were found once the engine was disassembled. Good luck trying to find a good used 3.4

bad dis cap or rotor maby a bad plug wire or valve sticking or out of adjusment