Please Help!!! having 87 pickup problems

[bigdaddycaddy39]

I have an 87 chevy 3/4 ton 305/th400 fuel injected pickup 2wd and I am about to pull my hair out. The trans pump went out and the truck sat for a year or so and I finally repaired it. The pickup ran great before it was parked but when i got the trans back in and tried to start the truck the fuel pump had gone bad so i replaced it and started it up and the engine ran terrible. I put fresh gas in, changed the plugs, new battery, new dist. cap and rotor button(old one was burnt up), rebuilt the injectors(leaking after the engine was shut off) computer was throwing a few codes so i replaced the manifold coolant temp sensor, o2 sensor and map sensor. With all of this done the engine is finally running smooth at idle but sputters in drive at low speeds until you build up a little speed then runs ok with just a slight surge at highway speed. The truck never smoked before but now it puffs smoke at idle and blows out quite a bit when you rev it up..bluish grey color...not black and if you mat the gas in drive the truck stumbles..backfires...and dies. the only code the computer has is a high voltage o2 sensor code 43 i believe.I just discovered the rubber seal on top of the sending unit/gas tank is leaking. Can the tank be losing fuel pressure and maybe causing the computer to over compensate fuel and maybe flooding the truck? Any help would be greatly apreciated.

[GM-power]

Bluish-gray generally indicates oil burning. For sitting for one year the gaskets etc... in the engine may be kaputs.
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[bigdaddycaddy39]

would a broken ring or blown intake gasket cause the truck to stumble on aceleration and backfire when i stomp the gas from a dead stop? Also the truck will randomly stop smoking at idle and one time someone told me to unplug the egr vaccum line, plug it, and drive the truck to see if the egr was bad and when i tried it the truck did not smoke for at least 5-7 minutes and then out of the blue started smoking again???? Maybe it is haunted LOL!!!

[bigdaddycaddy39]

I did run a compression test and all 8 cylinders were dead on 150psi and all pumped up evenly so that should rule out several internal problems? None of the spark plugs were unusually oily or ashy...just black and a little sooty...all of them were about the same..............if a gasket were bad and letting oil in the cylinder that particular plug or plugs should be oily? Im just stumped on this one!!!

[bigdaddycaddy39]

Also i noticed when i unpluged the timing wire so i could check timing the truck idled down and started running like crap and died out????

[rfmaster]

Originally Posted by bigdaddycaddy39

Also i noticed when i unpluged the timing wire so i could check timing the truck idled down and started running like crap and died out????

That's called set EST connector. With this one wire connector open ECM does NOT provide any timing control and SA timing is fixed (usually 0 deg). This will explain why engine is dying when you place it in drive - you do not have timing set correctly. Set EST connector is only used to set distributor base timing at idle (park or neutral). Stock engine will idle at very low RPM ~ 550. LO5 truck base timing is 0 deg BTDC. Once you set the timing, shut engine down, reconnect set EST connector, clear ECM codes by disconnecting battery for 30 seconds. Upon engine restart timing should be bouncing between 16 to 20 deg and idle speed around 600 to 625 RPM. It should not be stalling unless you have lost couple of cylinders and engine is misfiring badly.

//RF

[BIG DADDYS 84]

check for vaccum leaks,and under throttle body,thats common. stumble and surge are signs. just spray arround base plate to see