S10 running problem

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11-22-2011, 10:08 PM
Memphis

S10 running problem

96 S-10 4.3L vin X 5 speed. New injector, new tune-up parts (cap, rotor, wires , plugs), newer fuel pump, new distributor with module. Compression is fine, fuel pressure runs around 50 (calls for 60-66) I ran a stand alone fuel supply bypassing the pump and ran it at 65 psi with no change. Scanner shows multiple cylinder misfires with 20000 plus on cylinders 1 through 3, nothing on 4 through 6. Cat is hollow so O/2 in the rear shows no activity. Truck has lack of power and misfires (popping noise) off idle and under load. Not consistent enough to be an engine noise. Thought maybe t-chain jumped but with little to no misfires on 3 cylinders...same thought with ign coil. Internal issue should show with compression unless maybe a worn cam? Maybe faulty cap? I dont know which way to look anymore...
11-23-2011, 07:31 AM
WickedSix

ignition module? bad hall effect sensor in distributor?

when did it last run right? miles? vacuum leaks?
11-23-2011, 08:45 AM
PonyKiller87

Did you use a GM distributor cap? The Vortec 4.3, 5.0 5.7 and 7.4 are very picky about the distributors. A lot of the aftermarket ones that you get at auto zone are aluminum posts vs the GM brass posts. Also check the shaft play in the distributor, if you grab the rotor and can move it side to side its junk. If you need a new one look on ebay, there are companies selling the aluminum bodied distributors with the brass point caps for about $70 which is far less than the stocker and a ton better.
11-23-2011, 10:07 AM
BR3W CITY

I've had 4 of these, between s10's, Blazers etc. Twice I have had to return dist caps to Napa because they were made almost 1 position entirely off. Never sat clocked right, even when it looked on correctly. When I exchanged it, the part looked the same but was different when you look at the underside.
11-23-2011, 10:28 AM
BAD LS1

Tested compression or leakdown on the offending cylinders? Not that it has a bent/broken pushrod being a 5 spd and all... Maybe broken valve spring worst case? If all else checks yeah, the above statements about caps are good possibilties. Un-plug MAF sensor too and let it run in SD and see if that helps to smooth anything out. If it gets noticeably better, there is an airleak after the fact it doesnt like. How do the long term fuel trims look? Extreme + or -?
11-23-2011, 06:13 PM
Memphis

God damn thing....put another new...and obviously better...cap and the damn thing runs great. Thanks everyone for the help and advice!
11-23-2011, 09:06 PM
BR3W CITY

^ the chevy shitcap strikes again. Glad it worked.
11-24-2011, 11:38 AM
Memphis

Me too! lol. Thanks for all the input.
11-25-2011, 11:36 PM
Nickerz

Quote:

Originally Posted by PonyKiller87

Did you use a GM distributor cap? The Vortec 4.3, 5.0 5.7 and 7.4 are very picky about the distributors. A lot of the aftermarket ones that you get at auto zone are aluminum posts vs the GM brass posts. Also check the shaft play in the distributor, if you grab the rotor and can move it side to side its junk. If you need a new one look on ebay, there are companies selling the aluminum bodied distributors with the brass point caps for about $70 which is far less than the stocker and a ton better.

That's me ;)