How to tune 1990 chevy s10

Donald, You did not state the model, so I posted the link for the models I found for chevy van fuse box. Check the attached links,instruction and guides, Good luck
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Interior Fuse Box Location 1990 1996 Chevrolet G20 1994 Chevrolet G20...
Blown Fuse Check 1990 1996 Chevrolet G20 1994 Chevrolet G20 Chevy Van 4 3L...
fuse box diagram 1990 chevy astro van pdf 1 Docs Engine com
1990 Chevy van fusebox location Google Search

check pcm fuse sound like could be pcm problems have vechicle code scan look for code 51 which is faulty prom mem cal or ECM PCM

change air & fuel filters, EGR valve, & PCV valves need replaced ! a tune-up may help your engine also, spark plugs, plug wires, etc., etc., check all vacumn lines, tighten all throttle body bolts, on so on, good luck

They are engine grounds for all electrical components on the engine, the engine sits in rubber so it needs this type of ground.

Chevy Corvette 1990-1996 Factory Service Workshop Repair Manual

Chevy Corvette 1990 1996 Factory Service Workshop repair manual...

Covers:Chevy Corvette 1990-1996

This manual contains all the necessary instructions needed for any repair your vehicle may require from bumper to bumper.
Whether its routine maintenance, such as tune-ups and brake service, or more extensive repairs involving engine and transmission disassembly. This file provides the most reliable information to perform the job.

Accurate, clear and concise text, combined with illustrations, make it possible for anyone with even a bit of basic mechanical knowledge to safely and easily service and repair their vehicle.

Comprehensive diagrams, in depth illustrations, and all the manufacturers specifications and technical information you will need is included.

Section included:

Tune-up and routine maintenance
General Engine overhaul
Automatic Transmission
Transfert Case
Driveline
Brakes
Suspension and Steering
Body
Chassis Electrical

Format: PDF - Download
Years:1990 1991 1992 1993 1994 1995 1996
Compatibility:any windows (95-98-ME-XP-7-MAC-LINUX-IPAD-IPHONE-IPOD)

1990 Chevy 4.3 l engine runs rough at idle half the time-- sometimes it's OK, other days it's rough and can smell raw gas, as tho it's running rich... any ideas?

It happens all the time:), located on the driver side of the engine, between 3 and 5 cylinder is the temp gauge sensor usually a single green wire, locate this and repair/reconnect and your in business.

Sounds like it could be the differential, or the transfer case. 4X4?

if this happens only in the morning after you start for the first time its the clutch on the fanblade needs replacing

Have you checked the coil