No spark for 98 tahoe 5.7 4x4 i have changed the ignition coil the wiring is good fuses are good but cant figure it out we have an eci system

To Remove......
1. Remove the spark plug wire from the ignition coil.
2. Disconnect the ignition coil electrical connector.
3. Remove ignition coil bolts.
4. Remove ignition coil.

To Install.....
1. Install ignition coil.
2. Install ignition coil bolts.
3. Tighten ignition coil bolts to 8 Nm the same as 71 inch pounds.
4. Connect ignition coil electrical connector.
5. And finally, install spark plug wire to ignition coil.

Did you forget a ground wire attachment? Recheck your engine grounds.
Each coil should get power on the black/white from the ignition switch, constant battery voltage. Does it? If not, check fuse 24, a 10 amp fuse in the Junction Block. Power travels from the ignition switch (in ON, RUN, or START) to this fuse, and then is spliced to each coil. Other than that, the PCM controls the current switching for the coils (for spark). The other wire from the coil (black?) goes to the pcm for earthing the primary current to the coils.

If the coils have power but no spark, it could be the crankshaft position sensor. I believe the crank sensor would be more important than the camshaft sensor for the pcm to figure spark timing.

Greg Bernett 2821 Solutions February 14, 2010
You didn't post your engine size so please pick the applicable diagram:



1996-98 4.3L Engines Firing Order: 1-6-5-4-3-2Distributor Rotation: Clockwise



1996-98 5.0L, 5.7L and 7.4L Engines Firing Order: 1-8-4-3-6-5-7-2Distributor Rotation: Clockwise




4.3L Engines Firing order: 1-6-5-4-3-2 Distributor rotation: Clockwise



4.8L, 5.3L and 6.0L Engines Firing order: 1-8-7-2-6-5-4-3 Distributorless ignition system (one coil on each cylinder)



5.0L, 5.7L and 7.4L Engines Firing order: 1-8-4-3-6-5-7-2 Distributor rotation: Clockwise

Source: spark plug wiring diagram for 98 tahoe

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  ledsled378 2926 Solutions July 24, 2010
  

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Source: Need diagram for spark plug wiring for 1997 Chevy

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  Dennis Weid. 44272 Solutions September 16, 2008
  

This was all I could come with, hope it helps.

change out your distributor cap and rotor button

WHEN TROUBLE SHOOT CAR CHECK FOR SPARK AT PLUGS FIRST IF NO.CHECK IGNITION FUSE TO IGNITION COIL OR COILS AND IGNITION MODULE.IF FUSE GOOD CAR NEED SCANNING FOR CRANKSHAFT SENSOR FAULT OR IGNITION MODULE FAULT.IF IGNITION SYSTEM OKAY CHANGE FUEL FILTER IF NOT BEEN CHANGED LONG TIME..CHECK TO SEE IF YOU HEAR FUEL PUMP RUN IN FUEL TANK WHEN YOU TURN IGNITION KEY ON FOR 3 SECONDS.THE FUEL PUMP WILL TURN ON 3 SECONDS THEN TURN OFF.IF YOU HEAR NO FUEL PUMP.CHECK FUSE AND RELAY.IF BOTH GOOD.STILL HAVE CAR CODE SCANNED FIRST.

First check power to the coil. Pull the connector off and probe the connector terminal from the pink wire with a 12 volt test light. Connect the test light clip to a ground point/bolt on the engine. The test light should come on when the ignition switch is on. If not, suspect the ECM-1 fuse is bad or the ignition switch is bad.
If there is power to the coil, next test the coil. Run a jumper from the battery positive terminal to the pink terminal on the coil itself. Pull the coil wire off the distributor and place the wire close (within 1/4 inch) to a ground point on the engine. Then, briefly touch a jumper from the black/white coil terminal to engine ground. The coil should release a spark. If not, replace the coil.
If the coil is good, suspect the crankshaft position sensor is bad or loose. I'm assuming your engine light is off, but the sensor can fail without setting the engine light. If the engine light is on, see if you can get a scan to see if a crankshaft sensor trouble code is set.
Please let me know if you have any questions.

https://s26.postimg.org/j6u1vxn61/ignition.jpg

Click on the link.
I don't know what testing you've done? How long since a tune-up? Any applicable trouble codes? To check codes yourself, at the least, you need an obd2 code reader.
In the diagram, see the pink wire at ignition coil, that is primary voltage to coil, with key on, use a test lite and see if there is voltage? If no voltage, that circuit is fuse protected, I believe ecm 1 fuse, under hood fuse block. You need to do some testing and tell us what you find?

The ignition coil may be what is killing the plug. Since yo have replaced plug and wire and it seemed to do good, the only other option is the coil for that cylinder is defective and causing the plug to foul. This engine if not mistaken has the COP coil over plug on each cylinder.

first, check all the fuses
did you check to see if there's spark at spark plugs?
did you check the fuel pressure? you need to do that to isolate fuel and ignition system.
if there is no fuel then check for fuel pump operation
if there is no spark then check the ignition system (coil, module and wirings)
if you don't have either one then the problem is in the computer system such as crank sensor, and computer itself

You didn't post your engine size so please pick the applicable diagram:



1996-98 4.3L Engines Firing Order: 1-6-5-4-3-2Distributor Rotation: Clockwise



1996-98 5.0L, 5.7L and 7.4L Engines Firing Order: 1-8-4-3-6-5-7-2Distributor Rotation: Clockwise




4.3L Engines Firing order: 1-6-5-4-3-2 Distributor rotation: Clockwise



4.8L, 5.3L and 6.0L Engines Firing order: 1-8-7-2-6-5-4-3 Distributorless ignition system (one coil on each cylinder)



5.0L, 5.7L and 7.4L Engines Firing order: 1-8-4-3-6-5-7-2 Distributor rotation: Clockwise