94 4.3 Vortec skipping under load

[french69ssrs]

Valve Job ?
My 94 S10 4WD w/ 150,000 mi. when loaded has a very bad skip. I filled it with Firewood and it runs like on 3 or 4 cyl. Acts the same when I tow a trailer with my John Deere 318. CPI replaced @ 125,000 mi. and a Rebuilt Dist. full tune up, Cap, Rotor, Wires, Plugs this past summer.
I haven't seen much about these needing Valve Jobs.
Thanks, Timmy from Connecticut

[OverBoardProject]

A comperssion test will tell you if you need a valve job, but theyre probably fine.

Just try backing of your timing a little, and see what happens. It'll probably go away then

[sector95]

Some things to consider:

Fuel filter.... last time it was replaced was?????

Check the spark plug wires.... make sure they are all the way into the distributor cap (sometimes the boot traps air and causes them to pop off slightly when they get warm)... check the plug connections making sure the connection is snapped completely onto the plug.

Bad gas or too much water in the tank..... EFI systems are supposed to have a "mixer" to blend any condensate (water) with the fuel..... try a few cans of F/I or carb cleaner or dry gas.

Check for proper fuel pressure at the injector rail or central point.... You have a '94..... should be a throttle body.... didn't think the "Z" engine was made back then......

Your timing is computer controlled.... you should check to make sure the base timing is correct.... don't "hotrod" it by setting to anything other than the factory initial setting.... the computer needs the correct base line....it's the old "garbage in garbage out" theory.


Just a few things I'd look at if it were my truck.....


mike

[cobra1]

missing under load is a sure sign of an ignition problem. usually bad plug wires. could be a weak coil as well.

[jimmyv-21]

dont forget fuel pressure or injecters. a skipping problem is not always ignition- takes fuel and spark to create combustion. it may need the injectors cleaned, and your fuel pressure my be low. another common problem with the blazer/s10 when it hesitates or skip is the cat converter, or the o2 sensor. also the throttle body may be dirty. i would start with making sure you got good fuel and good spark.