I recently got a 91 z28 5.7. It ran fine until a few weeks ago, the PO replaced the fuel pump & gave it a full tune up because it sat for a few years before he got it.

My problem is that it sputters when the engine is cold & hot. Sometimes it will run fine, then back to sputtering again. Also my SES light comes on after driving it for 10 min with my foot on the gas. It doesn't come on while im in traffic, just on open highway driving. When I turn it off & restart the light is off. What could be the problem & would it cause it to sputter?

thanks in advance......

 

The SES light im going to have to guess is EGR related. Try pulling the codes see what it gives you.

 

Could be as simple as clogged fuel injectors, if the car has been sitting for a long period of time. You might just try running some fuel injector cleaner through yours, or getting a fuel injection system cleaning done by a mechanic.

Mine displays a similar 'sputtering' behavior -- to the point of quitting when it gets up to operating temperature. I've potentially tracked my problem to failing fuel injectors, which is apparently a common problem on the TPI engines from this era. I'm told the original injectors weren't very durable to begin with, and ethanol-based fuels apparently accelerate their decline. Check the resistance on your fuel injectors; it's fairly easy to do if you've got a multimeter and about 20 minutes. If the specs for the L98 TPI engine you have in your car are the same as for my LB9 TPI engine, the injectors should all be reasonably close to 16 ohms; and all the individual values should be within plus or minus 10% of each other, I think. If some or all of the injectors are much off of 16 ohms, you probably should replace them. Even though four of my injectors are still reading good, they're all the original factory injectors, so I plan to replace all eight in the near future; mainly to save myself the hassle of doing it again when the other four go south on me -- as they almost certainly will.