Hey all, I just recently inherited a one-owner Z28 in immaculate condition. It hasn't been driven very much at all since 2015, just short around town trips or just started up in the garage occasionally. I'm starting to drive it now and I'm having an issue. It starts right up, no problem. Idle seems a bit rough to me and is around 600-700ish (hard to tell on the gauge). Drives great, seems to have good power for what it is but after about 15 minutes the "Check Engine" light comes on but there's no discernable difference in how it runs. Today however, after the light came on I pulled into the garage and mashed the throttle a few times just to see how it was doing and after a couple good mashes it stumbled & died. It started right back up and the light was off, but a couple more good mashes and it did it again. I'm thinking something simple like the fuel filter? What are some other things that could cause this?

Fuel pump does kick on, although it does seem to get significantly louder the longer the car runs, not sure if that's common but it's really loud. Kind of reminds of what a differential sounds like when it's going bad.

 

If you retrieve the error codes, the ECM will define what it apparently doesn't like at one of its inputs. That would save a lot of guesswork and speculation.

 

Only code that shows in the ECM is 24 - Speed sensor (Speedo broke - cable?), shouldn't be causing the stalling.

 

If that is the only code, it can be disregarded as to how it affects the stalling, although it should be addressed eventually as it may affect the TCC lockup and some other functions.

Measuring the fuel pressure would be helpful. While the pump may be making more noise than you would like, it may be operating normally. A pressure reading will determine whether that's a problem, and potentially where to look next

The original fuel injectors should have been RP/Bosch units, and were pretty reliable, although that was almost 40 years ago. It may help to add some clean fuel with about 1-1½% 2-cycle oil to help lubricate the injectors, and possibly also the fuel pump. I've been doing that since around March of 2000, after removing and cleaning (unsticking) the injectors on my '86 for the third time. It has not been a problem since then. It's also on the original fuel pump.

Also, (in my opinion) you can disregard any notion that ethanol fuels are causing the problem(s). I've been running that since 1976, and still do in everything I have.