Misfire, Running Rich

[east302]

I’d get a subscription to alldatadiy, it’s about $30 per year. Here is the diagnostic for P0172 for a 1998. Maybe it will help. I didn’t go through it all, but do see a regulator leak as a possible cause.

I agree, your fuel pressure decline does point to either an injector, regulator or pump check valve leak. It should hold spec pressure of 60-66 psi for a while - longer than twenty seconds, that’s for sure.

To officially diagnose, you’d need to install isolation valves in place of the fuel filter to see if it’s at the pump or injector assembly. Alldata has the GM procedure for it, but I’d guess an injector/regulator leak. It’s easiest to just replace the whole thing (regulator and injector upgrade to MPFI is very common).

 

[OR VietVet]

Got the pressure gauge.
Engine running - a bit over 50 psi
Key on, Engine off - jumps up to a hair over 50 then drops over 20-30 seconds to near 0. Stops a second or 2 around 20.
Can't tell a difference when it is missing.
Notice a few things, the cement near the tailpipe is black and looks like liquid is coming out of the pipe(drops) I can't smell at all and didn't have a match handy to test if it is flammable or not.

The black/sooty watery drip is water that is carrying some of the black soot/rich mixture through the exhaust system. The water is a by-product of the exhaust process.

 

[Donf]

Thanks, I have gradually assumed that I was in for changing the furl injectors.
Some problems:
Doesn't look that hard but I've moved a few years back, most of my tools are inaccessible.
I do have several socket sets and think I have that covered. Alas, my torque wrenches are with deep in the storage building. So I guess all I need now is the torque wrench and the hooked pick, right?

Best place to get the injector assembly? Prices seem all over the place. How about the gasket?

Anything else? I guess I need to clean the throttle body and MAF sensor.

One video recommends removing the compressor, Do I need to? I guess I could, just hat do remove things unnecessarily.

 

[east302]

Yes on the torque wrench.

Delco or Delphi (same thing, last I heard) for the injectors. Mine came with the fuel line o-rings and appropriate gaskets - think there was the upper intake gasket, the throttle body gasket and the one that the injector housing goes through. Could be wrong though.

When I did mine I was pulling the lower intake as well, which does require moving the compressor and it’s bracket out of the way. I would think that you can swap the injectors by pulling only the upper intake. Take a look, see if it’ll hit anything.


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[Donf]

Anybody know the proper torque, now that I know it's plastic I have become a bit more wary.

Had a 289 in a '65 Comet Caliente back in the late '60's. Sucker was a rolling advertisement for Heli-coil .

 

[east302]

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[Donf]

Thanks!
Exactly what I needed.