New here, transplant from chevyhhr.net. I now have a 1994 K1500 Blazer Sport 5.7 V8 . Most of the time it runs decent but lately at about 2000 RPM it acts like its running out of gas but runs real rich. I rebuilt the throttle body. New IAC, new TPS new jets the whole works. I know its getting plenty of fuel. I also replaced a lot of vacuum lines, checked the distributor cap, rotor, plugs and wires. Not real sure where to go next. Oxygen sensor maybe? Look forward to spending a ot of time here. Thanks in advance for any help.

 

Have you checked the throttle body base gasket for a vacuum leak? Tested fuel pressure?

Have you checked the cat for restrictions?

 

I totally rebuilt the throttle body and all the gaskets including the base. No leaks there. The best I can tell the cat is free flowing, what is the best way to check that? I don't have a fuel pressure gauge but the injectors seem to have a good fan spray at all RPM's.
Any chance the EGR valve could be causing this?

 

Typically, I will pull an O2 sensor ahead of the cat and run it that way. It's loud, but effective at releasing pressure if the cat is restricted. I have also drilled holes, but that gets tedious when you have to weld them up afterwords. If there is a connection that you can take apart without damaging anything too much, that may work as well.

As far as the EGR valve goes, it is possible, but that usually causes idle problems.

 

I'll try that O2 sensor first and go ahead and replace it while its out. I could drill holes but here in Texas they will fail your inspection if your cat has been tampered with. Hey thanks for the good info, I'll post weather it works or not.