My 1994 Blazer seems to be losing power as soon as you begin to accelerate. It felt as though the timing was retarding badly. So last night, I threw a timing light on it. All measurements were with the EST connected. Sure enough, the timing was like 12 degrees at idle (about right), went up to like 20-24 degrees @ 2000 RPM (still pretty good) and then at 2500 RPM, it drops all the way down to about 4-6 degrees. If you rev it to any RPM above that, its stays at like 4-6 degrees. The motor is quiet, there are no knocks/unusual noises. Would this just be a knock sensor? The timing does not bounce around too badly so I doubt the chain is too worn. Just looking for any helpful advise.

I'm also still getting a nasty miss at idle when its cold. I have replaced the MAP, O2, IAT, coolant temp sensor (one that has 2 leads for PCM), and the fuel injector unit. Fuel pressure is a great and steady 58-60 PSI (right in spec for the CPI engines). I am about out of ideas. Everything is new except the module, but even it has been replaced at one point because its not a GM module.

 

Disconnect and remove the O2 sensor. Then take it for a spin to see what happens. You'll have an exhaust leak, but if the catalytic converter is clogged, it will allow the truck to run better.

 

The cat is already cut off and there is a straight pipe welded in. It's like its getting a false knock. I even run premium gas in it (always do in all of my cars).

 

I'm have the same problem but at just above idle and higher. Did ya ever find yer problem??? Pop's

 

Hey bud, check the knock sensor (As you thought of originally). Check to see if the insulation around the spot where the wire comes out has melted, this is how they typically fail. The only other thing I can think of would be a faulty pcm, leaking capacitors or something?

-Kyle