I am at my whits end with this thing, but I guess I will give it one more chance. I have a 94 Blazer with the vortec CPI motor. I was having starting issues with antifreeze running into the cylinders (ended up being a cracked head). SO, I replaced the heads and head gaskets. The job went smooth. Everything went back in OK. It started right up. I set the base timing to 0* and then when it's plugged in, it advances to about 20*. Now, when I try to drive it, it falls flat on it's face, like the timing is REALLY retarded. I've sunk $500 into this thing in the past 3 months and that's WAAAAAAAYYYYY too much money for what I already put in the thing. The truck did throw a code 42 after 1st start-up, but the light went out and it's not throwing it anymore (I reset the codes by disconnecting the battery and reconnecting). Any help, ideas, or anything???? Or anyone interested in buying it, let me know, lol????

 

20* at idle isn't unheard of. I'd be inclined to think that there is a problem with fuel pressure or a sensor (tps, map, or possibly O2) that is causing your off idle stumble.

How does it rev when in park or neutral?

 

There is no off idle stumble. It just has no power at all. If you get above 20 mph in 1st gear, it just sits there until I let it shift to second, then I can carry it up to about 40 in second, and so on. The truck has a new map, tps, and O2. I have literally replaced everything. Fuel Pressure is 60-62 PSI and nothing less. Cat is removed already as well.

When in park it revs up just like it should. No noises. I checked valve adjustment twice on it and its good. Like I said I'm just at a loss. I have replaced everything. I am even an ASE mechanic. I have access to scan tools and all kinds of stuff, but nothing seems to be showing up wrong.

 

So if you soft pedal it, it will accelerate, albeit slowly?

Can you cause it to stall if you move or slightly pull on the injector wiring where it exits the lower intake manifold on the front driver side corner?

 

I'll try that when I get home. But yes, I can accelerate, but it's just at a really slow pace. At lower RPM's and less than 1/3 throttle, it accels fine. As soon as there is more load, it bogs badly.

 

Man that just sounds so much like a TPS or MAP sensor problem... I know you said that you replaced them, but... I'd test the TPS with a multimeter just to be sure.

MAP sensor testing, well, the MAP should put out a voltage inversely proportional to the vacuum level it is seeing; high voltage out means low manifold vacuum (WOT or engine off) while low voltage out means high manifold vacuum (idle). Open the throttle and the manifold pressure drops. I'm wondering if it could possibly loose signal (or voltage from the PCM) when you try to accelerate.

 

Look at these two articles and see if they help out.

1st link

2nd link

 

Code 42 will generally set after setting base timing, because the Electronic Spark Control has to be disconnected under the dash to set timing. I'm not sure the problem lies there.
Any transmission/driveline problems lately? If the engine seems fine in park, maybe the driveline is the problem.

 

I realize this is an old post, but I have a recurring code 42, and the last post here has me needing to know where the disconnect is. I have some cut wires under the column... Not to mention, the distributor needs timed, PO had it out.

 

Electronic Spark Control disconnect is under the heater, right side, on the floor, just under the top edge of the carpet. You will see a single wire with a connector in the middle.