Help..NEW MOTOR in a 1993 with timming problem

I put a new GM factory 4.3 in my 1993 truck and for some reason I can't get the timming right. This is the deal.
First I would unplug the brown wire from the distributor and start the truck, then I would line the timming mark up on TDC (0 deg) and tighten the distributor back up, then I would shut the truck off and plug the brown wire back in.
Now here's the trouble. When I would rev the motor up with the timming light on, the timming mark would be at TDC until I rev the motor, but as soon as I rev the motor gradually the timming mark wouldn't move until about 1500 rpm's then it would jump from TDC to beond the point were I can even see it. For some reason the mark isn't gradually advancing. Also when the motor is hot it doesn't want to start very good, just like the timming is to far advanced or retarded to much.
Anybody have a clue on whats up with that??
I'm thinking it could be the ECM but not sure. I really don't want to guess on a $80.00 part.
Thanks for the help.

To time the engine with a lite for the base timing, leave the est ( brn wire) disconnected.

The timing mark on the balancer will go out of site or almost out of site when the timing is checked with the est wire is reconnected.

Well this is the thing, even when the brn wire is hooked back up, the timming mark is at tdc until I rev the motor. When the motor get's to about 1500 rpm's then the timming mark just jump's from tdc to who knows were.
Isn't it sapose to gradually advance? I don't know for some reason I don't think it's advancing right. The truck feel's dead from the start and lacks power. I guess I should say this also, when I first started the motor after I put it in, I forgot to hook up the ground wire from the battery ( to the block) but I did have the ground straps hooked up on the back of the block. So when I first started the truck it burnt off the little ground straps from the back of the motor to the firewall. I did fix the ground straps and hooked up the main ground wire. So if that helps anybody with some ideas.

On my 90 K1500 with the 5.7, the timing will be at 20 degrees advanced with the EST wire reconnected.

You may have an issue with the ground for the knock sensor or ESC module. If you have access to a scan tool, you should look at the knock count.

Is the check engine light on, any codes stored?

//2000CAYukon

Well I have a scan tool and I have checked everything that I could think of. But I'm not sure what the knock count should be around, I guess I never thought of that being the problem, but I can recheck it and post some #,s for you. I did replace the oxy sen. because the system wouldn't go into a closed loop after it warmed up. Everything seems to check ok now. But I really don't think it is.

The truck feels real doggie when it's cold and you have to play with the gas peddle to find the sweet spot for power. Everything from the fuel pump to the injectors was replaced so I know it's not a fuel problem. I guess thats why I'm thinking it's timming. Like I said it a hard starter after it warm also, I guess thats why I think it's a timming issue.

Thanks for the help

Well I have a scan tool and I have checked everything that I could think of. But I'm not sure what the knock count should be around, I guess I never thought of that being the problem, but I can recheck it and post some #,s for you. I did replace the oxy sen. because the system wouldn't go into a closed loop after it warmed up. Everything seems to check ok now. But I really don't think it is.

The truck feels real doggie when it's cold and you have to play with the gas peddle to find the sweet spot for power. Everything from the fuel pump to the injectors was replaced so I know it's not a fuel problem. I guess thats why I'm thinking it's timming. Like I said it a hard starter after it warm also, I guess thats why I think it's a timming issue.

Thanks for the help

Is it possible the balancer is different on the crate motor than the one that came off the old engine. If you still have it, I would compare them to make sure they are the same.

//2000CAYukon

The crate motor didn't come with a a balancer, but I was thinking that maybe the outer part of the old balancer had spun a little.

Heres some info

Block learn 136 to 140
o2 cross counts 204 and it keeps going up
map sensor 1.03 volts
engine rpm 650 to 675
throttle sensor .64 volts
knock sensor 56
prom Id 3011
idle air motor position 16 steps
Integrator 127
Block learn 136
system is in closed loop and the rich lean flag is switching

? what rpm should this motor idle at? It has a 5 speed.

Heres some info

Block learn 136 to 140


The ECM thinks it is running a little lean so it is adding fuel. 128 is neutral. Above 128, the ECM is adding fuel, below 128, the ECM is removing fuel.


o2 cross counts 204 and it keeps going up
map sensor 1.03 volts
engine rpm 650 to 675
throttle sensor .64 volts
knock sensor 56


This should be knock count. If you started your engine and let it idle until is warms up, 56 is really high. On my 90 K1500 with 125K miles, I will see the knock increase if I floor it. Every time this number increases, the timing is retarded.


prom Id 3011
idle air motor position 16 steps
Integrator 127
Block learn 136
system is in closed loop and the rich lean flag is switching

? what rpm should this motor idle at? It has a 5 speed.

My auto idles around 550 and I think the manul idles around 600 or 625.

//2000CAYukon

So what would you look for as being the problem?
Timming, fuel or bad knock sensor.
I also noticed that the truck when it's warm would have a slight miss, just like the motor stumbles at idle. I've replaced the plugs and wires also a new dis. cap and rotor. I've also checked the valves to make sure that the rocker arms weren't cranked down to far. This is how I adjusted them, Lossen the rocker up until it started clacking then tighten them back up a half turn past the clacking sound. I don't know some thing is srewy some were....