1990 chevy 2500 computer issues

[tbitrouble]

I purchased a non running 1990. Rebuilt the motor and cant get it to run right. I've found evidence that the computer has been changed or tampered with. It's a 1228747. I've been reading that this model doesn't support knock sensor and ESC. Both of which I have on this motor. I need help figuring out what computer was original to this truck.

I've replaced the distributor, map, TPS, knock, TBI, plus/wires, O2(twice). It seems to run Ok with spout disconnected while cold. When it warms up it Idles high then low then high. With spout connected it misses on idle runs ok at high rpms. seems like when the computer takes over, it craps out!

[jim_in_dorris]

1228747 is original to truck, what BCC is it running. What the ??? is a spout? Hunting idle is usually (but not always) a vacuum leak.

[tbitrouble]

It's the single wire timing connector. Sorry, I've heard it refered to as a spout. I don't know what BCC is. So does the 1228747 support knock and ESC? Dealer also lists this as stock to the VIN.

Also, I've just found carbon crammed in my EGR not sure where it came from. (Crossing fingers, hope this is it.)

[EagleMark]

Spout is usually a Ford term... yes that truck cam with a 122778747 ECM in 3/4 ton models with TH400!

The BCC is Broad Cast Code and GM name for the four letter chip code that came on your chip. WHen you buy a replacement ECM it does not come with a Chip. You use your old one. It would be good at this point to open your ECM and read the BCC from top of chip to see what this thing really is and make sure the BCC matches 1228747 and not 1227747 ECM.

Carbon filled passages on EGR is common and needs to be cleaned and blown out. Can cause your vacuum leak if EGR is not closing properly.

When ECM takes over it is usually going Closed Loop, before that Open Loop. Only real change is fueling correction.

Watch your CEL when Key on? Should come on, blink and stay on till engine starts then goes off!

[tbitrouble]

Mine has the sm465. BCC is AKWH

[tbitrouble]

So I cleared the EGR valve and still have issues. I've searched long and hard for a vacuum leak and have not found one. How common is it for the intake to leak or crack on the underside?

[steveo]

if it runs that much better with the wire unplugged, it does sound like a timing issue, i'd take a gamble that you didn't time the distributor correctly? did you trust the pulley's timing mark for TDC, or...

if you suspect a timing leak and can't find it, might have to borrow a smoke machine, that's the best way to find 'em.

[tbitrouble]

Well, there is only one mark on the balancer. So I have no choice but to trust that its correct. As for procedure, I unplugged the timing wire and set to 0º TDC. Am I missing something?

[EagleMark]

Well, there is only one mark on the balancer. So I have no choice but to trust that its correct. As for procedure, I unplugged the timing wire and set to 0º TDC. Am I missing something?

Sounds good!

if you suspect a timing leak and can't find it, might have to borrow a smoke machine, that's the best way to find 'em.

Yeah them timing leaks are a bugger to find without a smoke machine...

I'm on enough pain meds it made sense too!

[steveo]

timing leak...damn i've been online too long today