Erratic Idling and weird check light UPDATE!

[GalDemSuga]

Folks
I've finally finished the rebuilding of my work truck and now she wont run right.

The motor was pulled complete in turnkey state from my wrecked truck and ran without a hitch. The ECM is from the new/old truck I got for its body.
I redid the TBI and used new gaskets etc and made sure that I had no vaccum leaks. I started her up and she idled for a sec and then started to surge before dying.

I broke out the laptop and tried WinALDL to see what I could find. There are no codes being displayed eventhough the light is on in the dash. The WinALDL dash display shows nothing, nor do I get any sensor or flag data or error codes.

Also, after the motor dies I can still hear the injector firing. I tried to jump connectors A & B to see if I could get the codes that way and nothing happens. The light stays solid.

Could I have a bad ECM?

Well, since I couldn't communicate with the ECM, I got one from Autozone and swapped in my PROM. Now the truck runs great, allthough I now have a code 43. I will change my exhaust manifold gaskets as I'm hearing a knocking sound from the motor "only" when I accelerate.

 

[k5zombie666]

I get a knocking noise too when step on it real fast, or when i punch it getting on the freeway. What is it? Any solutions?

 

[GalDemSuga]

I get a knocking noise too when step on it real fast, or when i punch it getting on the freeway. What is it? Any solutions?

Last time I had this issue it was just a blown exhaust manifold gasket. I purchased all new ones today and will install them tomorrow. I expect that to solve the problem. I will update the post.

 

[4X4HIGH]

I get a knocking noise too when step on it real fast, or when i punch it getting on the freeway. What is it? Any solutions?

Your issue is detonation. The first thing to check is for proper ignition timing. If it's a FI engine then next check the knock sensor. Bad fuel, too low of an octane for a given compression ratio, running too lean or too rich, or vacuum leaks can cause this issue.

 

[GalDemSuga]

Your issue is detonation. The first thing to check is for proper ignition timing. If it's a FI engine then next check the knock sensor. Bad fuel, too low of an octane for a given compression ratio, running too lean or too rich, or vacuum leaks can cause this issue.

I remember getting this advice from you earlier last year. As a result I changed the knock sensor, checked for vacuum leaks and eventually changed the exhaust manifold gaskets. Turns out that was the source of my leak. I'll follow this advice again and hope it solves my issue.