Later TBI ('94) on Early ('89) ECM?

[jm101]

1989 C3500 with a 454 out of a '94. That is how the truck has been since I have owned it, a little over ten years.

Recently I have been getting ready to swap the engine with another '94 7.4l. The truck has been running the 1227747 ECM that is for the '89 truck.
The TBI is for the '94 and the connectors have been swapped. I have never had any real problems with all that, so I never looked into it.

However now that I am going to be pulling it all apart and swapping the engine, is there anything to be concerned about? Would it be worth looking into a computer from a '94 and checking the pinouts etc.

Or simply continue running it the way it has been?

Thanks for the time and consideration.

 

[docstoy]

If your not having any problems with your current setup and satisfied with performance I would put it back like it is now, why ask for possible problems ?

 

[jm101]

That is my thought as well, but perhaps there is something I am not aware of.

Some previous owner did some hacking to make it work as it is, so that is where my question comes from. Is this something ya'll have seen done?

 

[tayto]

did the 89 originally come with a 7.4L? even if it did the earlier years used different injectors. 94/95 PCM is definitely a nicer unit and can be swapped over by repinning the ECM connectors. However, I am guessing your '89 has a TH400?

 

[jm101]

‘89 was originally a 454/TH400 and still has a TH400.

 

[docstoy]

You say yourself that it's been over 10 years , just be careful on the R&R and keep on trucking. Just because year of engines/ecm /connectors different as long as application is working to your satisfaction need more be said. That's just like if you were replacing a part with a reman or new component from a vendor are you concerned about what year or who made it ? Not usually your just wanting fit and function to be as good or better and if it is hurrah!!! A lot of times now there isn't a choice about year or product and even in the days these were less than 5 years old GM would often update components so that things would have to be changed or modified .