problems with GM TBI

[Jeff Bratcher]

This is my first post to this newsgroup so I apologize in advance if
this is not an applicable message.

I've inherited a 1984 Jeep CJ-7 that had recently had a motor swap to a
1989 Chevrolet 4.3L TBI. After having the Jeep for about 9 months I
began noticing the following problems:

Upon cold start up it would run great until I shut it off. When I
immediately restart it (ie after going into a store, etc.) I noticed
that it would stay at high idle and would not come back down to normal
idle until the Jeep was shut off and sat long enough for the motor to
completely cool off (overnight usually).

I decided I could live with the high idle since it wasn't my main mode
of transportation - until I recently went in for the Texas Inspection
test at which time it failed the low-idle emissions portion (CO was too
high). (Note: It passed all tests last year with no problems - even
without a catalytic converter.)

I then decided to take it to a specialty 4x4 shop here in the DFW
metroplex to see if they could fix the idle problem, but they gave up
after a couple of weeks because they could not get any error codes out
of the ECM. I'm afraid that the mechanic that did the motor swap did not
get everything installed that was needed. There is no "Service Engine"
light that I can find.

Any suggestions on what I might try? I've contemplated a new wiring
harness swap for the ECM and TBI but was hoping I could try some other
options first. How important is the catalytic converter? Do I need to
install a "Service Engine" light? Might it be the O2 sensor?

I apologize if this is not the proper place to post this message, I
found this newsgroup on the Web after some "fuel injection" topic
searches. I'm an electrical engineering graduate and feel very
comfortable with replacing electronic components etc.
-- 
Regards,
Jeff Bratcher
Electrical Engineer
Motorola, Inc.