problems with GM TBI

[peter paul fenske]

Hi Jeff

First off complete the swap. Got to a wrecker and grab
the aldl plug. Connect the serial data line ect to the 
aldl plug from your ecm. Then you can use a scanner or
diacom to get a handle on what is going on.

Oh yes the CE lite goes from lite ign source 12V to one
of the ecm pins. ie ecm pulls lamp low. Usually the IP has
some spare lamps which can be pulled low.

Fast IDLE and failed smog test usually indicates backup mode.
This would normally be indicated by CE lite on.
And it would take a bit to reset. Co goes offscale
since backup mode is full rich.
Backup is engaged with a major failure in the system

IAC can gum up but idle response is usually slow along with
a surging idle. Unscrew the IAC motor and give everything
a good cleaning with carb cleaner. carefull not to unscrew
pintle.

But do complete the swap with the CE lite and ALDL plug.

gl:peter

At 02:52 PM 6/15/98 -0500, you wrote:
>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.
>
>