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4kq turbo conversions - MC code motor wiring (& questions)
Afternoon Guys and Gals!
With all the topics flying around recently, I thought I'd see if I could
start a feel
good thread. (That is, I'll feel better when my turbo conversion is
The only spider bites here were a result of the critters who reside in my
and have expressed their approval of my car with exotic web designs ;-)
Hopefully the formatting doesn't get totally trashed getting to everybody.
avoided the use of tabs to help. Here goes...
The patient is an high mileage 84 4kq, who's been patiently waiting for me
back around to her turbo conversion. I spent a lazy weekend in the garage
the ole girl to see how much progress I could make. Removed the battery
most of the interior including the dash, the damaged heater box, the seats,
carpet and soggy :-( padding, and the old brain wiring. After a little
ran the new battery feed line to the trunk, ran the heated seat wiring
the power window harness from a 87 4kq, and muddled over the 4kq and 5ktq
I have the complete wiring setups from an 86 5kt (auto) and from an 86 5ktq
The 5kt harness is in better condition, and was the one I chose to
harness consists of the various engine bay connections, the brain and its
the idle stabilizer brain, and kostal connector T14b from the wiring
After tracing through the Book of Robert, Chapter 97, verses 324 through 328
am left with a few questions. I'm hoping that some of those who have gone
or are just gone ;-) can give a second opinion confirming my thoughts.
Martin, Dave, Ben, Steve, others??
The easiest part of the wiring is the engine bay. If there's a connector,
find it a good
home. The only exception is one of the two green wires going to Terminal 1
coil pack. One of these is no longer used...
The next part is the brain. Not much to it's wiring, only it's programming.
The one question I have there is with Pin 34 (97.324 Trace 47). Bentley
lists it as a
Brown/Green wire connecting to ground. On my harness (5kt auto), pin 34 is
Gray and cut (from the factory probably). Thoughts on this are that it was
cut in the
automatics to limit boost some, and that I can reconnect this to Ground. I
to look at my 5ktq harness to confirm. Thoughts?
Moving on to kostal connector T14b we have more fun...
Pin Color Trace What/Where/Why
1 Green 79 Coil Pack to Auto Check, Main Control
3 Green/Violet 45 Feeds power to misc. items
4 Blue/White 54 Cold Start ground
5 Yellow/Blue 55 Signal to Boost Gauge in Computer Board
6 Brown/Blue 50? Ground connection
7 Green/Yellow 82 To AC stuff
8 Violet/Black 50 Signal to tachometer in Computer Board
9 Red/White 84 To AC stuff
10 Green/Brown 86 Decel cut-off Ground (?) to Computer Board
11 Yellow 47 Fuse box connection (ILa) to Fuel Pump
12 Red/Yellow 51 Power from brake light switch
13 Blue/Black 56 Ground to Computer Board Display,
Oxygen Sensor Related?
14 Brown/Green 49 Fuse box connection (BS) to Fuel Pump Relay
Now, keeping in mind the AC has been removed from this vehicle, so:
Pin Do/Don't Need (my perceived function)
Probably Yes/Probably No
1 Probably No (Signal to Autocheck unit that vehicle is running)
3 Probably No (Supplies power to several items, in remaining 4kq
4 Do Need (Cold Start Valve Ground)
5 Probably No (Signal to electronic Boost Gauge. Use a manual
6* Do Need (* This may be an undocumented connection. I
searched the diagrams
and didn't find it illustrated. But
Kostal T14b, Pin 2, BR/BL has
continuity with Brain, Pin 6, BR/BL,
Trace 50 * )
7 Don't Need (To AC stuff, and ta da... no AC. Bear this in
mind for other vehicles)
8 Probably No (Tach signal from Brain. The 4kq gets its tach
signal from the coil, pin 1
97.55 Traces 43-46. Existing 4kq wiring
will be connected to the 5ktq
coil pack instead of the other end of
Kostal T14b, Pin 1.)
9 Don't Need (To AC stuff, and ta da... no AC. Bear this in
mind for other vehicles)
10 Don't Need (To/From the Computer Board Display)
11 Do Need (From Fuse Box/Fuel Pump Relay to Knock Sensor
Light. This should be
the light used to "dump" the computer
codes. Connect to your light of choice)
12 Probably Yes (Power from brake light switch. Not sure what this
is being used for exactly,
but it is easy enough to tap this
connection in the 4kq...)
13** Don't Need (Some sort of ground feed to the Computer Board
Display. ** T2a Trace 57
connects to T2a Trace 59 ** )
14 Do Need (From Fuse Box/Fuel Pump Relay)
The last(?) piece of the Brain Harness puzzle is the Idle Stabilizer. While
it is good to keep in mind
what it is doing, it only contain 3 unused or unnecessary wires, or 1
unnecessary wire if you're keeping
AC intact. And all of those wiring can be terminated at T14b.
Idle Stabilizer Pin Kostal T14b Pin Trace Use
2/k 7 82 To AC
6/KA 9 84 To AC
15/SAS 10 86 To Computer
So to wrap this up, I'm hoping that some others can offer up reasons and
logic to change my Probably
Yes' and Probably No's to Do's or Don'ts. And for people to spot any of my
Do's or Don'ts that are wrong.
The tach signal, knock sensor light and power from the brake light switch
are my primary concerns. The
rest I'm comfortable with.
The other piece to the turbo conversion is the wiring for the after-run
stuff, turbo cooling pump and injector
fan. I think it is easier to do some custom wiring adaptations here, than
deal with the whole left side 5ktq
harness. In the future I'll probably expand on this, including more on the
aux. cooling functions, and more
on the stock 4kq left side engine bay wiring harness that must still be
Hope you enjoyed the reading...