Bad / Hunting idle 88 Duke when warm / hot (Page 5/8)
Patrick APR 17, 12:55 PM

quote
Originally posted by olejoedad:

It is a clip that's bolted to the frame rail with a heavy black wire.



Found this image in an old thread...
Donster APR 17, 03:46 PM
Awesome........thnx!

Now, that my scanner software has arrived, I just need to figure out how to use it.
Donster APR 19, 04:42 AM
No ground connection there.
Anyone know where it was supposed to come from? I'm assuming from the C500, inside the harness going to the passenger side rear lights?

\D
olejoedad APR 19, 08:23 AM
To the passenger side of the ECU on the fuel tank tunnel. Heavy black wire screwed just behind the center console framework rear attachment bolt.

Just re-read and saw you have an 88. Sorry for the confusion.
theogre APR 19, 06:23 PM
Ground, G400, shown is only for rear lights, maybe Cruise servo when so optioned but only for 84-87

88 rear light goes thru C500 to ground inside of cabin.

And That is 2 points.... G201 & G202
G202 is "easy," near and below ECM.
G201 is harder behind radio for most. Can barely see if look behind radio when you are under the left side of dash. Not sure on 88.

Both are unlikely damaged but frame paint and dirt can make them "weak."
G201 might clean w/o pulling the radio but will need good magnet driver so don't loose the screw. Many drivers have weak magnets that may not hold here.

A lot of things are grounded there... Including Fuel Pump.
Donster APR 25, 12:04 PM
OK, finally got my diagnostic kit & cable.
Thought I had figured out TunerPro RT with the $48 definition file, but I don't trust myself and obviously, some of the readings don't make sense. I measured voltage with a DVM directly at the terminals and had 13.6 V!
Perhaps some of you can tell me what I am doing wrong.
Here is a screen-shot of the ALDL dash and the ALDL flags.





I also have the CSV file.

BTW-Idle is still hunting, matter of fact, getting worse..........thought I was on the right rack.
HELP!
theogre APR 26, 01:16 AM
ECM is telling you it reads 9.6v and likely why you have hunting idle.

You read V w/ DVM on what terminals? at battery? doesn't mean much there.
Power, grounds to ECM still have problems as I posted above or ECM itself is "bad."

ECM has 2 power feeds. One directly from the battery, other from ECM fuse. Either/both can have problems.
To start, Check every wire to the "box" under C500.

I would carefully unplug/plug both connectors on The ECM a few times too.
Even tap w/ fingers on ECM and see if numbers change if true then likely ECM is dying.

MAT and Engine Coolant that low unless local weather in cold there but I don't think is -22°C right now.
MAT can get colder then weather because is downstream of TBI w/ petrol getting on it but engine mush be cold. Engine hot MAT easily sees 150°F at idle even in cold weather.
MAT also gets wide swings of temp as you drive too.
Donster APR 26, 02:20 AM
Thanks Ogre.

Can somebody provide me with a wiring diagram, as I don't have a shop manual for the 88-

Thanks.
Gall757 APR 26, 10:11 AM
nevermind.....thought I had a diagram....but no.

[This message has been edited by Gall757 (edited 04-26-2019).]

Donster APR 29, 01:29 AM
Anyone?

Or does someone have an 88 SM for sale? 87 SM here in Germany was sold before I had a chance to buy it.

On the ECM connectors I found the following:
Had a steady 12 V on W(hite)10 & 15 (battery and ECM fuse), although scan tool told me only 9.6 V???
Had a good ground on W(hite) 12 & 13 (system ground).
Had no ground on B(lack)12 (sensor ground for TPS & CTS) and on W(hite)14 (sensor ground for MAP & MAT), so I added ground by splicing in two wires to the harness and to the chassis, just for troubleshooting purposes. Peculiar though, I had ground, when measured directly at those aforementioned 4 sensors, so I assumed, I had broken wires somewhere in the harness???
Made no difference in the hunting idle, but feels like the car is running worse now.
Is ground on those two connections only provided when ECM is running (ignition "ON")?

Guess I need not mention that this is driving me insane now!

Thanks for ANY suggestions, especially if I did something wrong!

\D