10-15-06, 04:07 PM
i have a 1994 concours northstar. i have had this problem afew days now. it will run fine then start to hesitate, if u stop it idles very rough also. but it is not all the time. only code that is current is po56, would this do it? thanks for any help.
How old are the plugs & wires?
10-15-06, 04:34 PM
plugs dont know looks like the wires were changed .i have this car 3 months only
I believe PO56 is defective Input Speed Sensor in the transmission.
A few months back I developed a stumble and at the same time got a code
PO56, I found that my iss was open and had to drop my transmission and
go into it to replace the sensor($20 part $2000 job) . That did not cure
my stumble, my son and I checked everything, all sensors connected to the
PCM and found nothing. Finally after exhausting all efforts we took the coil
pak/icm off to clean them and check the connections.
My son used a multimeter to check the coil paks and found one to be bad
even though we had spark to both plugs that pak controlled.
We concluded that the coil pak went out and induced a voltage spike into
the cable harness near the plug wires and zapped the input speed sensor.
I have since made a metal shield that is placed between the harness and
the plug wires, It also protects the hvac blower motor.
Before you start tearing into it do this. Go into PCM Diagnostics and check PD72 tranaxle turbine speed, you should have something around idle speed
rpm 600- 750 , if you have 0 you have a bad iss, an open connection
between the the iss and pcm, or a bad connection in plug C-129.
If you get 0 on PD72, check across terminals B3 and B4 of the Red plug
on the pcm (these go to the iss sensor) you should read 1300 to 1450 ohms
if not check c-129 to make sure you dont have a bad connection there.
Hope this might help, post back what you find.