I have put a '95 LT! in a '79 triumph tr7. Since I didn't get everything from the same car, I have had to piece together the wiring. I started with a painless wiring 18 circuit harness, an OBD 1 pcm, and the lt1 harness is from a '96. I'm using tunercat and freescan. I have already downloaded a pcm4less program.

I'm trying to determine where to look for a wiring mishap that would cause freescan to report: 1) 50 rpm as soon as the pcm gets power without cranking the engine; 2) IAC value of 130; 3) desired idle value of 3187. The status window in freescan reads something like mode 1 idle header detected followed by some numbers and perpetually loops the same request for header and header detected message.

If someone can help me determine if there should be a signal that the pcm isn't getting, or if there is a signal to the pcm where there should not be, that should help. I have a helms manual that is very complete, but I just need a direction to follow. Any help would be appreciated.

Thanks

Curtis Sr.

 

I have a benchtop programming harness and when I connect to the pcm using freescan, I get all sorts of weird values like the ones you're describing, so that doesn't necessarily mean you got a problem. I'll take a look at it again tonight and get back to you with the exact values I'm getting...

 

That sounds so much like my 94 when the Opti was dying. Freescan said desired idle was 3000 something RPM and would not budge, and it ran like crap. Do you have any Opti codes? If not maybe it is related to the ignition/opti circuitry anyway, hmm.

 

The reason for my concern is that I have already put on a new opti ( I guess it doesn't hurt to now have a backup), and I have the same results after trying a new IAC control. I want to address any potential problems before I start the motor. When I attempt to capture the data from the pcm, it appears that there is none. There are no codes being recorded by freescan, and only zeros in the log that is recorded on the disk. It is the status window that cycles through the following:

From mode D1 mode 1 msg 0 data detected
requesting mode 1 msg 0 from ECU
0xF4 0x92 0x01 0x00 0x00 ...
Header sent by ECU
From on mode 1 - mode 1 msg 0 Header detected
0xF4 0x57 0x01 0x00 0x84
Header sent by ECU

I just have a feeling that I am missing something. I guess it wont hurt to see if it will run, but I thought I would get some advice from you guys first. Again, Thanks for the help.

Curt Sr

 

Curt, have you tried FORCE DATA button?

 

Dont forget to select the INTERACT radial, that always works for me.

 

Thanks Dr.Mudge. I have tried the interact mode, but I have not tried to use the force data button. I will try that this morning and report back.

Curt Sr

 

Tried the force data button, no luck! Took a chance, and was greatly rewarded.

I was able to start the car today. It sounds very nice. The readings on freescan seem normal when the engine is running, and there seems to be no problems with the idle. But the readings are still off when the motor is not running and the key is on. Oh well, I'll keep looking to see if there is some reason for it.

Thanks for your help!

Curt Sr.

 

What is the IAC value when the car is running? Normal values are around 30-50, unless you stuck a big cam in there, in which case the TB IAC can be "improved."

Heck, if it runs fine, it sounds fine to me!

 

I didn't note the IAC value. I guess I was just excited to see and hear the sound of the motor. I will be doing more testing, but unfortunately a pre-arranged busy weekend will prohibit this until late sunday or monday. I will keep you posted.

Curt Sr.

 

Yesterday, I had a chance to check the IAC values with the car running. The reading ranged from 78 to 89. I'm sure that eventually I will understand how to interpret this information, but for now I will add more data so that you can direct me.

The cam I am using is a Comp Cams XE 224/224 (.568 lift) on 110 LSA. The desired idle reported by Freescan dropped to 850 after the temperature went up, but the car maintained an idle of approximately 1050. During all of this, the chatter in the status window continues to loop the same information as before.

Anyway, thanks for helping me get through this.

Curt Sr.