Code 16?

[librum]

89 2.9. smooth, but backfires under load. pulled codes. Two 'goods', but with a memory code of 16. My cribsheet says code 16 is "ignition diagnostic monitor (IDM) not detected". What is that? Where is that?

 

[librum]

Update. No KOER codes other than 74 and 77. WOT and BOO. Pulled spout, engine changed, so the signal is getting from the computer. Drove with spout out. Smooth. No power, but did get up to fifty. Spout replaced, backfires under load. Trying to trace the path from wiring diagrams.

 

[RonD]

Reads like TFI module issue, how old is it?
Did you check the base timing while SPOUT was out?

Does it mostly do it after warm up?
TFI modules get heat sensitive so act up when warmed up.

Good read here in testing them: http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml

 

[librum]

TFI is less than a year old. I have found the ohm levels to look for on a bench test and will test the old one, which I have. Timing looks good. No, I can not say there is a difference between hot/cold engine, as the engine is warm by the time I get to pavement.

Thanks for replying. Will update. (And hoping I do not have to pull the intake manifold to replace the TFI again.)

 

[librum]

Bench tested the extra TFI. Good. Replaced. Ran worse. Replaced back.

Then took off the idle air control (side of intake plenum). Carboned up. Cleaned. Not best, but much better. Apparently I have found the issue. I am now going to see if I can find a replacement servo control for it. I suspect it is simply worn out or getting there. It is an odd part, so finding a good one may be an issue.