1991 Ford F-150 Ignition Timing

  • 1991 FORD F-150
  • V8
  • 2WD
  • 163,000 MILES
My 1991 Ford Lariat; V8, EFI, 5.0L seems to have an acceleration problem. Even in neutral, if I rev the motor, at about 1200-1800 RPM the motor seems to "bog down". When the RPM reaches 1800+ the truck seems to run fine. I suspect the TFI-IV module in that I failed the California Smog Test in the ignition timing section. My Chilton book says there is no adjustment for BT and AT yet he says I need to have an timing adjustment so that my PPM of Hydro Carbons are within limits. Thank you in advance.
Do you
have the same problem?
Thursday, December 27th, 2007 AT 8:11 AM

1 Reply

The only thing you can set is base ignition timing. The ECM takes care of timing on a moment by moment basis after the engine is running.

In order to set base timing you need to disconnect the spout connector, start the truck and set timing to about 10 deg BTC. Some people set it as high as 13 deg, but then you run the risk of detonation at that setting, plus emissions tends to go up the more you advance the timing.
Shut the truck off, reconnect the spout connector and that should do it for ignition timing.

The spount connector is a little plastic doohicky on the wire bundle coming off the TFI module. I just pull it out and set it somewhere safe while setting the timing.
Was this
Friday, December 28th, 2007 AT 9:06 PM

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