Mechanics

F150 IGNITION TIMING

1991 Ford F-150

Engine problem
1991 Ford F150 V8 Two Wheel Drive Automatic 163000 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.
Avatar
Gyesionek
December 27, 2007.




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.

Tiny
Indyuke
Dec 28, 2007.


AD