Advice sought!
10-27-2011, 06:00 PM
#1
Advice sought!
I recently purchased a 1990 F150 4x4, standard trans, I6/300/4.9 liter motor and I have a dilemma that I am looking for advice on:
When driving the truck at low speeds, (25/30 mph), the motor sounds like it is missing when I lightly accelerate. (When the missing occurs the truck feels "jumpy.") It runs great when first starting it, (cold or hot) and the "missing" does not occur when I give it a lot of gas, whether in neutral or when driving.
My friend who is a mechanic is helping me with this and we are both stumped after doing the following maintenance:
New spark plugs (with proper gaps set), new fuel filter, new distributor cap and rotor, new water pump, belts, and thermostat.
We checked the EGR and it seems to work fine.
The next step is to replace the spark plugs, even though they look ok, it would probably be wise to have new ones.
We doubt that the plug wires are the issue and before taking the truck into a shop, any advice as to what could be causing the "missing" issue is appreciated!
Thanks,
Nabor J
When driving the truck at low speeds, (25/30 mph), the motor sounds like it is missing when I lightly accelerate. (When the missing occurs the truck feels "jumpy.") It runs great when first starting it, (cold or hot) and the "missing" does not occur when I give it a lot of gas, whether in neutral or when driving.
My friend who is a mechanic is helping me with this and we are both stumped after doing the following maintenance:
New spark plugs (with proper gaps set), new fuel filter, new distributor cap and rotor, new water pump, belts, and thermostat.
We checked the EGR and it seems to work fine.
The next step is to replace the spark plugs, even though they look ok, it would probably be wise to have new ones.
We doubt that the plug wires are the issue and before taking the truck into a shop, any advice as to what could be causing the "missing" issue is appreciated!
Thanks,
Nabor J
10-27-2011, 06:35 PM
#2
Senior Member
Check for Codes first - if that doesn't lead you on the path to a fix I would recommend testing the TFI Module & P/U in the distributor.
http://351winsor.com/joel/Ignition_Systems/tfi2.html
(I'm assuming the I6 engine has the same basic ignition set-up as the V8's - I've only worked on these era trucks with 5.0 or 5.8)
I had a similar missing / stumble while driving on my 91 5.8 that ultimately turned out to be a faulty TFI Module.
http://351winsor.com/joel/Ignition_Systems/tfi2.html
(I'm assuming the I6 engine has the same basic ignition set-up as the V8's - I've only worked on these era trucks with 5.0 or 5.8)
I had a similar missing / stumble while driving on my 91 5.8 that ultimately turned out to be a faulty TFI Module.
