i have a 1991 5.8 that runs well aside from sputtering slightly under acceleration. i'm in the process of a tune up, but have heard that a bad o2 sensor or an issue with the catalytic converter can cause this as well. thoughts?

 

Codes?

 

Can you even see the "C-O-D-E-S-?" keys on your keyboard anymore?

 

but some kind person sent me a diagram for the plug wire layout for my '92 which was missing/misfiring under heavy load/acceleration.

Turned out to be pre-ignition due to some plug wires routed too close to one another, there are a couple where adjacent plugs fire one after the other, if you don't separate those wires adequately, you get pre-ignition under some circumstances - but at idle, it's perfect.

There was a TSB for it somewhere, when I'm at home I'll see if I can find it.

 

sputtering is either Fuel or Spark...that narrows it down a bit...

 

http://autorepair.about.com/library/...bl-fo-9226.htm

http://www.alldatadiy.com/techtips/Ford/20021115b.html

Spark Plug Wire Routing for '87-93 5.0L
ISSUE: Engine miss, spark knock, buck/jerk, surge and other driveability concerns may
be caused by induction crossfire. This occurs because of improperly routed spark plug
wires.
ACTION: If spark plug replacement is performed, the correct firing order and spark plug
wire routing is essential to prevent the possibility of induction crossfire between
cylinders. Refer to the following procedures for inspection of the spark plug wire routing
and firing order. Properly reroute the spark plug wires if required.
FIRING ORDER
The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark
plug wires are routed next to each other at the separation bracket, an induction crossfire
condition can occur.
The firing order for 1994 5.0Ls & all 5.8Ls is 1-3-7-2-6-5-4-8. On these vehicles the #1
and #3, or #5 and #6 spark plug wires must be separated to eliminate the possibility of an
induction crossfire.
To eliminate the possibility of the coil wire becoming disconnected, route the coil wire
under the spark plug wires at the distributor cap.

 

thanks all for the help, also, there are no codes. cheers.

 

of course, but check that wire routing as I said - that sounds a lot like the problem I had. No issues unless there was a heavy load - accelerating uphill in OD for example. Backing off the accelerator stopped the misfiring.

 

Your tune up may very well resolve your issue, include your fuel filter as well. This is something that so many fail to change and 15 years later the truck runs rough & sputters then much money is spent on everything else trying to fix the issue.
Anyone who has bought used trucks prolly noticed the origional fuel filter still on & had to change it because they knew it needed to be changed or had issues & it got changed in the process of tuning it up, along with the air filter.

 

turns out it was the plug wires, during the tune up it resolved and then i put them along side one another just to see and problem returned. Put new plugs and wires just to make sure. runs great now, thanks all.