Still Can't Find MISFIRE!!!
04-19-2011, 11:02 AM
#12
Junior Member
Join Date: Apr 2011
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
wits end??
I am going way back....and I am only a backyard mechanic, but try this.....take a screw driver, and when your truck is idling, tap the MAS( mass airflow sensor ) with the handle of the screw driver ..if it bumps or runs rough this is could be it..., ( btw...same thing happened to me and it was it, different vehicle, same problem.
Hey guys,
I am at my wits end here. I have an '87 F150 302 Auto 2 wheel drive - 190,000 miles. I have been having misfire problems with the truck since I bought it 8 months ago.
Previous owner replaced both fuel pumps and filters. I replaced:
-all new fuel injectors
-new plugs and wires (correctly gapped)
-flushed and replaced coolant, changed T stat
-new distributor and module (plus rotor and cap)
-new coil
-new alternator w/belt
-Also, passed California smog back in May
All of this was done in the past 1,000 miles. Yesterday I went and bought new plug wires again thinking that one of them might be bad. I also read that there is a TSB on the correct wire routing, so I did that (since I didn't do that before) hoping that it would solve my problem. Started my truck and it runs ok at idle NOT under load. As soon as I shift into Drive or Reverse it chuggs badly - even worse when I give it gas.
So, changing my plug wires and routing them correctly according to the TSB diagram made it WORSE!
It is timed correcly, but it is definitely an ignition problem. Under a timing light, when you give it gas, it first retards then advances...that doesn't seem right to me....
I was thinking about taking these plug wires back to Napa and getting yet again another set to see if the $25 set from Napa is junk or not.
Anybody have any clue what is going on here?!?!
Paul
I am at my wits end here. I have an '87 F150 302 Auto 2 wheel drive - 190,000 miles. I have been having misfire problems with the truck since I bought it 8 months ago.
Previous owner replaced both fuel pumps and filters. I replaced:
-all new fuel injectors
-new plugs and wires (correctly gapped)
-flushed and replaced coolant, changed T stat
-new distributor and module (plus rotor and cap)
-new coil
-new alternator w/belt
-Also, passed California smog back in May
All of this was done in the past 1,000 miles. Yesterday I went and bought new plug wires again thinking that one of them might be bad. I also read that there is a TSB on the correct wire routing, so I did that (since I didn't do that before) hoping that it would solve my problem. Started my truck and it runs ok at idle NOT under load. As soon as I shift into Drive or Reverse it chuggs badly - even worse when I give it gas.
So, changing my plug wires and routing them correctly according to the TSB diagram made it WORSE!
It is timed correcly, but it is definitely an ignition problem. Under a timing light, when you give it gas, it first retards then advances...that doesn't seem right to me....
I was thinking about taking these plug wires back to Napa and getting yet again another set to see if the $25 set from Napa is junk or not.
Anybody have any clue what is going on here?!?!
Paul
03-04-2012, 01:12 PM
#13
Junior Member
Join Date: Mar 2012
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
testpilot61
Great to see each of you helping out with great ideas on cause and effect.
I ran into this same problem with my 5.4 1997 Lariet. Still have the problem with intermittent miss just off idle, I see a 3-4 hundred rpm drop momentarly. I haven't changed any wires, only plugs and that didn't help.
Jerry
I ran into this same problem with my 5.4 1997 Lariet. Still have the problem with intermittent miss just off idle, I see a 3-4 hundred rpm drop momentarly. I haven't changed any wires, only plugs and that didn't help.
Jerry
03-09-2012, 10:11 PM
#14
Go get some chicken pliers. Plastic pliers specifically for spark plug wires. With the engine running remove one wire from a spark plug - if the engine runs rougher - it is not that hole put it back on and pull the next plug wire. When you get to the hole that makes no difference when the plug wire is removed - that is the problem hole. If you go through all 8 cyl with no difference the your problem - you either havea bad spark plug or this is not ignition related. Pull all 8 plugs and inspect, I would then do a compression test. Before you start anything are there any lights in your instrument cluster lit up? Any trouble codes stored in the computer? Make sure your plug wires are in the correct position on the distributor and at the spark plug.
A vacuum gage can indicate valve guide or plugged/seriously restricted exhaust.
A vacuum gage can indicate valve guide or plugged/seriously restricted exhaust.
Last edited by Phyer Phyter; 03-09-2012 at 10:28 PM.
03-09-2012, 10:21 PM
#15
You should not have any arcing any where along a plug wire. Make sure your plug wire is snug on the metal tip of the plug and that the plug wire boots fit snugly on the plug and that there are no holes in the boots.
Last edited by Phyer Phyter; 03-09-2012 at 10:29 PM.
06-24-2014, 11:00 AM
#16
Junior Member
I know this post is old.... But in case someone new looks at this, I had the same Problem in one of my older fords and it ended up being a Valve not closing all the way. No engine codes where triggered, Also with all those upgrades and larger injectors the Computer needs to be chipped and then sent to the dyno for further fine tuning. Hope this helps!
