Engine misfiring

Tiny
C-QOC
  • MEMBER
  • 1996 FORD F-250
Hi there,

I have a '96 Ford F250 Super Cab 4x4 with a 7.5L engine/automatic trans. Milage is 115k.

Recently the engine began to run rough. It began slowly but progressed to the point now that it won't even idle when warm. The problem exists throughout the RPM range although it appears to smooth out some right before it shifts into a higher gear.

I suspected worn out plugs and relaced the plugs, wires, and the distributor cap and rotor. The problem remained.

Additionally, the Check Engine light is NOT on. Other things looked at include a visual inspection of the vacuum lines which appeared serviceable and I also pulled the plug wires one at a time to see if there was a dead cylinder with no noticeable results. I don't think it's a fuel problem as there is some popping from the exhaust indicative of raw fuel being dumped into it and there is also a fuel-rich smell to it.

An inspection of the new rotor revealed that only about half the contact blade shows any sign of wear. I suspect that the ignition is only firing half as long as it should and this is insuffcient to reliably ignite the fuel-air charge.

I'm thinking that either this is a sign of my coil failing or the pick-up coil in the distributor is failing. However, before I go shotgun-troubleshooting, I would like to know if I'm on the right track or if there's anything I've overlooked?

I replaced the coil. When I looked at the electrode closer I noticed that it was badly pitted and corroded (see pic). I thought for sure I had found the problem. Unfortunately the issue still remains.

I'll be replacing the distributor next (rather than go through the hassle of completely disassembling the current distributor just to replace the pick-up coil. It's only $25 more for the whole assembly).

If that doesn't work, I'm out of ideas. Any suggestions?

Thanks,

Calamity
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Sunday, October 7th, 2007 AT 5:38 PM

9 Replies

Tiny
KEN
  • ADMIN
Hello Calamity,

This problem sounds like you have low compression in one or more cylinders. Lets remove all spark plugs and check here is a guide to help you get the job done.

https://www.2carpros.com/articles/how-to-test-engine-compression

This guide can help as well

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run this test and get back to us.

Cheers, Ken
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Monday, December 18th, 2017 AT 1:29 PM
Tiny
EZONMENOW
  • MEMBER
  • 1995 FORD F-250
  • 212 MILES
Have a 1995 f250 7.3 powerstroke. Left side all 4 injectors dont fire. Ohm tested harness from head to IDM. Tested good. So I put an IDM on it. Still wont fire those 4. Have tested for voltage and there is none. There is on right side. Dont know what to thin
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Monday, December 18th, 2017 AT 1:29 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Your posting got cut off. Can you put the rest of your post in your reply.

Have you changed the oil at the right time intervals? Is the level correct. You need oil pressure to fire the injectors.

Roy
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Monday, December 18th, 2017 AT 1:29 PM (Merged)
Tiny
EZONMENOW
  • MEMBER
Iv repost this so it reads rite SORRY ABOUT THAT
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Monday, December 18th, 2017 AT 1:29 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Nope. Still got cut off. Put here in your reply.

Roy
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Monday, December 18th, 2017 AT 1:29 PM (Merged)
Tiny
NCHUNTER
  • MEMBER
  • 1999 FORD F-250
  • V8
  • 4WD
  • AUTOMATIC
  • 178,000 MILES
Engine Performance problem
1999 Ford F250 V8 Four Wheel Drive Automatic 178000 miles

I have been having problems with my F-250 spitting and bucking when I give it gas, I have changed all 8 Coil packs and spark plugs. But it is still not running right. I changed the fuel filter last year when I was having simuler problems. I was thinking that maybe the injectors are bad, and was going to replace them next. Is there anything else I might look at that could be causing the problem?
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Monday, December 18th, 2017 AT 1:29 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Possible causes

Oxygen sensors
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
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Monday, December 18th, 2017 AT 1:29 PM (Merged)
Tiny
PAUL80
  • MEMBER
  • 1999 FORD F-250
  • V8
  • 2WD
  • AUTOMATIC
  • 230,000 MILES
Engine Performance problem
1999 Ford F250 V8 Two Wheel Drive Automatic 230000 miles

quick question. My truck started miss firing all of a sudden. I can floor the truck and it picks up accelertation very slowly. The truck miss fires. Try to give it gas while I am running it and it shakes a bit.
Could it a be coil or sensor. It does knock a bit when you turn it on but then goes away. When I put a gas treatment cleaner the other day it went away. But about a month later it came back worse and has been like that ever since.
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Monday, December 18th, 2017 AT 1:30 PM (Merged)
Tiny
BILLYMAC
  • EXPERT
Hi yes it could be a coil a boot or a plug. You need to isolate the cyl. May just need a major tune. Good luck billymac
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Monday, December 18th, 2017 AT 1:30 PM (Merged)

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