1996 4.0 OHV Bad Misfire

[Jd0gg919]

Hey guys. My truck has developed one hell of a misfire. I haven't scanned for codes yet but I have checked the plug wires for signs of arching and couldn't find anything. A vacuum leak could cause a misfire right? I do hear a loud hissing noise so thats what makes me think it could be a vacuum leak. Tomorrow I'll be checking all the vac lines and things to make sure everythings connected well. Any advise or other things I should look for while I'm in there? Thanks.

 

[jd4242]

yea i would say a cap fell off the vacuum t on the intake

 

[Jd0gg919]

Where is the vacuum T? I checked all the vac lines and they all seem good.

 

[jd4242]

yours is a 96 so might be a little dif but its on the drivers side intake manifold should be like 4 hoses coming off and one should be caped.follow the hose from the brake boster it will take you to it.i can post a pic later if you still cant find it
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[Jd0gg919]

I'll go look right now. Is it just tubes coming out of the manifold or will they be coming off of a part?

 

[jd4242]

yours is going to look a little dif because you will have egr but check all these there should be a cap or two on it.start it and fell all the nips and see if any are sucking

 

[Jd0gg919]

Alright i'll check it out.

 

[Jd0gg919]

Problem solved, for now. Plug #4 was the culprit. Swapped it out for a cheapo and it ran fine. Now to get some Motorcraft plugs and do the full change.

 

[ranger7ltr]

At least your solution was easy to fix...

I had a dead miss on one cylinder and nothing I did would fix it.. So on a whim I pulled the valve cover on that side and the intake pushrod had fallen out of the back of the rocker thanks to the heavy buildup of sludge in this engine both top and bottom end...

Loosened the rocker stand, reinstall the pushrod, and 10k miles later the misfire has stayed away...

Good find on the bad plug...Mine had bad plugs and wires...This seemed to be a vehicle that never had the hood raised to maintain...

 

[Bruce M]

I had a dead miss on one cylinder and nothing I did would fix it.. So on a whim I pulled the valve cover on that side and the intake pushrod had fallen out of the back of the rocker thanks to the heavy buildup of sludge in this engine both top and bottom end...

Loosened the rocker stand, reinstall the pushrod, and 10k miles later the misfire has stayed away...

Good find on the bad plug...Mine had bad plugs and wires...This seemed to be a vehicle that never had the hood raised to maintain...

Did it make any valve noise? My 96 has a dead miss also. It doesnt make any noise. It doesnt have a check engine light on and it doesnt smoke. I replaced the plugs and wires and on the #1 cylinder the electrode was brunt completely off. But the plugs and wires didnt fix the miss. I'm wondering if it might be the coil pack or a push rod.