I have a 1995 dodge ram 1500 2wd with the 5.9 z vin code engine in. I have a problem with the way it runs. The engine has 156000 miles on it and was rebuilt at 143000. So far I have replaced the PCM, Fuel sync sensor, crank sensor, plugs and wires, IAC, TPS, MAP and replaced all vacuum lines with rubber line and eliminated all the plastic stuff. The engine idles fine, the fuel sync is at 0 done wirk a drbIII programmer. It idle fine then after you run it it the engine misses, I tried old school and held a dollar bill by the the exhaust and it did suck it in, I have checked compression all cylinders are beteween 147-152 pounds and hold, I also checked the springs on the heads they all are at 160 lbs, I ran the truck with the valve covers off to see if valves were sticking none of them do. This truck has a jacobs ignition system on it and it has burned off the carbon tip in the distributor cap. With everything I have done Am I correct in believung that if a cylider does not fire that would cause the sucktion on the exhaust. Other note the fuel pumpo is new I have 43PSI on the rail and I can also get 16oz of fuel in 15 seconds so I have good pressure and fuel volume, The injectors were cleaned out. Im ready to go crazy any help would be great. THe intake manifold has no leaks.

 

not something as simple as having two wires mixed up? ive done that idled fine then as soon as i took off it was obvious, or take a look at these pics how bad is the miss? https://dodgeforum.com/forum/2nd-gen...f-place-5.html

 

Have you checked the cat? And did you replace the pre cat o2? Also, have you checked inside the intake manifold for oil?

 

Well, a vacuum leak can cause a misfire. Not normally an issue with the Magnums as it is with the Ford Triton and new Chevy Vortec that use plastic, low yeild manifold gaskets. But regardless, spray carb or brake cleaner around the base of the intake to seek out a leak. If there is one, you'll know it.

A leaking plenum pan causes the same issue plus motor oil fouling the plug(s), but you won't be able to find that with the old carb cleaner test. Do as Z-man said and look for oil on that pan by peeking down through the throttle body.

 

I have checked the intake manifold- no leaks and I can see oil down thru the intake body.

As far as the heads I have 150psi of compression on all eight cylinders.
I have also checked the springs in the heads they all have 160lbs on the springs, also have run the engine and none of the valve springs are sticking.

All vaccum lines are new and were replaced with rubber vac line.

When I set the fuel sync a zero the engine ran good on a test drive for about 7 miles then on the return trip back It started missing. I pulled off the dist cap and found the carbon tip was melted/arc'd away.

I put new plugs and high preformance wires on it. double checked my firing order as well.

 

what about the Jacobs ign which one is it? did you just add it or has it always been on thier with no probs ? ign melting your rotor tip whats it doing to your plugs?

 

Is that a typo then? Usually, if there is oil there, and you can see it.... you have a bad plenum gasket. Wouldn't cause the issue with the dist cap though......

 

can u just unhook the jacob ingtion and run it with the stock igtion and see how it runs??

 

did you replace the cap since you say it was burnt out thats a definate misfire also you say you can see oil in the intake that means plenum gasket is bad .ive never heard of sucking a dollar bill up with the exhuast,whats that supposed to tell you?+1 on dbl checking firing order very easy to cross a wire .hope you find it let us know

 

If you can see oil by just looking through the TB, don't bother trying to diagnose any thing else until the plenum is fixed. And until it is, you are ruining the cat and o2 sensor.