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96 4.0l OHV CEL codes


will2045

Well-Known Member
Joined
Apr 16, 2009
Messages
174
City
Mt Pleasant, Mi
Vehicle Year
1984
Transmission
Automatic
Okay I have a 1996 4.0l ohv that keeps throwing a code

UPDATED: P0306 only now


cyl 6 erratic misfire
new plugs and wires
switched plug wires as well as visually verified spark
listened to injector with stethoscope and verified visually on a wet plug
compression test at 112psi
starts a little hard but always has
no using coolant or oil. both are clean when examined.
misfire seems to happen more when warmed up and ONLY at an idle... any ideas?

need help ASAP and I'm completely out of ideas.
 
Last edited:
Unhook coil
Crank engine
Remove #6 spark plug

It should be wet with fuel, never assume, lol.


That hanging device by the power steering pump sounds like the DPFE sensor, two vacuum lines and a connector, black or grey housing.

I would plug it back in to vacuum lines, if engine starts to idle rough then DPFE could be bad, which is why it was unplugged, it was opening EGR valve when it shouldn't.
If you have a vacuum gauge and pump you can test DPFE with volt meter.
Google: test ford DPFE
 
Unhook coil
Crank engine
Remove #6 spark plug

It should be wet with fuel, never assume, lol.


That hanging device by the power steering pump sounds like the DPFE sensor, two vacuum lines and a connector, black or grey housing.

I would plug it back in to vacuum lines, if engine starts to idle rough then DPFE could be bad, which is why it was unplugged, it was opening EGR valve when it shouldn't.
If you have a vacuum gauge and pump you can test DPFE with volt meter.
Google: test ford DPFE


isnt the DPFE bolted to the side of the intake? this is a canister purge solenoid type thing. i swapped what I'm 99% certain is the DPFE sensor on the intake and noticed the hoses on it were backwards (not sure if it matters) they both come off the EGR pipe going into the drivers side manifold.

I also got a stethoscope on the injector and hear it clicking plain as day but i'm going to compression test it. the miss seems to go away when it gets warmed up. im wondering if maybe its a little head gasket leak making it wash out spark at a cold idle because the miss is very inconsistent.
 
okay So I'm still having the cyl 6 misfire... I have checked the injector, plugs wires coil, and compression test all test perfectly fine. any ideas here?
 
That's all there is.
Spark, fuel, compression.

Is it actually missing now?

Have you reset the computer?
Unhook negative battery cable for 5 minutes, or use OBD Reader.

On the waste spark system cylinders 2 and 6 fire at the same time, on the power and exhaust stroke, so you can swap those 2 on the coil, just to make sure coil is working for both cylinders.

Was compression tester end wet with fuel, after testing?
Unhook coil and crank engine
Injector is working only if spark plug tip is wet, only way to tell if fuel is getting to cylinder, "clicking", noid light, or ohm test, are fine, but unless spark plug is wet it ain't been tested for fuel, lol.

Swap spark plug with #5
Just had a 1 year old plug quit on me, looked fine, would of swore on a stack of Ranger manuals that the spark plug was not the problem.........embarrassing.

A vacuum leak in the manifold could effect one cylinder, but only after warm up, cold mix would be too rich.
Weak spark will miss on cold engine but be fine after warm up and lean mix is set.
 
Last edited:
That's all there is.
Spark, fuel, compression.

Is it actually missing now?

Have you reset the computer?
Unhook negative battery cable for 5 minutes, or use OBD Reader.

On the waste spark system cylinders 2 and 6 fire at the same time, on the power and exhaust stroke, so you can swap those 2 on the coil, just to make sure coil is working for both cylinders.

Was compression tester end wet with fuel, after testing?
Unhook coil and crank engine
Injector is working only if spark plug tip is wet, only way to tell if fuel is getting to cylinder, "clicking", noid light, or ohm test, are fine, but unless spark plug is wet it ain't been tested for fuel, lol.

Swap spark plug with #5
Just had a 1 year old plug quit on me, looked fine, would of swore on a stack of Ranger manuals that the spark plug was not the problem.........embarrassing.

A vacuum leak in the manifold could effect one cylinder, but only after warm up, cold mix would be too rich.
Weak spark will miss on cold engine but be fine after warm up and lean mix is set.


yeah its still missing. I can hear it and its throwing the p0306 code still

I will swap 2 and 6 and see what happens

I will also un plug the coil pack and make sure its actually spraying fuel
 
Okay consider this my official SOS call. I have been borrowing a vehicle I need to return this friday and stilll don't have this fixed..

I pulled the compression test, Cold it wasnt great but wasn't low enough to cause any sort of misfire 112psi

I un hooked the coil and turned it over and the plug was wet with fuel.

recap so you dont have to re-read the entire thread.
cyl 6 erratic misfire
new plugs and wires
switched plug wires as well as visually verified spark
listened to injector with stethoscope and verified visually on a wet plug
compression test at 112psi
starts a little hard but always has
no using coolant or oil. both are clean when examined.
misfire seems to happen more when warmed up and ONLY at an idle... any ideas?
 
112psi is quite low, my '94 4.0l tests at 160-170psi cold, with all plugs removed for test.

Did you test a second cylinder?

Rotate crank until compression stroke on #6 then put #6 piston at TDC, mark this in crank pulley, aligned mark with 0deg TDC on timing plate.
Use timing light on #6 wire and see if #6 is firing when it should
 
Last edited:

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