4.0 head swap - running rich, missing/knock, fuel in oil, red hot cat

[Joebronco]

I finished my 4.0 head swap This week. Junkyard/Hesco style. Hesco harness. JY head (new valves) new timing, 4.0 dizzy, In line fuel pump, stock fuel line regulator, tan injectors. Pushrods at correct length.

It's idling around 700. Sounds good with a slight miss or knock. Sounds like it's coming from up top.


I drive it around the block, runs great! Slight nock gets louder with acceleration.

All of a sudden, rough idiling, dies at stop sign. I check the cat, it's glowing red. I swap the injectors, same thing. Check the valves... All good. Brand new headers, no change. I change the oil, it smells like gas and is thin...


My theory, (please correct me and any advice is welcome!) the regulator is not keeping up with the 100 psi pump, the excess fuel is not igniting and blowing by the heads into the exhaust (nicking sound) and the excess fuel is burning up in the cat...

Any advice? Insite?

 

[hole]

Do you have a fuel pressure gauge to check what you have? IIRC 44-49 psi is what you are looking for on the later years and 39-44 on the earlier.

 

[hole]

You also might run this by Lee or Bennie at Hesco

 

[Joebronco]

I'll check the fuel line pressure tonight. I'm most worried about the fuel in the oil. It's almost as if the misfire is building fuel up and it's blowing past the rings into the oil.

 

[Neuner]

Joe - I think I know what you are referring to and it had happened to me. I didn't have the hot cat, especially since I don't have one , but had bad pinging/knock after my swap.

You mentioned the Hesco CPS, correct? If so, that was my issue. They have the angle of the CPS sensor to the dampener off so that it's too far advanced. With the help of a friend who designs sensors and ECU's, we discovered this. Bennie wouldn't listen to us even though we found quite a few others with the same symptoms. We corrected it by adding longer bolts and spacers (washers) to the cps bracket mount to retard the timing.

I run the 100psi pump with a WJ fuel filter / regulator with return with no problems.

 

[Joebronco]

Nice! Do you have any photos? How much did you drop it down?

 

[Neuner]

Nice! Do you have any photos? How much did you drop it down?

No, sorry I don't think so. I'd take some pics for you over the weekend but I'm getting ready to head out of town.

Trying to remember. *Think* I got 1/2 inch longer bolts than what the kit came with and then picked up a packet of washers of the same diameter. Believe I started with 4 and then moved up to 6 on each bolt but don't hold me to it. You may have to just start with a couple and see what change it makes for your setup? I'll try and get pics but it'll be some time.

 

[Joebronco]

Ok, bumped down with 4 washers and its smoother for sure. But still rough after it hits closed loop. Still missing.


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[Joebronco]

Ok guys,

So... The cat is burning good now. But it still has a misfire.

So far since last week:

I put a fuel pressure regulator
down sized the injectors
Put on a new manifold gasket
All cylinders are between 130-140psi
8mm wires
New accel coil
New Plugs
New cap and rotor.

Still missing...


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[hole]

Have you isolated the missing cylinder, or is it stumbling across the board?

 

[Lumpy Grits]

While running in a very dark garage-Spray the wires with VERY soapy water and look for arcing.
LG

 

[Joebronco]

While running in a very dark garage-Spray the wires with VERY soapy water and look for arcing.

LG

First thing I checked when I put the new 8mm wires in.

I checked a few times, since it's the 4.0 cap, it doesn't arc as bad as the AMC 258 i6 / 4.2l .


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[Joebronco]

Have you isolated the missing cylinder, or is it stumbling across the board?

I have not been able to isolate. No codes, almost sounds like lifters but I just put in all new springs and valves...


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[Joebronco]

I have not been able to isolate. No codes, almost sounds like lifters but I just put in all new springs and valves...


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https://vimeo.com/192260216



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[Lumpy Grits]

What do you have the plug gap set at?
LG

 

[Lumpy Grits]

Ok- After hearing your video. I think you may have a lifter/valve issue.
It sounds to mechanical, to be an electrical arc.
LG

 

[Joebronco]

.040 - I ran it with .035 but when I got the bigger wires/coil I bumped it up


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[Joebronco]

That kinda where I was leaning, but the valves/springs are new. I just ordered new rockers, I'll give that a try


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[Lumpy Grits]

.040 - I ran it with .035 but when I got the bigger wires/coil I bumped it up


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Set to stock recommendation on gap.
Your dizzy cap has the brass contacts I hope.
What weight oil do you run?
LG

 

[Lumpy Grits]

That kinda where I was leaning, but the valves/springs are new. I just ordered new rockers, I'll give that a try


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Before you do anything like that. Check your cam lobes.
Take the valve cover off and watch the rockers at idle. Do they all move the same amount??
LG