99 TJ 4.0 engine misfiring

[mikekirk9020]

At my wits end. 99 TJ 4.0. Engine misses at idle and seems to smooth out at higher RPM. Have replaced and checked, rotor, cap, wires, plugs and finally injectors. Did not drop the money on the injectors until I checked signal coming through the wires to them. Some.of them were OE and corroded so no big loss. Fuel rail pressure was right on the money.

Engine missing on #3 and #4. Throwing p0303 and 4 codes.

Next ideas are MAP and possibly Coil.

Other thoughts?? Help?

 

[Moglocker]

At my wits end. 99 TJ 4.0. Engine misses at idle and seems to smooth out at higher RPM. Have replaced and checked, rotor, cap, wires, plugs and finally injectors. Did not drop the money on the injectors until I checked signal coming through the wires to them. Some.of them were OE and corroded so no big loss. Fuel rail pressure was right on the money.

Engine missing on #3 and #4. Throwing p0303 and 4 codes.

Next ideas are MAP and possibly Coil.

Other thoughts?? Help?

First I would Do a complete compression test

 

[mikekirk9020]

First I would Do a complete compression test

First thing in the AM. Can't figure out how 2 cylinders would go at the same time?

 

[macleanflood]

Ohm check the coil before you replace it.

Compression lost on neighboring cylinders could be the head gasket between them.

-Mac

 

[Moglocker]

Ohm check the coil before you replace it.

Compression lost on neighboring cylinders could be the head gasket between them.

-Mac

Replace with tupy head?or is 99 safe?

 

[ColoJeep]

Replace with tupy head?or is 99 safe?

99 was the last good year. 0630 head.

 

[macleanflood]

99 was the last good year. 0630 head.

99 was the last good year of the TJ.

=)

-Mac

 

[ColoJeep]

99 was the last good year of the TJ.

=)

-Mac

We have a 99 and a 04 , I like the 99 better.

 

[Moglocker]

99 was the last good year. 0630 head.

I wonder why the 2000-2002 were crap?i didn’t spend a dime on mine when it started missing,i just found a rebuilt tupy and all is good.

 

[ColoJeep]

I wonder why the 2000-2002 were crap?i didn’t spend a dime on mine when it started missing,i just found a rebuilt tupy and all is good.

TUPY 0331 heads seem fine , other 0331 heads were too thin in some areas.

 

[Moglocker]

TUPY 0331 heads seem fine , other 0331 heads were too thin in some areas.

Oh got it,I didn’t realize the 99s had a different part number.

 

[mikekirk9020]

Update

First thing in the AM. Can't figure out how 2 cylinders would go at the same time?

To anybody following. Compression tested 120 in all cylinders except #3 and #4. 60 and 0 respectively. New head gasket time.

Thanks

 

[macleanflood]

If that's Grants Pass Oregon I'm an hour and change away if you need any help or tools.

-Mac

 

[mikekirk9020]

If that's Grants Pass Oregon I'm an hour and change away if you need any help or tools.

-Mac

Thanks. Yup GP Oregon. I have done heads before, but this will sit till spring. Rotator cuff surgery on Wednesday. Thanks for all your help.

 

[Chris]

I'd also be inspecting the wiring harness too.

 

[Moglocker]

I'd also be inspecting the wiring harness too.

Don’t just do the gasket,hopefully he will have the head rebuilt.(valves etc.)

 

[mikekirk9020]

Don’t just do the gasket,hopefully he will have the head rebuilt.(valves etc.)

It is headed to the machine shop.