- Location
- Houston, Tx
On his year its coil on plug, which is definitely a common cause
-
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4.2 engine swap
- Thread starter Jeepmedic46
- Start date
On his year its coil on plug, which is definitely a common cause
- Location
- Orange, Ma
Tomorrow is supposed to be warmer so going to start looking into what’s causing the misfire.
Agreen
NAXJA Forum User
- Location
- Charleston
Yep, it sure is COP ignition. Play musical chairs with the coils in that case. See if the problem follows the coil. Then you can do the same with the injectors. Out of curiosity, have you checked the spark plugs?
- Location
- Orange, Ma
No I haven’t checked the plugs. Will be pulling them tomorrow. What should I be looking for with the plugs that would cause a misfire?
Runnin'OnEmpty
NAXJA Forum User
- Location
- Southeast USA
Check the internal resistance on the plugs.
A typical value would be about 5-6K ohms,
measured from the end connector to the tip.
If you measure an open, or very high resistance,
then the plug is bad.
A typical value would be about 5-6K ohms,
measured from the end connector to the tip.
If you measure an open, or very high resistance,
then the plug is bad.
- Location
- Rainy side of Washington
Cyl 3 misfire on a coil pack Jeep is almost always fuel rail heat soak.
- Location
- Orange, Ma
Thank you, I didn’t even think about checking the fuel rail.
- Location
- Houston, Tx
That one would typically be intermittent- only on hot restarts where the fuel boils out of the rail. If its every time its more likely on the spark side.
The coil rail actually has 3 coils. It fires on two plugs at once. I think tis called waste spark. Anyways, is you pull out the coil rail, there are 4 prongs. One of them is a ground. The other 3 are to each coil. They should read the same OHMs. I forget what it should be. I remember on the two rails I measured both were low on one of the coils. My issues was not there though. I'd also check the plugs. Change with NGK plugs if needed. Check the gaps of the plugs. .035"
RCP Phx
NAXJA Forum User
- Location
- Phoenix,Az
That is incorrect, they have common B+ and 4 individual grounds that go back to the PCM!
- Location
- Orange, Ma
I changed the plugs which were gapped incorrectly and I changed the coil rail. Not showing any codes now. Checked compression and that was good. Thank you everyone for your suggestions and help.
- Location
- In a strange land
Good job.
And much simpler than a 4.2 swap.
And much simpler than a 4.2 swap.
