Started misfiring on a road trip - JeepForum.com
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post #1 of 25 Old 10-27-2021, 12:58 AM Thread Starter
GmanWJ
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Started misfiring on a road trip

275 miles into a 550 mile road trip, heading through San Francisco at night, got back onto the highway and she started misfiring, flashing CEL. Stopped to refuel, stalled when the RPMs dropped near idle.

Did the key dance, found P0300, P0301, P0302; misfire codes for cylinder 1 and 2.

Replaced the OPSU just before this trip and also pulled P0523, OPSU voltage high. This code since disappeared.

Managed to get home. Pulled spark plugs to inspect and check gaps. Gaps were between 0.044 and 0.050, so a bit high. Regapped to 0.040. Plug #2 was pretty nasty, #1 was better, see pics.

Just now put my code reader on it and pulled P0205, P0300, P0301, P0302, P0304.

She does not want to run. Any ideas here? Wondering if this could be CPS or KPS or something worse.

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post #2 of 25 Old 10-27-2021, 02:19 AM
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It wasn't ever plugs - and it's spreading.

No bueno.

1999 WJ Limted - Ex Soccer Mom ride turned Rule 25 Compliant Bike Hauler
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post #3 of 25 Old 10-27-2021, 05:41 AM
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Replace all the plugs clear the codes and see what happens.
leadsled jeep and Delta0 like this.
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post #4 of 25 Old 10-27-2021, 06:17 AM
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for p0205 might want to check the inj connector at #5, how did plug look?

Maybe a compression and leak down test, your #2 seams fouled with oil, I think I see same oil deposit developing on#1.

Along with the p03xx codes was there anything in freeze frame or pending?

This 4.7 is not a HO am I correct?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #5 of 25 Old 10-27-2021, 08:45 AM Thread Starter
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I gave the injectors and connectors an external inspection but saw nothing obvious. Most of the other plugs looked normal except for the gaps, but one of them had a frosted white appearance ... Was that #5? Maybe, will need to look again. Will do compression testing and revisit plugs.


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post #6 of 25 Old 10-27-2021, 11:21 PM Thread Starter
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Quote:
Originally Posted by jtec View Post
Along with the p03xx codes was there anything in freeze frame or pending?

This 4.7 is not a HO am I correct?
Not a HO, correct.

I pulled the freeze frame data with my Actron CP9145 that I bought like 15 years ago.
P0300
RPM 2624
Load 65.9%
MAP 27.9 "Hg
Coolant 199F
Veh speed 50 mph
LT FTRM1 0.0
ST FTRM1 0.0
LT FTRM2 0.0
ST FTRM2 0.0
Fuel Sys1 Open1
Fuel Sys2 Open1

I do not know what those last six items mean but it looks funny to me.

Cylinder 6 spark plug had a light tan powdery type appearance, see pic.

I can not figure how to find pending codes with this tool, maybe not possible.
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post #7 of 25 Old 10-28-2021, 02:03 AM
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Quote:
Originally Posted by V8GCZJ View Post
Replace all the plugs clear the codes and see what happens.
.
The way to go.
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post #8 of 25 Old 10-28-2021, 02:51 AM
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What plugs are you running Gman?

It looks to me like you may be running the wrong plugs.

It's normal that as engines wear, different cylinders need different heat ranges.
Matching heat range to cylinder was part of tuning last century.
Perhaps it still is?

https://www.championautoparts.com/Pa...ark-plugs.html
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post #9 of 25 Old 10-28-2021, 03:38 AM
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yes the items dont seam correct. at that temp & RPM I would expect closed loop.
Lets check scanner again when warmed up, but not checking freeze frame - does it display CLOSED LOOP?

Some basics
Are you consuming any - oii or coolant?
A quick look at oil fill cap.no milky deposit?
A compression test.
Seeing any P046x codes - check pending and history also.

*LT FTRM1 0.0
ST FTRM1 0.0
LT FTRM2 0.0
ST FTRM2 0.0
Fuel Sys1 Open1
Fuel Sys2 Open1

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 25 Old 10-28-2021, 05:47 AM
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Look at the electrode on the plugs, They are worn down(rounded). You need to replace them all!
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post #11 of 25 Old 10-28-2021, 08:01 AM
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Quote:
Originally Posted by V8GCZJ View Post
Look at the electrode on the plugs, They are worn down(rounded). You need to replace them all!
Spot on Matey

Last edited by Delta0; 10-28-2021 at 12:35 PM.
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post #12 of 25 Old 10-29-2021, 03:17 PM Thread Starter
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Thanks for the inputs, all.

These plugs are copper Champion 439s, RC12MCC4. They have about 17k miles on them. Put 100k on the Bosch platinums I had in there before ...

The Actron is all I have for checking codes, I cannot check pending or history. Getting to a real scanner is a problem, she really does not want to run.

Compression test showed 0psi on #1, the rest were 115-160 psi. Removed valve cover, found the rocker arm on intake valve #1 had popped out. Valve appears to be stuck open. Cam lobe has some marks, head body has some marks. Pics attached.

Could it be a dropped valve seat? Does this kind of thing happen in the middle of a highway run? She has never overheated but she has been flogged on a few occasions lately.
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post #13 of 25 Old 10-29-2021, 04:03 PM
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Is that the #2? Mine dropped a in intake valve on the #2. Yours looks like it's the exhaust. Sucky, I have a parts jeep I'm tempted to fix. If the valve sits lower then yeah it dropped you can tell by comparing it to the next piston over.
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post #14 of 25 Old 10-29-2021, 04:42 PM Thread Starter
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That is cylinder #1. Since the fuel injector is directly above the valve, I figure it must be the intake. Looks to me like it is sitting lower than the rest but I did not measure. I slipped the rocker back in, there is a LOT of room between the roller and the cam. Lash adjuster only has ~20k miles on it, pulled and inspected, seems solid idk. Seems pretty clear to me that the valve is sitting low, what else could cause that except a dropped seat?


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post #15 of 25 Old 10-29-2021, 05:54 PM
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Here's my 300000 km 02 laredo. Shameful it dropped looks so clean. Excuse the dust that was me. Was the passenger side but whatever the heads are coming off anyway.
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