Misfire codes 2006 LR3 4.4

[Ellis B]

My 2006 LR3, 4.4 V8, developed a misfire a while back, about 8 months ago, at first the codes read cylinder 3 and 5 were misfiring, so I change all the plugs and the two coils on cylinders 3 & 5, that helped but she still seemed to run a little rough. The LR is my wife's DD, it has now started running worse, and if you accelerate hard the check engine light flashes and she has no power, when I hook it to the computer it reads misfire on start up within the first 1000 rpm and cyl 3 and 4 misfiring, I decided to change the rest of the coils and I checked the plugs for any problems. # 4 was not firing. it had a total of 12 misfire codes before I changed the coils and the plugs again this time, I cleared the codes and started her up , she is still misfiring and the diagnostic tool is reading 5 codes:
P1368 - ignition sys circuit malfunction / probable cause wiring / coil
P0352- IGn coil B Primary secondary circuit / probable cause wiring / coil/ ECM
P0353- IGn coil C Primary secondary circuit / probable cause wiring / coil/ ECM
P0355- IGn coil E Primary secondary circuit / probable cause wiring / coil/ ECM
P0358- IGn coil H Primary secondary circuit / probable cause wiring / coil/ ECM

any suggestions or thoughts would be greatly appreciated

she now has 8 new coils and 8 new Plugs

 

[jpc1818]

Have the same problem with mine, would love to get an answer...

 

[ColoDisco]

Check the wiring at the ECM and all connections to the ignition coils for corrosion or broken wires.

 

[Victory_Overland]

Check the wiring at the ECM and all connections to the ignition coils for corrosion or broken wires.

When I started my truck after an accident I had every code known to man. I had some misfire codes like you, I swapped around the coils to see if it followed and it seemed intermitent at best. I disconnected all connectors, cleaned them, dielectric greased all, reinstalled and went through the ECU code clears and calibrations.

I did the recalibration on the ECU (All of them) with my GAP Tool and once it was complete and codes were clear, no further problems.

I would guess you have a connector/wiring corrosion problem like ColoDisco stated. Considering you have known good coil packs and plugs and the problem seems to move around, I would stick to ECU and wiring around those areas.

 

[Ellis B]

Thank you all for the input, I will start checking the connections at the ECU, and the coils as suggested.

Is the ECU located behind the passenger kick panel on the LR3?

 

[jpc1818]

Ok so I have figured my misfire issue out, this may be a slightly winded explanation.

So I was getting the lean bank codes (PO174/PO173 I believe) for both sides last year, so I picked up a used OEM MAF sensor and it went away so I could get it inspected. Following the coldest day we had last year, the truck was running like crap and the CEL came on. I was getting misfires on 1/5/6 cylinders. So I took the truck to several mechanics and the dealer with no fix...below is a list of the things that I changed:

-New plugs
-New coils (8)
-New PCV
-Cleaned the injectors the BG
-Smoke test
-Hours on the computer and still CEL

So I pulled out the intake and found a pretty large amount of carbon on the intakes of the misfiring cylinders.
I removed some of the carbon with a shop vac.
I then picked up seafoam, added it to the oil, fuel and directly into the intake (after the MAF sensor).
I injected three bottles into the intake, 1/3 at a time, ran for 20 minutes/shut off for an hour, then repeated.
My misfires went away, and the intakes are sparkling clean!
I was then getting the Lean bank codes again.

This got me thinking about how to proceed and why the carbon buildup happened in the first place.
This must have something to do with the lean codes.

I then bought the GAP II OBD tool.

Upon plugging it in and reading about how it works, I ran diagnostics on the engine and the Map Manifold Air Pressure Sensor was giving a crazy reading, as if the truck was @ 45k ft above sea level.

I picked up a new MAP sensor from the dealer and the CEL went away and the truck is running awesome..

In other words, after spending countless hours and a ton of $$$, the root of the problem was a $100 MAP sensor.

I hope this helps anyone that has the same problem.
BTW 251k miles on the original 4.4 motor at this point.

 

[Victory_Overland]

Stoked the Gap worked out for you. That thing is worth every penny and usually pays for itself on the first use.

Congrats.

 

[ColoDisco]

Great follow up information! THANK YOU! Most threads like this end with no resolution. Just curious, what is your MAP reading now that it's normal?

 

[jpc1818]

I don't remember the exact number offhand, I just know it was much less. I also decided to update all of the ECU software...
What a difference, engine is running much smoother.
Very happy to have this old girl back from the dead.

 

[Victory_Overland]

I don't remember the exact number offhand, I just know it was much less. I also decided to update all of the ECU software...
What a difference, engine is running much smoother.
Very happy to have this old girl back from the dead.

Did you do all of the gearbox calibrations too? I seriously gained 1-2 legit MPGs after I recalled and updated everything.

Great feeling.

 

[proper4wd]

Im glad you figured this out and I just want to say bravo for actually diving in and diagnosing/fixing the problem like a professional rather than just throwing parts at it or giving up.

Carbon buildup in the intake is a common issue on nearly all late model engines - it usually has to do with an extremely aggressive PCV system in my experience. Check to make sure that system is operating as designed also.

 

[Ksasr107]

Ok so I have figured my misfire issue out, this may be a slightly winded explanation.

So I was getting the lean bank codes (PO174/PO173 I believe) for both sides last year, so I picked up a used OEM MAF sensor and it went away so I could get it inspected. Following the coldest day we had last year, the truck was running like crap and the CEL came on. I was getting misfires on 1/5/6 cylinders. So I took the truck to several mechanics and the dealer with no fix...below is a list of the things that I changed:

-New plugs
-New coils (8)
-New PCV
-Cleaned the injectors the BG
-Smoke test
-Hours on the computer and still CEL

So I pulled out the intake and found a pretty large amount of carbon on the intakes of the misfiring cylinders.
I removed some of the carbon with a shop vac.
I then picked up seafoam, added it to the oil, fuel and directly into the intake (after the MAF sensor).
I injected three bottles into the intake, 1/3 at a time, ran for 20 minutes/shut off for an hour, then repeated.
My misfires went away, and the intakes are sparkling clean!
I was then getting the Lean bank codes again.

This got me thinking about how to proceed and why the carbon buildup happened in the first place.
This must have something to do with the lean codes.

I then bought the GAP II OBD tool.

Upon plugging it in and reading about how it works, I ran diagnostics on the engine and the Map Manifold Air Pressure Sensor was giving a crazy reading, as if the truck was @ 45k ft above sea level.

I picked up a new MAP sensor from the dealer and the CEL went away and the truck is running awesome..

In other words, after spending countless hours and a ton of $$$, the root of the problem was a $100 MAP sensor.

I hope this helps anyone that has the same problem.
BTW 251k miles on the original 4.4 motor at this point.

Hello jpc1818 can I ask you please do you have a video or photos of how you cleaned the intake ? And how did you change the map sensor , also how can I update the ecu software ? Thank you very much of how you explained everything .

 

[Ksasr107]

Hello proper4wd I have a leaking PCV , I tried to take it out but I couldn't , I removed the two screw but could not remove the hose and the wire bundle ? Can you tell me please how to disconnect it and clean it ! Thanks

 

[Ellis B]

Thanks for the information, I am still dealing with my issue, but this gives me more to work with.

 

[robbing23]

Thanks for the information, I am still dealing with my issue, but this gives me more to work with.

Ellis, did you ever figure out your problem? I have the same exact codes so I'm hoping you did.