QuestionQUESTION: I have owned this vehicle for a week and I washed it like 5 times already. After the fifth time at a different carwash I drove about 1000 feet and all the sudden it started misfiring severely. I took it straight to the shop. On the way there it seemed to perform fine at 60 to 70 mph at heavy acceleration but as I slowed down or proceeded uphill if I accelerated it would lose power and begin to shutter. I noticed a sound in the front left lower area that sounded like a popping sound. My guess is bc of the misfire it was causing the motor to be out of sync with transmission? My primary concern is this: I have had the service tech replace plugs wires, coil pack, valve gasket, upper plenum gasket, intake gasket, ecu was checked for water damage and swapped out, engine fuse box was switched out, compression test were done and passed fine volume test fine as well fuel pump is ok. The computer he has is showing low compression in cylinder 3 still. all others are fine. He is at a loss and cant seem to figure it out. he has hooked it up and there are no more codes anymore however the motor isnt running correctly. Side note: I did have the rear moonroof open and it rained inside and water seemed to pool up around the moonroof switch. The switch never worked prior but just a thought.ecu had no apparent water damage. I suggested checking out the injectors for clogs. I need your expert advise on misfire troubleshooting steps even though no check engine light is coming on.Upon misfire i promptly drove it 77 miles to my land rover specialist its been sitting there since last Thursday. HELP???? lol Thanks alot! ps i have all service history records and it has been impeccably maintained. Head gaskets were even put on prior to my purchase. It was a local trade in for a new one 2 owner truck.
ANSWER: Hi Joe,
my first thought was headgasket failure but your notes say it was replaced before you bought it. It's currently sitting at your LR shop? Drying out perhaps? Myself, I've never washed inside the engine compartment - too risky. I've seen too many problems resulting from that so I shied away from ever doing it. Dry clean was all I did.
Usual signs of headgasket failure is exactly what you describe, especially under load or in humid conditions. A real puzzle here.
Maybe its the harness to the ECM, more specifically, connector #3, C0636 - and pin #27. Maybe you can try drying the harnesses out and taking a closer look at pin #27 above, for cyl. #3. This harness is the weakest link in the entire chain of engine management system. This is the largest connector with 52 pins and if water should get into this...oh boy. Electrical corrosion is a problem for LR's.
Don't forget to also consider your a possible fuel feed problem to #3 cyl.
Best of luck,
JohnMc
---------- FOLLOW-UP ----------
QUESTION: If it is a fuel feed problem to cylinder 3 then what part could be the culprit? Is there a way that i can check to see if they actually did replace the head gaskets? Also, some progress as of yesterday: Tech said that his computer is showing 0 response to Oxygen Sensor. His remedy: replace with used one from another vehicle (LR). Still showing a fault on his computer tester. So he tried replacing the wires from ecu to o2 sensor and still no fix. That was 2 days ago and he hasnt called since and I cant get through to him. I'm not sure where we stand so I have to assume its not fixed as he still has the LR. Your thoughts on o2 sensor or more advice on original question?
AnswerHi Joe,
I have a question: did you wash the engine compartment? Just a 'heads up' : don't wash the engine compartment. There are electronics there that can fail and cause all sorts of trouble for you. For example, the CKP sensor (crankshaft speed and position sensor) is vital to the engine management system. IF it should get wet you could have problems exactly as you describe - difficult starts.
"The CKP sensor is located towards the rear of the engine below cylinder number 7, with its tip adjacent to the outer circumference of the flywheel. The CKP sensor is the most important sensor on the vehicle and without its signal the engine will not run. The signal produced by the CKP sensor allows the ECM to determine crankshaft angle and speed of rotation. The ECM uses this information to calculate ignition timing and fuel injection timing."
To determine headgasket failure you should have your a cylinder compression test or the exhaust monitored for coolant contamination. To check if the work was done, you would need to open up your engine to expose the area - not an pleasant DIY job.
If it was a HO2 (Heated Oxygen sensors) it would usually trigger a MIL code (check engine) and not affect just one cylinder but an entire bank.
It could be a problem with a particular cylinder fuel injector - namely #3. You could have your mechanic check the resistance of any fuel injector from the ECM:
Cylinder No 1 - pin 41 of connector C0636 of the ECM multiplug.
Cylinder No 2 - pin 1 of connector C0636 of the ECM multiplug.
Cylinder No 3 - pin 27 of connector C0636 of the ECM multiplug.
Cylinder No 4 - pin 40 of connector C0636 of the ECM multiplug.
Cylinder No 5 - pin 2 of connector C0636 of the ECM multiplug.
Cylinder No 6 - pin 15 of connector C0636 of the ECM multiplug.
Cylinder No 7 - pin 14 of connector C0636 of the ECM multiplug.
Cylinder No 8 - pin 28 of connector C0636 of the ECM multiplug.
Using a multimeter, you can check the resistance (normal: 14.5 ± 0.7 ohms at 20 °C (68 °F).
Hope this helps,
JohnMc
