Emissions (?) - 2002 Land Rover Discovery II SE
Posted by 1720000@reddit | projectcar | View on Reddit | 6 comments
Good evening, All,
I recently purchased a 2002 Land Rover Discovery II SE (4.0L V8 / Auto) with 111k Miles. Epsom Green over Bahama Beige. It had some known issues upon purchase and I’m working my way through them now. Details to follow with a more informative document uploaded in the photos.
SERVICE ENGINE SOON light(s) indicate that there is some issue with fuel mixture, it’s running too lean. Initial codes read issues with O2 sensors and the air/fuel mix.
Original Codes:
P0174, P0150, P0140, P0141, P1171
Google had a lot of recurring themes so I started there. Replaced MAF with Duralast brand (easily available…) and the two downstream O2 sensors with OEM Bosch.
I have the two upstream O2 sensors but I can’t access the pigtail connectors in the engine bay so they have not yet been replaced.
Post-install of MAF and downstream O2s, it ran better initially. 100 miles later, lights back on, not much performance change.
New Codes (Post MAF & Downstream O2 Install):
P0174 (Repeat), P0150 (Repeat), P0130, P0441, P0300, P0304, P0171
New codes indicate that both Banks 1 & 2 are still running lean. They also indicate there is an issue with Cylinder Misfire(s), specifically Cylinder 4.
Thoughts Moving Forward:
Spark plugs, ignition wires, ignition coils/packs, fuel injectors, purge valve.
CarFax records show that it failed emissions inspections 4 times in a row… But that was in Texas and it was 4 years ago. It also says valve cover gasket(s) were replaced in May 2022 at approx. 108k miles. It does NOT say anything about the items I mentioned moving forward.
Just for fun… At time of purchase it included:
Front & Rear Steel Bumpers
OME Suspension
HD Steering & Control Arms
Brand New BF Goodrich KO2s (WAY Too Big)
russdiculous@reddit
I love Discos but don't think I'll own another one. It's always fix 1 thing, and next time you drive it, 3 other things break or rattle loose. Engine related parts are available enough at least, it's the interior and body parts that are only available at exorbitant prices or used/salvage.
texan01@reddit
Vacuum leak or air leak I. The intake can raise all sorts of havoc on running lean.
Fermentatorist@reddit
Thats not just a car, thats a transporter of the gods...
https://youtu.be/fT41ARny4VY?si=ktNWbAjBVDPsNTOl
skudbeast@reddit
If it's running smooth with no misfires, why would you replace all the ignition components?
It has to do with a/f ratio, so coolant temp sensors, air intake temp sensor, vacuum leaks, fuel pressure regulator...
I had one like yours, had the 3 amigos and a blown head gasket at the same time and traded it for a c1500 Chevy. Never buying land rover again, but it was nice to drive around for a bit. Id recommend changing a few cheap sensors and then just look into a classic plate or mileage exemption if it doesn't pass, this is a money pit imo...
1720000@reddit (OP)
I’ve owned it for less than a week so I’m not quite ready to move on yet… I’d like to at least get this issue diagnosed and potentially resolved based on costs.
It does have a misfire in Cylinder 4.
I have replaced MAF and Downstream O2s for relatively cheap.
I think I will be getting both a compression and vacuum leak test(s) done because that was a recurring theme amongst the codes during my research.
I was considering plugs, wires, and injectors because if I’m in there then I might as well do it all at once so I don’t have to get in there again. I don’t know the history of the plugs and at 111k miles and 25 years old it can’t hurt.
My typical “new” used car plan of attach always includes all fluids, filters, belts, and plugs anyway… Just so I have a baseline to work off moving forward.
skudbeast@reddit
I agree with some of the sentiment, but with cheap and counterfeit parts I would be very careful about the parts cannon, you could put something on that makes it worse and causes even worse diagnosis. Check for vacuum leaks, ensure proper fuel pressure, and so on. Also misfires can very easily be vacuum or fuel related not ignition especially on an older engine that is very, very prone to head gasket and compression related issues. Good luck.