Hello people,

I'm having some problems with my 2004 Discovery and would appreciate some advice before taking it in to a mechanic. For several months now, I've had the codes P1171 and P1174 popping up (used to be more codes, but those are the current ones).

My most recent attempt to get them to go away was replacing both front Oxygen sensors with Bosch O2 sensors from Advance Auto Parts, but no luck. They came right back.

Here are a few symptoms:

- When starting up, engine revs real high and then kind of guns the engine up and down until I put it in reverse, when it stops.
- Rough idle, hesitates when accelerating sometimes.
- Engine knock (or click?) coming from top area of driver side valve cover I think?
- Seems like there is a very slow oil leak, possibly around driver's side valve cover

Here are a few things I've replaced within the past 6 months. (Some are related to this issue, some others are not):

- Replaced Mass Airflow Sensor (MAF)
- Replaced front O2 sensors twice with Bosch model
- Replaced Throttle Position sensor
- Replaced heater plate and several coolant hoses to stop coolant leak
- Performed Seafoam treatment

Not sure how to embed a video on here but here's a YouTube video of the knocking issue:

 

Those codes are for vacuum leaks/unmetered air entering the system. If you have ultra gauge or scan tool you can read your fuel trims and confirm this or simply use brake kleen with a straw and spray all areas around plenum and vacuum lines. Also spray your injectors. You can reach injectors 1-4 with straw. Be very focused with your sprays and take note if engine begins to stall, this will be your indication as to the leaks location. In my case it was the orings which seat the injectors in their ports that were bad. Simple cheap fix and have been gone since. Orings and the connections around the MAF and plenum seem to be the most common spots other people have found leaks which trip these codes.

 

You most likely have a Vacuum Leak. It can be anywhere after the MAF (injector O-rings, plenum gasket, cracked intake tube, loose hose clamp, and on and on). I had the same codes and found the leak by doing a smoke test. You can go get a smoke test done at a repair shop or you can do it yourself at home if you feel up to it.
Check out my Thread "How to smoke test with a cigar", it's helped many people find there Vacuum Leaks.
https://landroverforums.com/forum/di...s-cigar-54235/

 

faulty IACV? try my high idle fix. or testbook. either corrupt values in ecu or bad iacv.

 

Thanks for the tips guys, I appreciate it. I think it is a vacuum leak of some sort so I'm going to try spraying the brake cleaner and the cigar trick to diagnose where the vacuum leak is.

I think I'm going to get one of those Ultragauges. Can you leave one of those plugged in all the time? Or is it just a diagnosing tool?

 

When you get the ulatrgauge you can leave it in all the time. The tool is used to check and clear check engine codes but it also monitors your engine temps. The loud ticking you are hearing is likely your engine sleeves. Over time they come lose because they were not properly fitted to the block from the factory. The heat cycles warp the aluminum block engine causing it to expand and contract and eventually the sleeves just come lose and make the ticking noise you hear. Most Discovery 2 models have the same problem especially later models 2003 and 2004. These are great trucks but the engine is the downfall. You can have the sleeves secured again to stop the ticking. Might as well wait until its time to do the head gaskets.

Is that a Range Rover I see in front of your Disco? lol If so I bet the driver was frowning about your ticking Disco haha

 

Thanks you! and thanks to dmatranga . I was going to post a video of my disco, making the exact same noise. I think you have two problems, 1 your codes and 2 this ticking issue. Pretty sure TRIARII hit it on the button. Now I know what to do/wear to start.

 

Thanks for the tips. Haha yes TRIAR, it was a Range Rover in front of me. They seem to be all over Houston these days. And that ticking noise is embarrassing for sure; makes me feel like I'm driving a, in the words of Adam Sandler, "piece of **** car".

I'm going to look into getting a quote on having the engine sleeves refitted (and head gaskets). Last time I checked it was going to be somewhere around $2,500, which is pretty ridiculous. Not sure when I'm going to be able to do the repairs but it's good to at least know what the problem is.

 

Still trying to troubleshoot these issues before taking to a mechanic. Current codes are <b>P1171, P1174, and P0305</b>.

On cold starts, it still revs up and down while in Park, so I'm still not sure why that's going on. Any other suggestions?