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Discussion Starter · #1 ·
My 2003 Disco seems to have lost power. I notice it while trying to accelerate on exit ramps or passing (ie. going into overdrive). It is extremely sluggish and strains to go up hills. It feels like your pulling a trailer with a pallet full of bricks in it. Going up hills it shifts into overdrive and barely makes it. On flat services it seems fine and seems to run fine other than this very noticeable reduction in power.

Background:
- I have an Ultragauge and am runnin NO CODES!:)
- D2 has 111k miles with an engine that only has 35k on it.
- Has an ARB steel front bumper, rack and slightly oversized tires but I firmly believe this does not account for the significant loss of power
- Seem to shift fine
- I run 93 Ocatane gas and put Seafoam in about every three fillups
-New O2 sensors and MAF within past year
- No fuel filter to check


The only thing that has been suggested is that the Catalytic Converter is on its was out or clogged. My questions are:

1) Any suggestions beyond the Cat

2) Is there a way to diagnose this the Cat to see if it is bad?

- I have seen some videos of people drilling small holes on either side of the cat and measuring pressures to see if its clogged? Is this the way to go?

- Someone suggested taking the O2 sensors off and tie them up for a temporary experiment to see if the power restores after releasing some of the pressure before the cat. If so probably the CAT. Does that make sense in terms of a reasonable diagnostic?

3) If it were the Cat would it not give me some codes?

4)Would a muffler shop be able to tell if it is the Cat.

5) I understand I have 2 Cats off the Y so I would prefer to make sure its bad before shelling out the bucks.


I would really appreciate any help. If I cannot get it figured out before Friday she wont be able to join the family on the beach Vacation. I am just not sure I can do that to her.
 

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The description you give of the driving condition is exactly how I would describe a Disco with oversized tires. What size are you running?

The system should be providing CAT inefficiency codes if the CAT's are not functioning to spec. Yes you can remove the front O2's to test if a CAT is clogged. The only time I have actually seen a clogged CAT the engine was unable to rev to high rpms. Removing the O2 relieved the pressure and the engine could rev normally. Be cautious if you do this as things get very hot in the vicinity around where the O2 bung will be directing the exhaust.

A muffler shop likely would not disagree with you if you said you thought you had a bad CAT. Would be bad for business...

You can place a pressure gauge in the font O2 bung to see if there is high back pressure. I have rigged one up using a brass barbed nipple and a vacuum gage. Don't run it long as you will melt the gage.

Since you have an Ultragage, inspect the Long Term and Short Term fuel trims. See if those are creeping to one extreme or another. Could be at the edge of MAX / MIN but not enough to trip a code.
 

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I would agree with belew. My rover with oversized tires handles the same way. How long have you been driving with those tires? Is this a recent problem? I have found my DII shifts better in sport mode. Maybe try that and see if holding the gear longer would help.
 

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Discussion Starter · #5 ·
The problem definitely developed after the tires so although it may be aggravating it something else is at play.

Went ahead and dropped off the truck at the Rover mechanic. I did the test drive with him. He thinks it is transmission related but he wants put it on the computer before diagnosing. Crap, new engine, new transfer case and now the transmission. I did not connect the power loss under load with a transmission issue. Man I hope its not worse case!
 

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Sound like plugged exhaust to me
 

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This is some what of a lost art now days, but in the days of old.. It was common practice to use a vacuum gage to diagnose and troubleshoot engine issues. Here are a couple of charts. One shows what to look for with a restricted exhaust. May not pinpoint your issue but might help rule out a suspected one.
 

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Discussion Starter · #9 ·
Brought it to my Land Rover Mechanic who has the Land Rover Computer and he said it was showing misfires once it reached 2500 RPMS and said unless it continues misfiring that the computer will not store the code. Mine turned out being the plugs not the wires which were relatively new. I had put in Bosch Platinum Plus 4' plugs about 18 months ago and they were the culprit. My Land Rover Mechanic said they were the wrong plug and replaced them. The main lesson learned here is that just because my ultraguage is not showing codes that does not necessarily mean there is not a misfire happening.
Well, $200 later he turned out to be wrong as now I am pulling misfire codes when it gets on the highway. Again at high RMS which is what I am thinking the whole power issue is relating too. Reset the codes and have not come back but I have not brought out onto the highway either where it takes the pedal all the way down to get it to 60. I went ahead and took off the front O2 sensors for a test of the catalytic converter but did not notice any power improvement. I had put on new STI wires two years ago so I don't think it is the wires. So is the only thing left to consider the coil pack? Is there a way to test or is it just a process of elimination? How difficult of a job is it? Thanks for your help!
 

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Misfires only above 2500 RPM.. If plugs and wires are good, My money is on a flat cam. Been there. Went threw the entire system Plugs, Wires, Coil Packs, Wiring Harness. Still only miss-fired at high RPM's.

Take a look at the live data on your Short Term Fuel Trims (STFT). Everything looks normal below 2500 RPM? Raise RPM's above 2500 and hold. Does STFT drift out of range on only one bank? Does O2 Sensor on that bank drop back to open loop?
Where is your Long term Fuel Trim (LTFT) at?
 

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Sounds like I'm in the exact same boat as you. I too am experiencing a huge lose of power above 2500 rpm's and get engine misfiring codes.

I had replaced my plugs and wires 11 months ago with E3 E3.48 Spark Plugs & Kingsborne 8mm wires. I also have 265/75r16 tires and just ran through a tank filled with BG 44k. No change and not sure what to try next.
 
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