Hi All,

I did a lot of research on the forums to try and find solutions to a few different issues I'm having prior to posting a new message. I began writing separate responses in existing threads to my individual problems, but something tells me that some or all of them may be related. Hopefully the title of this thread will help future research; I promise to report back a successful diagnosis if we find one!

I have a similar noise as described by real_tea in this thread: https://landroverforums.com/forum/di...erating-45958/, appearing right around 70mph. It is there under acceleration and cruising, but if I let off the gas it goes away. At the same time as the noise first presents itself I also get a high frequency/low amplitude vibration in the seat (not in the steering wheel), seemingly from the drivetrain. It is also there under acceleration and cruising but dissipates when coasting. I am ALSO battling a P1171/P1174 code issue. I originally thought these were all separate issues, but I am beginning to think some or all of them may be related.

I purchased the vehicle (04 Disco II HSE) with all of these problems, so I don't have any history prior to about 3 months ago. Since purchase, I have:

• Replaced the front drive shaft with a Tom Woods model from AB
• 4 wheel alignment/4 wheels balanced
• Replaced all 4 O2 sensors
• Replaced all Trans/CDL/Diff Fluids
• Upgraded to K&N filter
• Replaced valve cover gaskets
• Replaced intake manifold gasket

The whistling has been there since I got it. I originally thought it was stereo feedback from the aftermarket XM antenna, but it doesn't present under acceleration in lower gears or cruising at lower speeds. The P1174 and P1171 codes did not appear until about 650 miles after I did Disco Mike's major maintenance, which included the K&N air filter, new valve cover gaskets, and new intake manifold gasket. My mechanic thought it might be oils from the K&N filter that plugged up the MAF, but we cleaned it and the codes came right back.

The tires are relatively old and the front two show more wear than the rears. The driver's front tire has excessive wear on the inner edge due to poor camber when I got it. They're on my list to replace. I have new transmission and motor mounts on order, as well as a new rotoflex on the way.

So is the whistling actually a vacuum leak that's also causing the P1171 & P1174 codes? Or is it related to the vibration I'm feeling? Or are all three independent? To make matters worse, in the state of TX I can't get it registered in my name until it has passed inspection, so I am driving on expired temp tags and the title is still in the PO's name as I try to fix this mess. Any help you guys can provide would be greatly appreciated!

Many Thanks,

Jason

 

vacuum leak that's also causing the P1171 & P1174 codes


my guess^

 

I would agree with dusty1, check for vacuum leaks.
I don't know how likely it would be to hear a vacuum leak at higher speeds. The engine loses vacuum as the rpm rises. So you're much more likely to hear a leak at idle when the vacuum is strongest.

If the vibration is speed specific, it's likely just a tire out of balance.

 

Thanks guys, for the input. I am going to see if my mechanic can do a pressurized smoke test this weekend or may just try the carb cleaner method if he's not available. I'll report back if I find a vacuum leak.

 

Ok, I spent some time yesterday troubleshooting. Here's what we found:

• There are two vacuum connections which seem to fit loose, but when pulling vacuum through another connection in the same section of the vacuum system, both hold. One goes into the canister by the SAI filter/pump assembly, the other is opposite the canister on the end of the intake manifold. Otherwise, the vacuum system seems snug.
• I'm not positive, but I think I stopped hearing my SAI come on at startup around the same time as the P1174 and P1171 codes showed up. We are in the heat of summer here in Houston though, and I know the SAI is temp-driven, so maybe this is just coincidence.
• We tested a new MAF with no difference in results, so I don't think that's the problem.
• While out test driving to try to get it to throw the code, we noticed something else peculiar: my TPS reads 76-78% at WOT. If the computer is seeing more air than what the TPS says it should be getting, could that be my problem?
• While under the vehicle, we noticed the early signs of HG failure on the driver's bank. No mixing of oil and coolant, just a slight exterior leak of coolant. Yay.

So what say you guys? Could the TPS be the culprit for my codes?

Thanks!

 

I would definitely look at the TPS as a possibility. Although, I have seen vehicles where the WOT reading is around 80% or so.
So, I'm assuming you have a scan tool with live data? Try opening the throttle by hand and watch the readings on the scan tool. If it goes higher then it's probably not a TPS problem and you just need to adjust the throttle cable.

I didn't realize that your codes were P1 codes. I was thinking they were P0171 & P0174. I think those codes are pretty much trying to tell you the same thing, lean readings on the o2 sensors.
You could try checking that the o2 sensors are working properly by adding propane to the intake and watching the data from the o2 sensors to make sure that they go rich. Also, you can pull off a large vacuum line to make sure they go lean.

 

Get rid of that K&N before it kills your MAF. that was never on my Major service because of how it will effect your MAF.

 

Apologies Disco Mike, I did not mean to imply that you had the K&N filter as part of your Major Service; rather, those were additional items I did that I thought were pertinent to the conversation. I'll order up a new OEM filter with my next AB purchase.

We did track the TPS in real time. We found that it is reading 0% at idle, tracks increased % as I depress the pedal, and maxes out at 76-78%. We also checked that depressing the pedal all the way to the floor did in fact open the throttle body completely. It could not be turned any more by hand due to being seated against its wide open stop.

Good idea on the propane/vacuum lean/rich test. The next time I can get on the computer I will test that. I also did confirm that my SAI is still working, so that is not an issue.

So, looking like my TPS?

 

It's hard to say for sure. Does the voltage rise steadily all the way until it stops? Or does it get to 78% before the throttle plate is all the way open, then stay while you open it the rest of the way? If so, it may be defective.
You could try back probing the signal wire and use a multimeter to test the voltage. It should start low, maybe around .5 - 1v or so and should increase as you open the throttle. Most 0-5 volt sensors will top out somewhere around 4.5 volts. If it puts out anything close to that voltage range, then the 78% you see is probably correct.