My LR3 is a 2006 SE V8. I replaced spark plugs and cleaned the throttle body as advised. Still is sluggish and slow to respond at low RPM's. If I let off the gas or want to pass I have to put it in sport or manually downshift to a gear that gets it over 3k rpm to get any acceleration. Down low it is a dog. No power at all. It is really irritating because I really have to mash the gas to get going if i am already rolling. from a stop it launches hard at 25% throttle but anything more than that and you can feel amiss and a sound like an exhause leak/incomplete combustion. When it upshifts to second it takes forever to get up to speed, even at full throttle because it won't kick back down to first after about 20 mph or so and the power is very weak until it wakes up at around 3500-4000 rpm. My Disco II throttle so much more responsive but of course at wide open throttle can't match the LR3. It even sounds ugly when I get on the gas from a stop or when I give it moderate or greater throttle below 3,000 rpm. Almost like an exhaust leak and you can really feel the shudder, especially if I select manual and 6th or 5th gear below 3,000 rpm. if I am very light on the gas it will accelerate, but if I push it more it starts shuddering and will not accelerate unless on flat ground. When I select drive and hold the brake and stab the throttle you can feel and hear the miss. If I am light on the throttle the truck squats and you can feel that it has power, but after about 20% throttle it sputters and is weak. Funny thing is when my battery went bad and I had to replace it, after replacing it the problem stopped for a day or two, and come back. This thing was quite peppy when I first got it and had great low end torque. Now it has no low end torque and fuel economy sucks. My OBD II scanner will say 8 codes found but when I select read codes it says no codes found. Guess I will have to go to my local european car mechanic and have him put it on test book because I am stumped and this this is very frustrating to drive, especially since every once in a while it will run right for a short time, also it runs much better right after the first startup in the morning before the engine warms up.

 

That's a lot of good information, unfortunately, those fault codes would be a great help.

It being better when it is cold, and right after changing the battery(which resets adaptions) would suggest the issue lies in engine fueling, or spark control.

It running good at high rpm/high load would suggest fuel pressure is fine.

So just on that, I would be looking at sensors (MAFS the most) vacuum leaks, checking the intake for any standing oil, and probably tossing a new ignition capacitor on it just for fun.

5th and 6th gear are never going to give much acceleration just due to gearing.

Maybe swing by a parts store and see if their scanner can read your codes before taking it in.

Guessing this was happening before the new plugs, if not, what plugs are you running now?

There are several other possibilities, from bad sensors in the throttle body, to plugged up cats, but most of these are somewhat uncommon, and don't fit your description fully. If you can get the codes (and even more importantly, the Adaptive Fuel Trims, but you'll need someone with an IDS/SDD to get that) report back, and we can try and figure it out then.

 

My check engine light isn't on, but my generic scanner said 8 codes, but when I select read codes it says no codes stored. Also, even when I hold the brake and push the accelerator, once I depress it more than about 10% you can feel it shudder and the rpm's drop slightly. Are the coil pack boots replaceable? I am wondering if a coil pack boot is bad and spark is arcing to the tunnel walls. I bypassed that noise filter thing and it still shudders. Also, can you clean the MAF with CRC MAF cleaner? I know those things are sensitive and I would never try it unless it is safe. I am thinking of running a couple tanks of BG 44k and see if that helps. Otherwise to the european car repair shop it goes. This is so annoying. Even when I want to pass someone, it takes forever for the transmission to kick down and respond. It literally has taken 2 whole seconds from when I mash the gas for it to kick down and start pulling. the vehicle is very unresponsive unless I am in manual mode and the rpms are at 3,000 or higher. once it hits 3,500 rpm it feels like a small boost of power kicks in and it starts pulling harder. kind of reminds me of the older hondas where you could feel the vtec kick in like a turbo or something. If I am easy on the gas it drives smoothly but when I want to change lanes and go around somebody or pass it is an issue.

 

You can't read it with a generic scanner most likely. Is there some particular reason why you can't take it to a shop. It could be anything from a vacuum leak to a blown head gasket or gummed up valves, fuel pump, etc. It seems like an odd problem, but you really need to get it on a system that can read codes (if it's even throwing a code).. I'm wondering if it could be tranny related, engine related, transfer case related.... it's really hard to say.

I was chatting at the dealer recently and it was mentioned that a lot of them are coming in lately with badly gummed up valves, so bad valves are not closing, etc. So they are doing a BG cleaning service of some kind. I'm not having trouble like that yet, but I'm going to pay them to do it for me.

 

The valve build up issue is much more prevalent on the 10 and up, with the DI 5.0. But yearly induction services, and an injection service once every 60k or so really will keep the Jag engine in great shape. Can't tell you how many customer's I've had surprised at how well the engine should run after doing this and a tune up.

But you touched on a very good point, I could see this being something trans related, which your scanner may not display.

Whatever this ends up being, it is not a common issue, and may need proper diagnosis.

 

Some of the BMW guys have noticed sluggish shifting of these 6hp26 transmissions. Many times they have been able to fix the issue by replacing the solenoids. I guess there are kits available that come with all of them. I'm not sure how hard it would be to replace on a lr3, because you have to remove the valve body, and on an lr3 you cannot even remove the pan without a lot of work. Maybe the valve body would come out easier?

http://www.bimmerfest.com/forums/sho...d.php?t=654634

 

In the early days of LR and the 6HP26, and it's notorious leaks, I did that a few times. You can get to the bolts that hold the valve body in with the pan dropped, but not removed, and once the valve body is loose, the pan comes right out, with out the need to remove exhaust or cross member.

However, there are seals between the valve body and the trans itself, which if great care is not used, can be damaged, or misaligned.

I'll put it this way, I remove the exhaust and cross member now, as have for many years, as risk vs time saved is not enough to make it a very viable shortcut.

Once the pan is fully removed though, the valve body comes out in a matter of minutes. Care still needs to be taken when re-installing, and those seals should be replaced whenever separated, according to LR at least.

 

So, just to recap the OP's concern, there are two issues...

1. The engine falls on its face when pushed from a lower RPM.

2. There is a delay in down shifting.

Did both of these occur around the same time?

Is the lack of power at all speeds, or only when in a higher gear?

If you put it in manual 1, and give it say 50% throttle from a rolling start, does it take off, or would this cause it to 'studder' as well?

When it is 'shuddering', does the engine speed increase, as if the trans (torque converter) is slipping?

If engine speed does not raise, and it only gets up and goes once at a higher RPM, regardless of selected gear, I would be looking at either a large vacuum leak, or a bad MAFS(cleaning may not be enough, as the only part that gets 'dirty' is the IAT sensor bulb, which I don't see causing this dramatic of an issue. Both of these should be setting the MIL on, and throwing codes. If nothing else, try another scanner.

Other possible cause for the above scenario would be a (or multiple) misfires, again, should have codes, and a misfire like this is not that common on this engine.

You're at the point of throwing a part at it, or having it diagnosed, I would choose the latter.

 

I agree with the latter.. If after diagnosing it turns out to be the transmission, let me know.

 

I know its the engine because I can hear and feel the misfire and can feel the power loss. When I put it in manual 1, hold the brake amd apply light throttle it revs up to the torque converter stall rpm smoothly. When I add throttle input or mash it there is less power (and requires less brake pressure to hold the vehicle). I figured it would throw a code. I've even purposely shifted intoba higher gear like 5th or 6th manual mode and floored it after the torque converter locked and made it misfire, hoping I could get it the trigger the CEL so I could determine if it were a random multiple cylinder misfire, or a misfire in a specific cylinder. I could take it tk a shop but where's the fun in that. I am persistant and hard headed which works to my advantage sometimes, and sometimes not so much to my advantage. I want to solve this problem without having to take it to the European shop (which is a very good shop I might add) and I certainly am not going to throw parts at it. Ill take it and get the ecy scanned. The Eurotek only charged $35 last time when I had my ABS codes scanned and cleared after fixing the 3 amigos on my Discovery II.