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2012 Land Rover LR4 has an undiagnosable acceleration issue


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whydibuythis
Novice

Feb 24, 2023, 4:54 PM

Post #1 of 12 (887 views)
2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

My 2012 Land Rover LR4 HSE, 5.0L V8, 120k Miles...

...is an awesome vehicle with an awesome list of problems at the point of purchase (used) and I've taken care of most of them. One problem remains and despite the time spent with mechanics, I've been informed I'll have to live with it until something else happens to give us a better clue.

Depress the accelerator like a grandparent and it gently accelerates, moves through the gear array like you'd expect.

Depress the accelerator like a sociopath and it flies, shifts mostly as god intended with a rough spot or two, approximately at 3rd gear or so. Can't be too sure.

Now ...try driving like the rest of us and:
Smile 1st gear, normal, strong acceleration
Smile 2nd gear, same story
Unimpressed 3rd ...bogs down, almost like its gone into crawl mode and it feels electronic (consistent and sudden, no concerning noise). It meanders through RPMs until 2100 and the tach hunts briefly. It reaches 3200 RPMs and without any change in throttle position, the engine comes to life and it takes off in a manner I'd expect considering engine size, horses and weight.
Smile 4-6th gear, it accelerates as it was designed to.

It has no check engine light, it throws no codes. The transmission has been rebuilt, torque converter replaced and checked a 2nd time. Smoke test? It passed. Throttle body was dirty, it was cleaned, twice (2 different visits to a European auto mechanic), no change in symptoms. Spark plugs have been replaced. Scoping once the spark plugs were removed shows some clean spots in cylinders 7 & 8 but I get no white smoke and I haven't had to add coolant once, not since it was purchased 6 months ago, so no dice there (probably?). Driving while connected to the computer yields nothing. At all. Compression is good, fuel delivery, fine, etc.

Potentially related though just as likely inherent to the vehicle: at highway speeds, if I decide to accelerate by depressing the throttle a bit more, I get very little acceleration, but when I go heavier, it drops gears, RPMs are always above 3000, and it gets me to where I want to be in the manner I expect it to do so.

The engine does have a tick, audible from the sides of the vehicle, and bottom, but not from the front or top of the engine bay. Probably a sticking riser, but I'm not likely to rebuild the engine for that unless I have to. An engine flush was done, because why not? It never works, but I did it.

Help. What could be causing this? If you think it's mechanical, I get it, but it is powerfully consistent, regardless of temperature, conditions and my driving behavior. It truly seems like an electronic issue. But I'm no better than a brand new mechanic so beyond possible I don't know what I'm taking about there.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 24, 2023, 5:08 PM

Post #2 of 12 (884 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In


Quote
2012 Land Rover LR4 has an undiagnosable acceleration issue -


That's just simply not true. Anything can be diagnosed as long as it presents itself.

The problem you have is the mechanic are not willing or just not capable of doing what it takes to find the problem.

You have a Land Rover. It was just rated the most unreliable vehicle made and requires a highly knowledgeable technician that is equipped with the right equipment. If you are dealing with the local general repair shop, you likely won't get your answer. You need either the dealer or an independent highly experienced in Land Rover.

This won't be cheap but if you're going to drive a Land Rover, you have to be prepared for that.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



whydibuythis
Novice

Feb 24, 2023, 5:12 PM

Post #3 of 12 (881 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

Yep, luxury off-road SUV for Mazda-beater prices, I definitely know what I signed up for.

This isn't a general repair shop. It's been to a dealership once and a European car mechanic that specializes in Land Rovers twice.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 24, 2023, 5:23 PM

Post #4 of 12 (874 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

Apparently they just don't want to put in the time and effort.

I worked at a European shop and I hated going anywhere near those things.

They are just going to have to do extensive testing starting with a complete compression test.

exhaust pressure test
examine the scan tool sensor data closely and know what to look for
Check for updates to the Engine Control Module
Look for dead spots in the TPS
Problems with the Electronic throttle.
Transmission throttle pressure adjustment



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



whydibuythis
Novice

Feb 24, 2023, 5:39 PM

Post #5 of 12 (856 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

A complete compression test, I understand, but wouldn't a compression issue cause a more uniform problem? ...especially when I hammer the throttle? It performs to spec when I do that.

TPS. Considering I can handle replacing the throttle body myself and the accelerator assembly, would I be best served getting these relatively low cost items handled before I bring it back to the dealership for more extensive testing?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 24, 2023, 5:53 PM

Post #6 of 12 (851 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

Yes, compression can cause numerous strange issues. You can't waste a ton if time looking for driveability issues if you don't make sure it is mechanically sound first.

Throttle body relatively low cost? I don't think so. The OEM is $656 so don't start throwing parts at it. You won't save any money in the long run.

In the future if you want a luxury SUV buy a Lexus RX. I have owned 5 of them all used and all over 100K and have yet to spend a penny in repairs.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Feb 24, 2023, 5:55 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 25, 2023, 1:19 AM

Post #7 of 12 (810 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

whydibuythis > I was wondering that from the get go on this thread.

These need a Rover Dealer WITH a well equipped and trained tech IMO.

So far so good with attempts just one thing to ask is if the dang plug to codes and the light/icon for troubles even works. Turn ignition to run but not running should act as a bulb check, all warnings, suggestions should light up. If the warning bulb doesn't for codes the tech's equipment should have said no info yet or an incomplete?

I avoid these like too or just plain send it on if not obvious issues routine or worse like this nightmare with fine interior appointments (new) still sells IDK why as HT said worst cars known! That for surprises not expected wear items and care maintenance all along,

Tom



whydibuythis
Novice

Feb 25, 2023, 10:42 AM

Post #8 of 12 (793 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

The username is one I started using when I went all in on a brand new Mazda 6 with my teenager minimum wage paycheck back when anything electrical in that car worked so poorly it wouldn't even be able to start a car fire.

It's been to a dealership. It was there for a while. Another, larger dealership sent a tech more versed in the model year to help out also. And thanks, for letting me know they are unreliable, the worst cars ever, even. I also google things.

OBDII port is fine, and yes, all of the lights work. Anyone who buys a used car regardless of brand should check for that. One fuse and you've been successfully had.

It does make sense that you all avoid this vehicle. I get it. Thank you for the list of tests to request and questioning why I would still buy this vehicle in light of what HT said. I don't know what HT stands for, don't much care either, since "Land Rover Most Unreliable" isn't exactly a hot take.

Since you're all mechanics, does anyone have a mechanical guess? A lottery-style, shot-in-the-dark? You get it - if you're wrong you lost two dollars but if you won the world is yours sort of guess?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 25, 2023, 11:03 AM

Post #9 of 12 (784 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In


Quote
Since you're all mechanics, does anyone have a mechanical guess?


Technicians don't work that way. We systematically isolate problems. That's why I rattled off a bunch of tests to look at but that wasn't for you to tell a mechanic what to test. If they are any good they will already know how to approach this and what to test. If you start telling them how to do their job you are just setting yourself up for the whole thing to backfire on you.

HT stands for my user name "Hammer Time" which is displayed on every post.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 25, 2023, 11:09 AM

Post #10 of 12 (773 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

No $ bets the joy is ours if we hit something. HT, BTW = Hammer Time to make it shorter, "T" I sign off is Tom.

GuesscastCrazy Can only be that. Ohm meter to TPS look for the dead spots if any. If none they could be hiding while you check.

Two people easier one hits the throttle, key empower to run position.
You asked for a guess that was HT's early on a list is mine also.

Reason is stuff gets hot, wet, cold constantly the dang things may not take it nor the other 1,000. Time for a pro wouldn't be chargeable time guessing IMO. This spot is free + all volunteer run except for Google watching all of us!

Good luck you ,may stumble upon it. Lousy designs worked once before it's those that lasted. Stuff is computer design hard to impossible to duplicate what time does under all adverse conditions which is why a vehicle is really a feat few do super well the first time,

T



whydibuythis
Novice

Feb 25, 2023, 11:17 AM

Post #11 of 12 (767 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

Experienced people in any job can sometimes extrapolate based on that'd experience if it's broad enough or I'm lucky enough they've either encountered the issue or something of the sort. This seems like an overly circumstantial problem, specific to very few since I can't find anyone who describes their issue like I do. Could be how I communicate it too (which is why I was so long winded in my initial post - trying to avoid ambiguity).

Suppose I'll reply back if I find the issue. Not likely at this point, but maybe it'll be interesting. Thanks everybody.

Definitely going to start with TPS.


(This post was edited by whydibuythis on Feb 25, 2023, 11:20 AM)


Sidom
Veteran / Moderator
Sidom profile image

Feb 25, 2023, 1:05 PM

Post #12 of 12 (751 views)
Re: 2012 Land Rover LR4 has an undiagnosable acceleration issue Sign In

Nothing really jumps out at me about this problem. It is odd that it only does it in 3rd gear and not in other gears, but That doesn't rule out a mechanical problem But it does seem to point to point to another area.
1 thing I would suggest would be to start with the basics. Test the battery check all the grounds, do a voltage drop test over the system Over the years I can't tell you about some of the weirdest problems a bad battery caused That you would never believe could be caused by a battery, I guess one of the weirdest ones was killing an a/c System on a suburban After it would run for about 15 or 20 minutes.

"Slower is faster" It's a phrase you hear most training seminars. Meaning don't look over the basics and jump ahead to the scan data and other stuff. You can wind up wasting a lot of time doing that.... Kinda like that AC system I mentioned earlier. ;)






 
 
 






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