So the issue started when 87 was put in the tank instead of 91/93. A lot of chugging and bad performance. Dumped a bunch of octane booster in. Got to a half tank and have been topping up with 93. I got the "reduced engine performance" error and figured it was the gas.

When good fuel was in it I was still getting the error.

I swapped the air filter (which was dirty).

I discovered the mass air flow sensor was faulty, so I swapped that.

I had a buddy at work clear the codes to reset the cycle, and it gives me the error right away. No more chugging or sputtering when I'm driving, sounds smooth and feels smooth. But it doesn't want to hold idle. At idle it hovers around 400rpm. When I'm driving it'll hop out of limp mode and is great. Come to a start, right back to limp mode.

I'm going to try seafoam in the air intake and see if that doesn't help.

Any other thoughts?

 

Try a computer reset, might force it to re-learn it's performance table faster. But the wrong octane shouldn't really cause bad performance, the engine should adapt to it under normal conditions. It's not good for the engine to run low octane on a long-term basis, but it should tolerate one tank OK.



Disconnect both battery cables (neg first)
Wait ten minutes
Touch battery cable ends together
Wait ten
Connect battery (pos first)
Wait ten
Insert key fob (don't turn on)
Wait ten
Turn car systems on, but not the motor (with foot off brake, press and hold start button for a few seconds)
Wait ten
Start engine, drive around a bit

 

Gotcha. Just so I'm clear on the instructions, when do I reconnect the negative cable?

Seafoam helped a bit. But the idle is still rough. Throws it into limp mode. I'll drive and it'll kick out of limp mode, but a slightly harder acceleration will kick it right back into limp mode. And so it goes.

I'll try resetting my computer over my lunch break.

 

I can read. Darn. You did explain when to connect the negative. Thanks!

 

Alright. Ran through the reset. Still doesn't want to idle well and still kicking in and out of limp mode.

Before I reset the computer I pulled the codes for the check engine light. A couple cylinder misfire codes as well as P0193, which tracks. So, I'm thinking I just need to swap the fuel pressure sensor? I did find an existing thread on that in the LR2 forum so I suppose I'll get that sensor ($20 on amazon) and give it a whirl.

Thoughts?

 

What is the year, model, and mileage of your vehicle?

 

Odd that the reset did not reset the learned pattern.
To be clear, you can either disconnect the positive lead or the negative lead.
I typically disconnect the negative lead and touch it to the positive post. That should “flatten” all capacitance in the vehicle’s systems.
Then reconnect.
Then, without foot on brake, press and release start button.
Then, WAIT for all dings, whirs and chimes to subside. (I assume climate control and audio is off)
Then, depress brake, and touch the start button.
Once revolutions have come to some form of equilibrium, go for a 15 minute drive.
The drive should include varying the revolutions and speed, both city and country road driving. (freeway driving is not the best as other than the acceleration and deceleration moment, revs stay relativity constant )
Then, back to the garage and read the codes.

Other assumptions:
Fuel is correct octane, high quality. (I only use Top Tier fuel)
Filters are clean. (I don’t use oiled filters because…)
MAFs, MAP and PCV are clean.
Cats are in good shape. (if they are old and original, do try Cat Clean, in 1/2 tank. Use up the tank and go through the procedure again). Frankly, I just expect to replace mine at a common interval. But I did begrudgingly try cat clean when throwing codes in the past, while under heavy acceleration and to my surprise, it does work.

Please let us know the outcome.
Cheers

 

It is a 2010, LR2 with approx 167,000 miles on it.

Also, I swapped the fuel rail pressure sensor this weekend, and reset the computer again. Took it for a drive. Still keeps going into limp mode, though, this time I've got no issues with it running hard, or jumpy, or having issues with the idle. I just lose power in limp mode but no hard running.

I haven't had a chance to pull the codes again. I don't have a reader so I end up borrowing one from guys at work. I just drove my old truck to work today because I'm sick of working on the LR2.

I was getting cylinder misfire codes with the fuel rail pressure code, but I was assuming it is because the pressure in the fuel rail was wonky. Think spark plugs are a good place to go next? Maybe the throttle body itself? Pull it and give it a good cleaning?

 

Your symptoms are not typical of the fuel rail pressure sensor failure, but those fail eventually anyway so it didn't hurt to replace it.

Is it specific misfires, or all cylinders?

If specific, try swapping coil packs to see if it follows that. Might as well inspect plugs and change them if in doubt.

Won't hurt to clean TB, that can cause issues.

If you run the wrong oil weight that can mess with the variable valve timing gadget, which uses oil pressure. Assuming N. America 3.2 i6, you should probably use Mobile 1 5W30 (but check your manual, or your oil fill cap). And FFS use a full synthetic, dirty dino oil can also mess up the VVT.

Also possible that you have bad data from crank or cam position sensors? scantool should show that I'd think. Most of those are easy to replace.

Maybe you got some deposits from poor running with the low octane gas? Use a tier one gas (Chevron, Shell, etc you can google a list). Clean or replace the plugs and try an Italian Tuneup (high power, high RPM run to knock buildups loose). Although the car should be able to tolerate an occasional tank of regular gas as long as you're not hauling loads up a hill or something like that. Long term use of regular gas is suspected of causing engine damage on the LR2 and Volvos, so I'd definitely avoid it.

 

Using correct oil and full synthetic. As for the misfire errors it was showing a couple different ones each time I scanned. 2, 4, 5, 6, but never at the same time. And when I'd clear the codes it would give me a different one, but always the fuel rail sensor. Which is why I assumed it might have just been the sensor.

I still need to borrow a reader at work and pull the codes again.

Question: is a faulty water pump potentially part of any of this? Insofar as everything is getting a little hotter than it wants to? I only live 10 minutes from work and don't really go anywhere else so I've been putting off that repair because the engine is only just getting up to temp by the time I pull in.