[FantaBlack]

I have a fully stock 2006 Exige with a stubborn P0171 Code: System Too Lean (Bank 1). I've searched the forums and found many useful ideas, but still haven't had any luck.

For some background, here is an ad from the original owner back in 2015 with an extensive list of mods. Prior to being sold, the car was brought back to stock. The second owner, who I picked up the car from, said the P0171 code popped up pretty quickly in his ownership ~300-400 miles in (the car had about 8.2k miles on it).

At this point, with most of the main suspects looked at, and since the code popped up so quickly after the car was brought back to stock, I'm thinking the culprit may be somewhere there. I'm not very familiar with tuning, but could the issue be somewhere with the ECU Chip Tune? If the tune was kept, but the SC, exhaust, etc. were brought back to stock, is it possible the ECU is having trouble compensating and throws a code because of that? If yes, would I have to find a Lotus dealer to reset the ECU?

Work done up to this point:
New MAF Sensor
Replaced both O2 Sensors
Replaced O-Ring on the oil dipstick
Repaired a small crack on the exhaust
Fuel Injectors - Cleaned
Battery Tested
Spark Plugs - Cleaned
Air filter - Cleaned
O2 connectors are in their proper place

Any help is appreciated, thanks!

 

[Catsailr27]

It says new MAF but it doesn't state if cheap ebay aftermarket. If so they've been known to cause issues. It also says battery tested in addition to having it load not voltage tested I would meter your grounds battery->bulkhead>engine.
It says air filter was cleaned? Is it OEM style paper filer and is it full OEM air box?

P0171 code

www.lotustalk.com

 

[PeteB37]

If you figure it out, please post what you did. I've got the same issue with my 2005 Elise. It's even persisted after I got a new ECU.

Gator Motorsport recommended cleaning the throttle body. I did, and no change, but it looks like it's something you haven't tried yet.

 

[exigegus]

So the supercharger was removed but the tuned ecu was kept?
Probably not going to behave well

 

[okc-lotus]

I had a pesky P0171, the battery tested good. When i replaced it, code went away.

 

[Catsailr27]

I have a fully stock 2006 Exige with a stubborn P0171 Code: System Too Lean (Bank 1). I've searched the forums and found many useful ideas, but still haven't had any luck.

For some background, here is an ad from the original owner back in 2015 with an extensive list of mods. Prior to being sold, the car was brought back to stock. The second owner, who I picked up the car from, said the P0171 code popped up pretty quickly in his ownership ~300-400 miles in (the car had about 8.2k miles on it).

At this point, with most of the main suspects looked at, and since the code popped up so quickly after the car was brought back to stock, I'm thinking the culprit may be somewhere there. I'm not very familiar with tuning, but could the issue be somewhere with the ECU Chip Tune? If the tune was kept, but the SC, exhaust, etc. were brought back to stock, is it possible the ECU is having trouble compensating and throws a code because of that? If yes, would I have to find a Lotus dealer to reset the ECU?

Work done up to this point:
New MAF Sensor
Replaced both O2 Sensors
Replaced O-Ring on the oil dipstick
Repaired a small crack on the exhaust
Fuel Injectors - Cleaned
Battery Tested
Spark Plugs - Cleaned
Air filter - Cleaned
O2 connectors are in their proper place

Any help is appreciated, thanks!

What RPM does your second cam kick in at? If 6200 it's OEM tune if 5800 or less it's got a tune and that could potentially cause issues. Some OBD readers will also show calid which can be compared to OEM calid to see if stock tune.

 

[cyow5]

If tuned for a supercharger that isn’t present, it’ll run rich (more fuel than needed because it expects more air than is present). I’d table any tune theories for now and look at other stuff changed around the time the code popped up. Battery issues seem possible, too

 

[FantaBlack]

@Catsailr27 All sensors changed were purchased through the Lotus dealer. I'll ask my mechanic to double check the battery. Same for the air filter. As for the airbox, I think it's OEM, it's definitely not the CF the first owner had. I haven't had a chance to really drive it since it's being worked on, but when I test drove it it came on around 6k lol.

@PeteB37 Sorry you're also going through this! I'll definitely keep you posted.

@exigegus I'm not sure if the tuned ECU was kept, that's what I was hoping to figure out. But like @cyow5 mentioned, it would run rich instead of lean.

I'll have everything mentioned checked, as well as the O2 harnesses again to make sure they aren't swapped. I saw another member recently solve their issue by replacing the spark plugs with the correct temp plugs...I wonder if that could also be a cause.

Hopefully I'll have an update for Monday - thanks for the ideas.

 

[Catsailr27]

Make sure you lather the plug coils with NOOX if you're in there.

 

[exigegus]

If tuned for a supercharger that isn’t present, it’ll run rich (more fuel than needed because it expects more air than is present). I’d table any tune theories for now and look at other stuff changed around the time the code popped up. Battery issues seem possible, too

Perhaps,that is what we would think, but it is going to be wrong one way of the other.

 

[okc-lotus]

Minus the code, how does it idle?

 

[Catsailr27]

Since your car was previously SC and then put back to OEM I would be looking for leaks that happened on reassembly. It could be caused by vacuum lines, exhaust gasket, intake manifold leak, MAF o'ring, so many things. I had a massive vacuum leak 3 broken intake manifold bolts.studs and even a propane test couldn't detect it yet you could hear it plain as day.

I would clean and inspect your O2 sensors and make sure the connectors weren't swapped. Purple lead is post sensor. Check for leaks at exhaust manifold. How about vacuum line and electrical connections at the airbox?

In this link Roundabout has a similar issue p0171 persists

 

[cyow5]

@Catsailr27 All sensors changed were purchased through the Lotus dealer. I'll ask my mechanic to double check the battery. Same for the air filter. As for the airbox, I think it's OEM, it's definitely not the CF the first owner had. I haven't had a chance to really drive it since it's being worked on, but when I test drove it it came on around 6k lol.

@PeteB37 Sorry you're also going through this! I'll definitely keep you posted.

@exigegus I'm not sure if the tuned ECU was kept, that's what I was hoping to figure out. But like @cyow5 mentioned, it would run rich instead of lean.

I'll have everything mentioned checked, as well as the O2 harnesses again to make sure they aren't swapped. I saw another member recently solve their issue by replacing the spark plugs with the correct temp plugs...I wonder if that could also be a cause.

Hopefully I'll have an update for Monday - thanks for the ideas.

I did make the boneheaded mistake of swapping the O2 sensors when I replaced mine, and it also gave me a similar code. Idle was choppy, not sure how yours idles. That's an easy fix though, so hopefully it is that simple.

With that long list of changes in your first post, were those in response to the code or before the code popped up?

 

[FantaBlack]

It idles seemingly with no issues. It sits at about 1K RPM and doesn't jump or hunt for an idle. The little chance I've had to drive it, it never felt like that car was struggling or wanted to die, which makes me think the O2 sensors are fine, but a second check won't hurt.

There was a leak with one of the vacuum lines when a smoke test was conducted which has since been fixed. I'll have the other items checked out.

@cyow5 The list of work/repairs were done in response to the code.

 

[3X163]

It idles seemingly with no issues. It sits at about 1K RPM and doesn't jump or hunt for an idle.

That is a higher idle than a stock NA car should run. So it could be an aftermarket tune (or another leak).

 

[FantaBlack]

That is a higher idle than a stock NA car should run. So it could be an aftermarket tune (or another leak).

Weird, I thought 1K was normal for NA. What should it be at idle?

 

[3X163]

Weird, I thought 1K was normal for NA. What should it be at idle?

I think it states 850 in the owner's manual. A lot of the tunes bump it up to 1k.

 

[cyow5]

It idles seemingly with no issues. It sits at about 1K RPM and doesn't jump or hunt for an idle. The little chance I've had to drive it, it never felt like that car was struggling or wanted to die, which makes me think the O2 sensors are fine, but a second check won't hurt.

There was a leak with one of the vacuum lines when a smoke test was conducted which has since been fixed. I'll have the other items checked out.

@cyow5 The list of work/repairs were done in response to the code.

Mine ran surprisingly well with the swapped sensors, and that was the biggest reason I looked at other places first (like cleaning the MAF, etc). Idle was also smooth at first since the sensors are ignored until they warm up (but that’s only like a minute). Then it would sit fine for a bit, and then I could watch the AFR tank, then it’d stumble, then smooth out for another minute before repeating. With short drives and limiting idling, it could seem fine. Like cat said, visually look at the wiring colors and see if it is right. No sense in not checking.

Hot idle is 850, but if it is cold, it’ll be a touch higher. It’s also easy to misread idle rpm by a tad.

 

[srwhitman]

l've had this issue before - but on an SC car (which is now being totally redone but thats a story for another day). Is the MAF facing down or facing toward the back of the car. My understanding is that its supposed to be the latter- now whether that makes a difference, no idea.

Also, I would change the plugs, not just clean them. Also check the gap. I believe the plugs for the SC cars are different than NA cars.

You said air filter is cleaned - that implies its an oil based filter. Now I usually am for the oil based filters as much as the next guy but you might try going back to paper - that is if you are still running the stock air box.

Another thing - the car is old enough that you may want to replace the coil packs.They are not cheap although its fairly easy to do. I have seen a rusty looking powder in mine before.

It could be that this is more of an annoyance than anything else but it could be real and would be worth getting to the bottom of.

Good luck!

 

[alcantor]

If you want to rule the ECU out, get the Calibration ID and the CVN Calibration Verification Number from your ECU and send me them by PM. If it's a recent calibration, I can tell you if it's OEM or not.