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Discussion Starter #1 (Edited)
Hi, i have a 2007 Lotus Exige S (it is a federal version, imported to Norway where i live)

A few weeks ago, on the german autobahn, on my way home from Nûrburgring, it started to misbehave betveen 2000-4500rpm, it is just like it holds back on power, and if i try to hold the trottle pedal steady, it is "behaving like a kangaroo" When checking the fault codes, it trows "P0171 powertrain too lean bank 1, and P0172 powertrain to rich bank 1"

I have checked for air leaks, with spraying starting gas around the engine, with no result. I have changed spark plugs (the old one looked fine) both O2 sensors, MAF sensor,and MAP sensor, but still the same.
We have also confirmed that fuel delivery/preassure is normal, and the same with exhaust preassure.

The car is ideling fine around 1000rpm, and runs great over 4500rpm. There is also no issues if i am reving the car at a stand still, it goes thru the whole rev range 1000-8400 without any hesitation.

Anyone else that have had this issue, or know what could cause it?

My local mechanic do not get all the information from the car on his diagnostics, and it is a 1000km drive to my nearest Lotus dealer in Copenhagen Denmark.
 

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I’ve similar fault codes upon purchasing the car 2 years ago. Took me 4 months to sort it out from swapping out ECU, throttle body, pedal potential meter till I finally changed out the engine wiring harness and the car behaves back to normal. Do try with your nearby lotus dealer/Mechanic on isolating the fault codes. My 5 cents worth advice. Good luck Pal.


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Discussion Starter #3
Thanks, the issue as described is that my local mechanic (who is very skilled and works on all kind of super/hypercars) do not get much information when using the computer to check for fault codes, and i need to go to another contry to get to a lotus dealer.
 

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Just a few thoughts

You said you checked fuel pressure, but under what conditions? Was the car under load? Have you looked at the fuel filter? Do you know what clutch slip feels like? Do you have an OBD2 reader that can provide real time data? That and a buddy to drive the car while you look at the data would be telling.
 

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Are there any pending codes? I had an intermittent fuel injector issue that didn't always throw a code, sometimes it would give a pending code and sometimes nothing but you could hear the miss when it happened. Check all the grounds on the engine harness and check the wires going to all the injectors and coils. These wires are all covered and can sometimes be damaged when replacing those covers. If you can easily duplicate the issue you should be able to find it or at least know when it's fixed.
 

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Discussion Starter #7
Just a few thoughts

You said you checked fuel pressure, but under what conditions? Was the car under load? Have you looked at the fuel filter? Do you know what clutch slip feels like? Do you have an OBD2 reader that can provide real time data? That and a buddy to drive the car while you look at the data would be telling.
Me and my mechanic hooked up a preassure gauge into the fuel line, and took the car for a drive, while checking it, and according to the mechanic it is all good, it also deliveres the right amount of fuel that is should. He also have had his diagnostic tool with him in the car, while we where out driving, but the only codes we get is "P0171 powertrain too lean bank 1, and P0172 powertrain to rich bank 1"

When i accelerate between 2000-4500rpm, it feels like the car is drowning in fuel, but if i let off, just slightly it comes bac to life, and when it passes 4500rpm it is fine. It is the same int the 2000-4500rpm range, either i am doing 30kp/h in 2. gear or 130kp/h in 6. gear.
 

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Discussion Starter #8
Are there any pending codes? I had an intermittent fuel injector issue that didn't always throw a code, sometimes it would give a pending code and sometimes nothing but you could hear the miss when it happened. Check all the grounds on the engine harness and check the wires going to all the injectors and coils. These wires are all covered and can sometimes be damaged when replacing those covers. If you can easily duplicate the issue you should be able to find it or at least know when it's fixed.
"P0171 powertrain too lean bank 1, and P0172 powertrain to rich bank 1" is the only codes it is throwing, and we have looked over all we can of hoses and wires around the engine. But this is a "ststic" fault that is only between 2000-4500rpm and as long as the car is under load.
 

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I had the same issue on my 07 Exige. The issue was the airflow was reading incorrectly at high loads caused by a dirty mass air flow sensor. After cleaning it, no issue.

Hopefully your issue was as easy as mine.
 

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I have experienced this issue. This particular car had the 1st and 2nd O2 sensors plugs swapped. It would cause more issues the more it was driven.
 

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Try a different ECU and change your engine harness, I have seen this issue before caused by a faulty harness.
 

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I had the same issue on my 07 Exige. The issue was the airflow was reading incorrectly at high loads caused by a dirty mass air flow sensor. After cleaning it, no issue.

Hopefully your issue was as easy as mine.
This was my thought as well. Either dirty or faulty otherwise
 

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Discussion Starter #15
I had the same issue on my 07 Exige. The issue was the airflow was reading incorrectly at high loads caused by a dirty mass air flow sensor. After cleaning it, no issue.

Hopefully your issue was as easy as mine.

As described in my first post, the MAF is swapped for a brand new one.
 

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Discussion Starter #16
I have experienced this issue. This particular car had the 1st and 2nd O2 sensors plugs swapped. It would cause more issues the more it was driven.
Both sensors are swapped for new ones, and with the plugs from the harness placed where they belong, the cables on the sensors are not long enough to reach if they where swapped.
 

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Discussion Starter #17
Try a different ECU and change your engine harness, I have seen this issue before caused by a faulty harness.
It is not easy to get another ECU to test, as there are only 3 cars like this in Norway, and it would be quite expensive to buy a new ECU and harness just to try this out. I have already swapped parts for about $800 without a result.
 
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