Questions tagged [lean]

A condition where the air fuel ratio is not optimal and the engine is not receiving enough fuel from the fuel system

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25 votes
4 answers
447k views

Symptoms of Lean or Rich carb settings on a motorcycle

I have a 1981 Yamaha XS650. I recently put in K&N stock replacement filter (ie, they are in the airbox and conform to the size of the original), however they may be leading to a leaner mixture ...
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12 votes
3 answers
67k views

What's the meaning of a "lean" vs "rich" air fuel mixture

I'm learning about vacuum leaks on engine intakes and I'm hearing this terminology of lean air fuel mixture. I thought I heard of a rich mixture before too. What's a normal mixture referred to as? A ...
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9 votes
2 answers
7k views

Strange surging and like it's going to stall, hesitant whilst idling

I have been having an issue with my Peugeot 207 (2008 model) 1.6L VTI petrol engine. The cam cover was replaced by the garage but hasn't fixed the problem. I have lost faith in them. I have managed ...
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7 votes
1 answer
4k views

Fuel Trim Readings

I have a 2002 Toyota Corolla (1ZZ-FE engine) and I am trying to understand the fuel trim values I am getting in real driving conditions from my scan tool. I have P0171 code (lean condition) that comes ...
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6 votes
1 answer
232 views

2009 Aprilia RSV1000 - Piggy Back ECU, Should I get one?

I have an Aprilia Tuono, 2009. It seems to run lean after putting an Akrapovic exhaust on it. It makes exhaust popping sounds on deceleration. My boyfriend said I need a power commander on it to ...
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5 votes
2 answers
3k views

Can a permanently stoich or lean running engine ruin a catalytic converter?

It's known a cat can be burned by an engine running too rich for too long, but i wonder what the effects are of constantly running lean. Will the cat just be uneffective because of the lack of CO, or ...
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5 votes
1 answer
128 views

How much leaner can you responsibly run an old engine?

I've got a '76 Triumph TR7 and I was wondering this after I got its carbs tuned after its restoration. As many of you may know, old engines are initially not capable of running as lean as modern ...
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5 votes
2 answers
139 views

Engine lean issues

Vehicle is a 2006 Ford Courier, started having hesitation/loss of power after fill up at a gas station that I'd never been to before. I depend on it for transport so I'm forced to still drive it, ...
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5 votes
2 answers
106 views

Is there a chemical limitation to the mixture an engine can maintain?

I know that the question/title is a bit ambiguous, but I couldn't wrap it in a single sentence, so please let me elaborate. You can change the mixture of an engine for whatever reason. Because of ...
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3 votes
2 answers
7k views

Help on diagnosing positive Long term fuel trim

My vehicle (Ford Fiesta 2014 Petrol) always have a positive long term fuel trim, which means its running lean mostly. The log data that I recorded using torque pro can be downloaded here : Torque Pro ...
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  • 163
2 votes
0 answers
117 views

Emissions per mile of high MPG lean-burn gas-powered cars versus standard gas-powered cars

I am wondering if there have been studies or calculations of the NOx emissions per mile of high MPG lean-burn gas-powered cars versus standard gas-powered cars. Honda made some great lean-burn cars ...
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1 vote
1 answer
80 views

Motorcycle V-Twin CV carbs riding poorly on 1/4-3/4 throttle after carb rebuild

Background: The bike Suzuki Intruder VS1400 model 2000, ran fantastic, but started to stall on idle when I used old fuel in it. What I did: I cleaned the two CV carbs. Didn't replace anything. I found ...
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1 vote
1 answer
120 views

Spark Plug Deposits

So, I pulled the spark plugs today to check to see how the engine is running. After pulling all 6 spark plugs, I've noticed there is a white deposit caked onto the spark plugs. I doubt this is normal ...
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1 vote
0 answers
95 views

No throttle Response at low RPM, Normal performance at normal high RPM

I own a 2007 Hilux, 1kd-ftv 3.0 diesel. Recently my car was occasionally stalling or trying to stall at idle, and having complete engine hesitation from time to time, where the engine would rev when ...
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1 vote
0 answers
46 views

Engine feels like it will stall after Air/Fuel ratio sensor changed?

Got an 04 Acura TSX that's been baffling me for the couple of weeks. Accidentally bought an Upstream Oxygen sensor instead of the downstream so I thought might as well replace it since I have it (keep ...
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1 vote
0 answers
278 views

Help me diagnose my lack of power & lean condition

I have a 2000 Mercedes CLK 320 with the M112 V6 engine at 125 000 kms. The car has rough unsteady idle and is lacking a lot of its power - to illustrate, 0-100 km/h takes exactly 10 seconds, while ...
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  • 11
1 vote
0 answers
490 views

2 Stroke 70CC Scooter Engine

I own a scooter which I blew the engine in Dec 2016. I since replaced the defective parts in it and it now runs great aside of one thing: Bottom end of the throttle is slugish (I'll elaborate) It ...
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0 votes
1 answer
67 views

How can I diagnose if my engine is running lean or rich?

car is running poorly and wondering if it might have something to do with a lean or rich engine. How can I diagnose this so that I know I am in the right direction and it is not one or the other? I’m ...
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0 votes
0 answers
44 views

2014 Ford Mustang 3.7L V6 Bank 2 Lean on startup until engine warms up

I've been having an issue lately that has not always been the case. For reference, my car has an aftermarket air intake (AirRaid) and BBK Long-Tube headers w/ O2 sensor extensions, a catted X-pipe, ...
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0 votes
1 answer
94 views

What do you think of these spark plugs?

Still trying to diagnose an erratic positive fuel trims. Next step will be making sure that the lean condition i have is caused by less fuel delivered or weak spark not a vacuum leak. I pulled spark ...
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0 votes
0 answers
1k views

When second gear is engaged the car doesnt accelerate and engine doesnt rev up? audi a3 1.6 2005

I recently had a gearbox which went through the casing and needed to be refurbished. Had a new clutch replaced along with it. Once i picked the car up i began noticing that when the car goes into 2nd ...
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0 votes
0 answers
797 views

High LTFT (Long Term Fuel Trim) Reading

If someone can help me solving a lean condition issue, I'd appreciated! I bought a 2002 Ford Focus ZTW (Zetec, at 100k miles) a month ago, and I noticed OBD2 always reads LTFT for both bank 1 and 2 ...
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0 votes
2 answers
43 views

How to fix Check engine error P0171 on VW Tiguan?

Took the vehicle for service after the usual 7000km.Parts that were changed during the service are Spark plugs, engine oil type 5W-40, Oil filter, Air cabin filter and Air filter. Two days later l got ...
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