My DIAHATSU 2010 engine management light stays on.THE DIAGNOTIC TEST shows "FUEL Lean".Car now idling rough and auto fan kicking in as the revs are dropping.Car pulls well but heavy on fuel.

these are the symtoms of a failed egr --which would show the same problems if bypassed or removed --also can cause a no start problem

• Your engine has a rough idle. ...
• Your car has poor performance. ...
• You have increased fuel consumption. ...
• Your car frequently stalls when idling. ...
• You can smell fuel. ...
• Your engine management light stays on. ...
• Your car produces more emissions. ...
• You hear knocking noises coming from the engine

Sounds like the catalytic converter or muffler maybe getting plugged up and the computer is putting the truck in limp home mode. Did you put a scanner on the truck. You might try to remove the 02 sensor ahead of the cat and see if it runs a little better it will not be perfect but should stay running if so do an exhaust check. When the cat or muffler gets plugged it puts back pressure on the engine and won't allow the fuel to be pulled into the engine properly.

I had the same problem on my 2001 Sunfire (same car as the Cavalier-different branding) which I was able to fix successfully.

My symptoms were:
-Traction Control OFF light illuminated
-Cooling fan running even if engine cold and it was freezing outside (I also noticed that when the Traction light illuminated, the fan would then begin)
-Rough idle with black smoke when cold
-Poor fuel economy


I have a code reader which produced codes P0130 and P0171. These are error codes for the upstream oxygen sensor (the one under the hood).

I simply replaced the O2 sensor (it took me 10 minutes). I did not reset the check engine light after the repair as I wanted to see what the car would do on its own. The idle was much smoother with no smoke and the cooling fan stopped running unnecessarily. After 1/2 mile down the road, the Trac light went away and the system functioned normally. I tested this by trying to accelerate quickly up a snowy driveway. I also noticed that the acceleration and shifting (auto tranny) were smoother. I reset the check engine light. All is satisfactory.


What was happening to the car before the repair:

P0130 is usually for a bad O2 sensor and P0171 is the sensor detected that the motor was running too lean (but it actually wasn't-the sensor was essentially giving a false lean signal).
The rough idle, black smoke, and poor economy are due to running too rich. In my case, the sensor told the PCM (the car's computer) that the air/fuel mixture was too lean. In response, the computer said "OK, more gas!" That's why it ran rich. This was evidenced on the old O2 sensor as well...it was completely caked with carbon from an excessively rich mixture. This further destroyed the performance of the O2 sensor.

Really sounds like a vacuum leak. Lean code could still be accurate. Screaming idle usually means air is getting into engine. Ruptured EGR diaphragm would vent air. Brake booster could vent air. A lot of air will show lean mix.

You may have to use different methods to test vacuum. Some use vacuum gauge to test egr and lines which dead end into solenoids. Other tests use water spray or propane gas to draw in and change rpm. You are at a disadvantage if engine does not run.

Crankshaft sensor helps set fuel volume for given rpm. Might not be counting all the rpm's, but would not account for fast idle.

P1131 Lack of HO2S-11 Switch ,Sensor Lean
P1151-Lack of HO2S-21 Switch ,Sensor Lean
PO171- System to Lean (Bank 1)
PO174-Systen to Lean (Bank 2)

Fuel Filter -Plugged
Low Fuel Pressure
Evap System -Leaks
Leaks - in ducting,air filter to throttle
PCV -Leaks
Exhaust System -Leaks
O2 Sensors-worn out

IF THIS IS A V6 ENGINE IT COULD BE ANYTHING, BUT YOU MUST CHECK ALL EMISSIONS EQUIPMENT, VACUUM LINES, CLEAN IDLE AIR CONTROL VALVE AND AND ESPECIALLY TEST AND CLEAN THE EGR VALVE AND TEST MAP SENSOR,AND OTHERS-FUEL PUMP AND FUEL PRESSURE, INJECTORS, ETC..(all fuel related stuff)
NO, NOT AN EASY SOLUTION TO THIS PROBLEM.
IF IT'S A V8 CHECK OUT THIS WEB PAGE.

http://www.thirdgen.org/techboard/tech-general-engine/563375-surging-high-idle-out.html

HAVE VECHICLE SCANNED.AT AUTO ZONE THEY WILL DO IT FREE.SOUND LIKE FAULTY TPS SENSOR,FAULTY EGR VALVE OR O2 SENSOR.MANY THINGS WILL CAUSE ROUGH IDLING LEAN MISFIRE CAUSED BY VACUUM LEAK PVC VALVE OR INTAKE.CLOGGED FUEL FILTER,DIRTY FUEL INJECTORS.GETTING CAR SCANNED WILL SAVE YOU TIME AND MONEY.

Flashing check engine light is missfire, fuel pump probably causing multiple tries to start.Having to build fuel preasure,vac leak on one side of intake probably causing rich/lean condition.Also check back preasure to cat ,Sound like you are moving down right track.Mas air flow would probably set lean code bank1 and lean code bank2

When you have the car in gear there is a load on the engine. If you are for some reason not getting good fuel then its trying to compensate by kicking the idle up. When you are just in park there is no load so its not struggling. Regularly using a fuel system cleaner will help with rough idle, as well as hesitation. Also it might be good to check the fuel pressure regulator.

My service engine soon light stays on. The vihicle shakes as it idles. It act it wants to shut off. What's the problem