MIL Light glows while running on CNG in Honda city - Team-BHP

rajeevpatel · 13th March 2007, 10:54

We have converted one honda city to run on CNG. the kit fitted is italian Landi renzo. The car is running absolutely fine on CNG as well as petrol. Mileage is good pickup and acceleration is also good. But the problem is when it run on CNG it shows MIL light in dash. When we checked the ECU with scantool it shows error code which suggest mixture is too lean. When we checked the voltages generated by both the o2 sensors it gives 0.975 volt while running on CNG.
Now we want that the MIL light should not glow when running on CNG. What can we do. We have tried to insert resistor of different values on the output of o2 sensor to reduce the output voltage to ecu but it's not working. Is there any way to solve this. Can we make some arrangement such that no change is made when it runs on petrol but when it runs on CNG the reading given to ECU is altered so that it doesn't glow the MIL light.
While driving with scantool connected it was observed that the short term fuel trim remains high while running on CNG and long term fuel trim is low compared to the same when run on petrol. So how to reduce the short term fuel trim which is making th MIL ON on CNG.
Kindly suggest some solution to this problem if anybody has come across

Thanking you.
regards,

Rajeev Patel
p_raj14@hotmail.com
Ankleshwar, Gujarat.

Pankaj401 · 13th March 2007, 16:10

What I know is that running too lean means you are running too hot also. And running too hot is not good for engine.

I think the car needs a retune to burn CNG.

There are guys here who can provide you good direction.

wolfinstein · 13th March 2007, 23:35

If its a new kit, You need a Lamda controller with Stepper Motor, Basically it will Pump Required Gas only and is ECU Based Controller which is set using MUT or OBD..!

Ocassionally, I did get Check Engine Error on my CNG XETA, Which was Lamda Error, Got the System Retuned, Lacking the Lamda as Shrimanker Bedini keep on delaying Lamda Control..!

Ford Rocam · 14th March 2007, 01:13

One should not fiddle around with O2 sensor & ECU, the kit you bought should have support to tackle such kind of problems please get in touch with the installer, putting resistor of different values without knowing its outcome is pure experimenting any wrong connection can result in permanent failure of O2 sensor or your ECU.

Mpower · 14th March 2007, 02:46

Watch the engine temps. As long as its within the safe zone, you are OK. I have seen many OHCs with gas kit showing check engine light.

chetanhanda · 14th March 2007, 04:06

I have not worked or had experience with CNG systems but atleast I know that playing with signal to ECU is not the right way to supress MIL.

Quote:

Originally Posted by rajeevpatel

Now we want that the MIL light should not glow when running on CNG. What can we do. We have tried to insert resistor of different values on the output of o2 sensor to reduce the output voltage to ecu but it's not working. Is there any way to solve this. Can we make some arrangement such that no change is made when it runs on petrol but when it runs on CNG the reading given to ECU is altered so that it doesn't glow the MIL light.

The voltage of the o2 sensor should not be altered, there is a reason why the MIL is coming on, by artificially altering the o2 voltage the problem will not go away.The reading must be brought down by increasing the fuel and not by masking the voltage.You will be simply causing engine knock or engine damage with those lean fuel ratios..

Quote:

Originally Posted by rajeevpatel

While driving with scantool connected it was observed that the short term fuel trim remains high while running on CNG and long term fuel trim is low compared to the same when run on petrol.

How high is it ? Im assuming your STFT has maxed out and the LTFT is more than 20% which is triggering your MIL.

Quote:

Originally Posted by rajeevpatel

So how to reduce the short term fuel trim which is making th MIL ON on CNG ?

The STFT is being increased by the ECU based on your voltage which is screaming out that it is leaning out.
Either reset the ECU and let the ECU add the STFT to the LTFT on its own and see if STFT becomes stable. BUT this is obviously not working as it has already gone above acceptable range of LTFT.

By the way can you check your IPW how long is it on for ? or if your OBD2 software shows IDC , how much IDC % your injectors are on for ? are they maxed out ?
If it was a petrol engine ..u could have increased fuel by increasing injector size, fuel pressure with bigger fuel pump, used a piggback AF controller etc to alter fuel delivery with help of a wideband etc ...similar may be applicable in case of CNG.. ? (maybe similar)
Basically try increasing your fuel/CNG supply..
(Try getting hold of a wideband AFR meter)

Is there a way your CNG system understands/compatible/takes feedback from 02 sensor/obd2 port/ECU ? if NOT then Im confused how the system is designed to work on a existing MPFI engine.. ?

chetanhanda · 14th March 2007, 04:10

Quote:

Originally Posted by Mpower

Watch the engine temps. As long as its within the safe zone, you are OK. I have seen many OHCs with gas kit showing check engine light.

I would panic if my MIL came on..

nitroxx · 14th March 2007, 04:33

your MIL light being on is a clear indication of an adjustment to be made for optimal performance make sure you fix the issue instead of using a workaround only coz you may spend less on cng but if you blow a cylinder or something then theres no point having CNG.

rdkarthik · 14th March 2007, 10:23

I have'nt worked on CNG systems, but this seems like a normal closed-loop behaviour of the sensitive Euro 3 (and some Euro 2) spec ECUs. If ECU detects the afrs do not behave as per ECU predictions and actions, it usually throws a MIL. Nothing to worry about, unless something else is kaput.

You might have to get a CNG kit capable of maintaing at least a stoich mixture, if not closed-loop controller, as wolfenstein said. Most of the LPG/CNG guys tend to go on the leaner side for efficiency, which should'nt be a problem with the typical non-stressed street engine.

GTO · 14th March 2007, 13:31

I guess the NHC does not come with a temp. gauge?

goldie_malhotra · 14th March 2007, 14:09

Quote:

Originally Posted by GTO

I guess the NHC does not come with a temp. gauge?

Nope, it does not - just an indicator for cold/hot.

chetanhanda · 14th March 2007, 22:24

Quote:

Originally Posted by goldie_malhotra

Nope, it does not - just an indicator for cold/hot.

yes..
what "rajeevpatel" needs on his CNG/petrol engine car is a EGT gauge..
the temp indicator gauge is just useless in this case..

13th March 2007, 10:54	#1 (permalink)
rajeevpatel Newbie Join Date: Feb 2007 Location: Ankleshwar Posts: 1	MIL Light glows while running on CNG in Honda city We have converted one honda city to run on CNG. the kit fitted is italian Landi renzo. The car is running absolutely fine on CNG as well as petrol. Mileage is good pickup and acceleration is also good. But the problem is when it run on CNG it shows MIL light in dash. When we checked the ECU with scantool it shows error code which suggest mixture is too lean. When we checked the voltages generated by both the o2 sensors it gives 0.975 volt while running on CNG. Now we want that the MIL light should not glow when running on CNG. What can we do. We have tried to insert resistor of different values on the output of o2 sensor to reduce the output voltage to ecu but it's not working. Is there any way to solve this. Can we make some arrangement such that no change is made when it runs on petrol but when it runs on CNG the reading given to ECU is altered so that it doesn't glow the MIL light. While driving with scantool connected it was observed that the short term fuel trim remains high while running on CNG and long term fuel trim is low compared to the same when run on petrol. So how to reduce the short term fuel trim which is making th MIL ON on CNG. Kindly suggest some solution to this problem if anybody has come across Thanking you. regards, Rajeev Patel p_raj14@hotmail.com Ankleshwar, Gujarat.

13th March 2007, 16:10	#2 (permalink)
Pankaj401 BHPian Join Date: Mar 2006 Location: Phoenix, US Posts: 187	What I know is that running too lean means you are running too hot also. And running too hot is not good for engine. I think the car needs a retune to burn CNG. There are guys here who can provide you good direction. Last edited by Pankaj401 : 13th March 2007 at 16:12.

13th March 2007, 23:35	#3 (permalink)
wolfinstein BHPian Join Date: Feb 2006 Location: New Delhi Posts: 977	If its a new kit, You need a Lamda controller with Stepper Motor, Basically it will Pump Required Gas only and is ECU Based Controller which is set using MUT or OBD..! Ocassionally, I did get Check Engine Error on my CNG XETA, Which was Lamda Error, Got the System Retuned, Lacking the Lamda as Shrimanker Bedini keep on delaying Lamda Control..! __________________ " When was the last time, You did something for the first time "

14th March 2007, 01:13	#4 (permalink)
Ford Rocam Distinguished - BHPian Join Date: Feb 2005 Location: Mumbai-India Posts: 905 View My Garage	One should not fiddle around with O2 sensor & ECU, the kit you bought should have support to tackle such kind of problems please get in touch with the installer, putting resistor of different values without knowing its outcome is pure experimenting any wrong connection can result in permanent failure of O2 sensor or your ECU. __________________ Cheap and reliable wont be fast, cheap and fast wont be reliable, reliable and fast wont be cheap.

14th March 2007, 02:46	#5 (permalink)
Mpower Team-BHP Moderator Join Date: Mar 2005 Location: Chicago/B'lore Posts: 3,637 View My Garage	Watch the engine temps. As long as its within the safe zone, you are OK. I have seen many OHCs with gas kit showing check engine light. __________________ The difference between the men and the boys....................is the speed of their toys.

14th March 2007, 04:33	#8 (permalink)
nitroxx BHPian Join Date: Nov 2004 Location: MUM-DXB-mUM Posts: 761 View My Garage	your MIL light being on is a clear indication of an adjustment to be made for optimal performance make sure you fix the issue instead of using a workaround only coz you may spend less on cng but if you blow a cylinder or something then theres no point having CNG. __________________ "Aerodynamics is for those who cannot manufacture good engines" - Enzo Ferrari

14th March 2007, 10:23	#9 (permalink)
rdkarthik BHPian Join Date: Sep 2005 Location: bangalore Posts: 173	I have'nt worked on CNG systems, but this seems like a normal closed-loop behaviour of the sensitive Euro 3 (and some Euro 2) spec ECUs. If ECU detects the afrs do not behave as per ECU predictions and actions, it usually throws a MIL. Nothing to worry about, unless something else is kaput. You might have to get a CNG kit capable of maintaing at least a stoich mixture, if not closed-loop controller, as wolfenstein said. Most of the LPG/CNG guys tend to go on the leaner side for efficiency, which should'nt be a problem with the typical non-stressed street engine. Last edited by rdkarthik : 14th March 2007 at 10:38.

14th March 2007, 13:31	#10 (permalink)
GTO Super-Admin Join Date: Feb 2004 Location: Bombay Posts: 12,190 View My Garage	I guess the NHC does not come with a temp. gauge? __________________ GTO Self-imposed limits are the only type that exist. Break them....then, make it a habit. Exceed. Please don't PM for support. Use the Contact Form instead. Please read the NEW Team-BHP FAQ section for all your queries.

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