Oxygen sensor related problem

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frogcow
Helpful MS/Extra'er
Posts: 56
Joined: Sun Sep 04, 2005 9:56 pm

Oxygen sensor related problem

Post by frogcow »

We have a MS v2.2, The engine is a daihatsu cb sohc turbo

We are having a problem with the oxy sensor. The car idles fine and warms up nicely but after the pedal is depressed past 3300rpm the oxygen gamma reading drops from 98 to 67 and just sits there, this causes the car to shudder through gears (lean I think). Sometimes if I pull over and idle for a few minutes it pops back up to 98 and drives fine for a while until it drops down again.

I have looked at the Ve table in the tuning dropdown and the 02 volts guage on the left hand side rarely has a reading. Also in the tuning dropdown in the realtime display, the first bar that shows the 02 levels rarely shows anything. I have changed the 02 sensor and it didn't change it. I will check fuel pressure but I was hoping this was a easy fix?

Any ideas?
Last edited by frogcow on Tue Apr 18, 2006 12:09 am, edited 1 time in total.
Jim
Experienced MS/Extra'er
Posts: 219
Joined: Sun Aug 28, 2005 9:50 am
Location: Atlanta , Georgia

Post by Jim »

Are you running a Narrow Band or Wide Band O2 Sensor ?

How close is the O2 to the Turbo , could it be overheated ?

Are you running under Boost when this happens ? How much ?

Are you depending on the O2 to tune or fix your VE Table ?

How did you arrive at the VE Table you now have ?

If your Advance Table is wacky , it could cause similar symptoms .

Is the engine pumping out Black Smoke ? if it is , the engine is way too rich ,
If it's not then the engine is way too lean or the ignition timing is wacked ,
If I have to tell you this , are you sure you should be attempting this
without help ?
ESPECIALLY on a TURBO ENGINE !!!!
pastaracing
MS/Extra Newbie
Posts: 3
Joined: Tue Apr 04, 2006 1:03 am
Location: Sweden

Post by pastaracing »

I had the same type of problem with my Charade if i understand your problem.
I attach a O2 sensor with a led-display in the downpipe just to see the lambda-value when I try to run on etanol. I recoginze that after 10 minutes of running when the engine was warm the display go from lambda 1 to leanest possible when i pressed the trottle.
It didn't go back to normal until i idle the engine for a couple of minutes.

My engine was a cb-81 with a carburettor/turbo configuration.

I had ideas about oil from turbo or from poor pistonrings or something, eg oil on the sensor.
Just writing this so you know that you not alone.....
Jim
Experienced MS/Extra'er
Posts: 219
Joined: Sun Aug 28, 2005 9:50 am
Location: Atlanta , Georgia

Post by Jim »

To pastaracing ,

You guys MUST specify if you are running Wide Band or Narrow Band !!!

Since you are switching to Ethanol and losing your O2 Sensor you are
probably running a Narrow Band Sensor that is not heated (one wire)
and the Sensor is getting too cold to work .

Unheated Narrow Band O2 Sensors depend on exhaust heat to keep the
element over 700 degrees , below this they just stop working .

Even with a Wide Band Sensor , which all have heaters , if you run
rich enough with Alky the heater can not produce enough heat to achieve
working temperature and the Sensor will act strange or stop working .

Alky , contains Oxygen and therefore will operate over a wider range
of mixtures , you could easily be running way too rich and not realize it .

If you don't have heavy blue smoke out the tailpipe then oil fouling
is probably not a problem .
pastaracing
MS/Extra Newbie
Posts: 3
Joined: Tue Apr 04, 2006 1:03 am
Location: Sweden

Post by pastaracing »

To Jim,
I'm sorry that i didn't wrote narrowband but I was just tying to add some possible reasons that the oxysensor died. I had the same problem both on ethanol and gasoline. The sensor was mounted 30cm from the turbo so I think it was heat enough. And, Yes, I had blue smoke from exhaust when boosting, my car has 140000km on the speedometer, and this is a Charade-problem I think.

Otherwise, keep up the work!!
1litre 3-cylinder, turbo-boost machine rocks !!!
Jim
Experienced MS/Extra'er
Posts: 219
Joined: Sun Aug 28, 2005 9:50 am
Location: Atlanta , Georgia

Post by Jim »

Blue Smoke is really bad !!!

Oil , whether it comes from the Turbo bearing
or from the rings will make your engine Detonate or Knock ,
just like a diesel engine ,
Gasoline engines will not live long (seconds) with Detonation while under boost .

Probably the only reason your engine still runs is because of the Alcohol .

You must get this fixed before you turn your engine into a boat anchor .
frogcow
Helpful MS/Extra'er
Posts: 56
Joined: Sun Sep 04, 2005 9:56 pm

Post by frogcow »

Hi Jim
Are you running a Narrow Band or Wide Band O2 Sensor ?
I have tried both the one wire and four wire narrowband sensors, the latter is the one that I am currently using.
How close is the O2 to the Turbo , could it be overheated ?
it sits half way down the downpipe, where they usually go.
Are you running under Boost when this happens ? How much ?
Yes, up to 15psi
Are you depending on the O2 to tune or fix your VE Table ?
I use open loop 95% of the time, the few times I have used close loop the engine consumes fuel quicker. the newly installed 4 wire 02 sensor read .90 volts when it is working and 0.02 when it is not.
How did you arrive at the VE Table you now have ?
We used the ve table generator, estimated hp and tq
If your Advance Table is wacky , it could cause similar symptoms .
The timing is about 2cm advanced, where is the advance table?
Is the engine pumping out Black Smoke ? if it is , the engine is way too rich ,
No, white fuel smoke (leaning out) when changing gears only under load

If it's not then the engine is way too lean or the ignition timing is wacked ,
If I have to tell you this , are you sure you should be attempting this
without help ?
ESPECIALLY on a TURBO ENGINE !!!![/quote]

Here are my constants, enrichments, and part of my ve table, perhaps you can see something I can't...from megatune.


Fuelling
61 CId 993CC
3 cylinders
27 Ib injectors
12.7 fuel ratio

Enrichments page
2.0 150 1.563
10 150 0.1
1.2 140 1.5
135 150
40 145 30
150 140
135 Fuel Bins
Narrowband 130 5.0
0.451 120 10.0
145 100 22.0
1 25.5
1
2
600

Bottom part of ve table

200
150
100
90
75 75 80 85
60 70 74 78
45 55 59 72
30 50 54 66
700 1200 2100


If there is anything else you need to know or if there is an easier way to display my tables please let me know.
Thankyou in advance David
Jim
Experienced MS/Extra'er
Posts: 219
Joined: Sun Aug 28, 2005 9:50 am
Location: Atlanta , Georgia

Post by Jim »

Narrow Band 02 Sensors WILL NOT work with alcohol .

You must have a Wide Band Sensor .

Narrow Band Sensors are either "ON" or "OFF" , they switch on or off
at exactly 14.7 to 1 AFR , you have to run your engine at at least
13.5 to 1 (gasoline) while under boost , alcohol or not ,
and with a Narrow Band Sensor
you are completely in the dark as to what your AFR is .
If it ever indicates less than 14.7 while under boost your engine is toast .

You are going to destroy your engine the way it is setup now .

There is no such thing as "Lean White Smoke" .
You are burning oil , this is death to a Turbo engine .

Where is the Advance Table ?
I hope you have a backup car to get to work .

You really need to get some hands-on help ,
you just can't run boost and not know these things .

The MS website has tons of great info for setting up your box .

There are hundreds of websites with Turbo information .
Do a Google search .

What you are asking for is a complete education on engines ,
it's way too much for me to do .

Good Luck !

...................Jim
'95 GM 4.3 Vortec V-6
Single Plane Intake w/ported GM Throttle Body
Ported Heads , stock roller cam retarded 8 degrees
MS-II 2.6 , V-3 board , MT 3.0
EDIS ignition , Innovate WB 02
250hp , 28mpg @60mph in a 2 ton wagon
frogcow
Helpful MS/Extra'er
Posts: 56
Joined: Sun Sep 04, 2005 9:56 pm

Post by frogcow »

Narrow Band 02 Sensors WILL NOT work with alcohol .
Jim its running on Bp Ultimate and its the Megasquirt 1 v2.2 hence why I couldn't find any advance table.

I understand the need for a wideband 02 sensor at least to do an initial tune. Could you please explain further how a narrowband 02 sensor works. Why does my voltage reading sometimes read zero? and other times read 0.90? Is this the difference between on and off. If I can find out this maybe I can find out what is causing the engine to lean out.

I have rebuilt several engines from bottom up and I have done the whole conversion myself but I try to act simple so I get more ideas thrown around no matter how simple they are, anything is better than nothing.

My engineering pal guru said the afr needs to be 12.7 so that the computer can recognise boost and a narrowband sensors range is around 13.5 to 15 and thus wont register anyhting outside thus a wideband would be appropriate.

So is there a way to stop the leaning out without forking out A$600 for a wideband 02 sensor.

thanks David
Jim
Experienced MS/Extra'er
Posts: 219
Joined: Sun Aug 28, 2005 9:50 am
Location: Atlanta , Georgia

Post by Jim »

WB 02 Sensors have gotten much cheaper .

Around $200.oo for an Innovate LC-1 Controller and Bosh 02 Sensor .

I put off putting MS in my car for almost a month just so I would have
the WB Sensor ready and working .
I would not have even considered Fuel Injection without one .

This is where I got mine , http://www.diyautotune.com/
I like the way he does business .

Check out the picture ->

...................Jim
'95 GM 4.3 Vortec V-6
Single Plane Intake w/ported GM Throttle Body
Ported Heads , stock roller cam retarded 8 degrees
MS-II 2.6 , V-3 board , MT 3.0
EDIS ignition , Innovate WB 02
250hp , 28mpg @60mph in a 2 ton wagon
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