Really bad FC - 8km/l or 18mpg at best

Hello folks, after selling my first car (a K11 5DR CG10 Auto) in 2008, I told myself I will buy one again if I had some extra cash. 5+ years later, I finally got myself an old Micra K11 (Automatic, 5 door) that had the engine swapped from a CG10 to a CG13 BUT my fuel economy is terrible @ under 8km/l. Admittedly mostly city driving, but it is doing worse than my 2.5L BMW at much lower average speeds!

I have searched extensively and many suggested swapping the O2 sensor, but I'm worried there may be a real systematic issue, such as an incompatible ECU -- I read that the CG13 ECU had less advanced timing at the top end.

I do not have much automotive/mechanical experience. How should I go about troubleshooting? I have no idea if I have the CG10 or CG13 gearbox either.

Any help/advise would be greatly appreciated.
 
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detach8
My consult cable has not arrived yet :(

I've been searching and reading the many many threads on fuel economy, and I've got a rough sense of what I should check.

I disconnected my O2 sensor and drove around for the week with it disconnected. The fuel economy have seemed to have improved a little, so it's starting to point in the right direction; I can't be 100% sure yet until I empty this tank (or get my consult cable).

Another thing I notice is that even with A/C switched on and car warmed up it sometimes idles too low. I read that turning on the A/C should increase idle by around 100rpms. Is this simply a sign of bad idle adjustment or could it also point to a failing coolant temp sensor (to the ECU)? The temp gauge on my dash seems to work fine.

I wish my consult cable would arrive faster.
 
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detach8
I also forgot to mention that my O2 sensor has only one wire. The plug has two pins. I've been searching online and I see 3 and 4 wire replacement parts, but never a one wire replacement.

I understand from some reading that the 3-wire ones have two wires for the heater. It's always hot here in Singapore so I think we don't need the heater and the 3-wire should be equivalent/compatible. I may have to replace the connectors though.

I have a question - will it fit in my manifold? Are all the O2 sensors for CG10 and CG13 the same thread diameter/size?
 
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detach8
Finally managed to get photos into my computer for upload.

Photo 25-8-14 12 04 35 pm Edited.jpg
Photo 25-8-14 12 04 43 pm Edited.jpg



See the connector for O2 sensor -- has only one wire. I found the part number on nissan.epc-data.com (this site is such a gem!) for my original CG10 engine:

Nissan 22690-0U000 or Bosch 0-258-986-501


Also found my temp sensor part:

Nissan 22630-44B10 (direct replacement part 22630-44B20)


Does the CG13 and CG10 share the same O2 sensor, coolant temp sensor, etc?
 
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detach8
Still no sign of my consult cable from eBay :(

BUT I worked on something else today -- decided to calibrate my TPS.

I've been having erratic idle when the engine gets warm. I initially thought... maybe a sticky idle air control valve (IACV) or failing coolant temp sensor, but it seems my TPS calibration may have fixed.

I know there's probably 100s of threads on this, but my limited searching found bits and pieces of scattered information, and there were wrong info going around. So here's sharing what I did: -

Started engine, let it idle and warm up.

Disconnected TPS. Revs rise and then fall. Idle stable at around 750-800 rpms.

Disconnected IACV. Revs rise a little. Reconnected IACV. Revs fall. Left IACV connected. (Conclusion: disconnecting it seems to partially open the IACV?)

Checked waxstat. Could not tell if it was seized with throttle body still bolted on. Might need to do that another day (it was dark out already).

Turned off engine, then started calibrating my TPS.

Here's where my search efforts failed me: -
  1. It took me a while to figure out, but pin #1 is towards the front of the car. The reading should be taken between pins #1 and #2.
  2. Some articles I searched suggested that the reading should be 0.5V (volts) and that is WRONG. We should be measuring resistance (ohms), NOT voltage! The correct reading should be 500 ohms (0.5kohms) with throttle fully closed.
Reconnected TPS. Drove around till engine was properly warmed. No sign of erratic idle.

I also tested my O2 sensor and it read ~0.5V (disconnected from car harness) at idle. I revved the engine a little, and it started to fluctuate between I think 0.2v to 0.6v. At this point it seems to be working fine but the moment I reconnected it I could smell the unmistakable smell of unburnt petrol from the exhaust indicating a rich running engine. I disconnected the O2 sensor, and the smell went away. So it seems I'll be running it disconnected until I get my consult cable.

Looks like the next thing I need to do is to remove the waxstat before I start working on anything else.

Will be away for 2+ weeks and be back late September. My consult cable should arrive by then.
 
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detach8
Looks like my Consult cable arrived just before I leave the country!

Decided to hook it up today to test it.

This is what I see at idle, with my O2 sensor connected. Any clues?

K11_CG13_Idle_Before.JPG


The O2 sensor reading does seem to fluctuate between 0.2-0.7V. If I DISCONNECT my O2 sensor, INJ DUTY seems to increase (both at idle and at 2,000 rpm) so it does show that the O2 sensor is working (somewhat).

INJ DUTY readings:

Idle w/O2 disconnected: ~2%
Idle w/O2 connected: ~1.9%
2K rpm w/o O2 disconnected: ~4.3-4.4%
2K rpm w/O2 connected: ~3.9-4.1%

The CMPS/RPM reading also seems to be a bit lower than the actual tachometer (2,000 rpm on tach = 1,850 rpm on the computer). Seems to be a ~10% error?

Also curios why my IACV is 60% open? Radiator fan is OFF.

Coolant temp sensor is reading 93 deg C, which looks correct, i.e. it's working. Engine is warmed up.

Also now I see the TPS @ 0.30V -- now I know where this voltage reading comes from. You'll need a consult cable to read that. I guess I need to re-adjust my TPS.

But, still no clue why my fuel economy is so bad?

Other info:

If I go into base idle adjust mode my RPMs drop to 600, which I think is probably too low.
 
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Finally got back from sunny California. Managed to buy a static timing light off eBay for under US$40 while there. It's ridiculously cheap for such a decent quality piece of equipment. I can't find anything like this here for under S$100 (approx US$80).

IMG_0518.JPG


Another friend with a K11 (CG10DE) complained that his engine does not seem to make good power after a distributor replacement at a generalist mechanic, so I invited him over.

We had both K11s (both 4 speed automatic) sitting in my carpark last night and started working on our throttle pos. sensor, base idle speed and ignition timing.

TPS adjustment

Friend's TPS was fine (0.46V fully warmed and closed).

Mine was way off @0.30V after an earlier struggle with the multimeter (see post #7 above). It now reads ~0.45V closed. I've seen recommendations in this forum to set it at 0.5V closed being the middle point of the range provided by Nissan (0.45V-0.55V), but I think the upper end of the range is for when the waxstat is cold, so the correct setting is to have it at 0.45V when warm (>80 deg C).

For the record, it reads 4.05V wide open when at 0.45V closed. Both our waxstat seems to be working and the screw holding the mechanism with the green spring has seized, so we did not remove/bypass them.

Base idle adjustment

Fired up the laptop + conzult and put the car into base idle adjustment mode.

Both our base idle settings were too low. In fact, my friend's K11 stalled the moment I put the car into base idle adjust mode.

We got both cars idling at around 780-800 rpms (couldn't get it spot on at 750 rpms but I guess that's OK). It's also interesting to note that the radiator fan puts a considerable drag on the alternator and the engine loses ~30 rpms when it kicks in. We set the base idle with no radiator fan and no A/C running.

Timing adjustment

With the car still in base idle adjust mode, we hooked up the timing light.

Here comes the best part. BOTH our cars had our ign. timing retarded by a fair bit. Both were set at ~10 deg BTDC. We set both our timing slightly advanced -- just a tad after the 15 deg BTDC mark since we get generally good fuel quality here.

Timing.jpg


Note that when advancing timing idle revs also increase, so it is necessary to repeat idle adjustment until you achieve around 750-800 rpms at the desired timing.

Time for a test drive

Right off the line my friend's car (CG10 engine) felt VERY different and also sounded different. It had a more throaty growl when pulling under load and felt much more powerful than it was before.

Mine felt different too (mine is a CG10->CG13 block swapped), but my butt dyno felt it was making less power. It did tend to cruse at lower rpms though. The smell of rich running exhaust fumes also went away, so I think the retarded ignition timing was causing the lambda sensor to read incorrectly making the engine run rich.

Both cars now idle very nicely, irregardless with A/C off or on, fan off or on. We'll continue to monitor for the remaining tank of fuel and report back.
 
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detach8
I'm still waiting for my O2 sensor to ship from somewhere in Lithuania but so far I think there's an approximate 1-2km/l improvement in fuel economy after the idle/timing adjustments. I'm just going through my second tank of gas so I need more mileage to have a good average.

Anyway, is it normal that the power steering hoses route so close to the belts and pulleys? Too close for comfort... looks like it will rub if I go through a bump or something.

IMG_1113-E.jpg


IMG_1114-E.jpg
 
Did you manage to get this problem fixed? I'm having fuel economy issues as well at around 16mpg! I don't even know where to begin diagnosing it. Out of interest how did you calculate the initial mpg for your car? Did you reset the trip meter and calculate how many miles you drove in one increment on the fuel gauge (~1.1gallons)?
 
Hey lads! Im having the same issue on my 2001 K11 1.0 Micra. Taking 13 liters of petrol under 100km. Idle is dropping all the time, and having issues when first start at the morning. For about 1 minute, its impossible to drive away because of the idle dropping.

Detach8 how did you calibrate your TPS? Which one is the TPS sensor?
 

frank

Club Member
Hey lads! Im having the same issue on my 2001 K11 1.0 Micra. Taking 13 liters of petrol under 100km. Idle is dropping all the time, and having issues when first start at the morning. For about 1 minute, its impossible to drive away because of the idle dropping.

Detach8 how did you calibrate your TPS? Which one is the TPS sensor?
yours will be the later coilpack type sandor, so probably a maf issue, try a search on "bosch maf"
 
yours will be the later coilpack type sandor, so probably a maf issue, try a search on "bosch maf"

Yes, this is the latest face lift of the K11. I've already bought an aftermarket MAF. The studdering stopped during driving, and the idle is a bit better, but still my fuel consumption is unacceptably high. Done 420kms for a full tank. The factory MAF sensor is about 280 pounds here in Hungary, which is my monthly wage.
 

frank

Club Member
Yes, this is the latest face lift of the K11. I've already bought an aftermarket MAF. The studdering stopped during driving, and the idle is a bit better, but still my fuel consumption is unacceptably high. Done 420kms for a full tank. The factory MAF sensor is about 280 pounds here in Hungary, which is my monthly wage.


are there any faultcodes ?
 
It had the P0100 fault code which is the MAF sensor. Now the Ecu has been reseted, and since the new MAF sensor plugged in, the code never showed up.
 
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detach8
Hey folks, I'm back after a long period of absence.

Jimmmy, yes what I did was to reset my trip meter every fill up, then just divide distance with qty of fuel to get the fuel economy and it is really bad. You can keep a log, and over several thousand kilometres it should be pretty accurate. I would start with calibrating the distributor as most times the ignition timing will be off if left untouched for many years. Getting the timing right should get you some fuel economy back.

Don't touch the TPS yet unless you have an erratic idle.
 
Hi.
Just to mention that my timing was a little bit off like the both of yours.
And i think that it is related to the chains stretching after 1ooK and more.
 
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detach8
Hey folks, the Micra has been through an engine oil (5W-40), oil filter and spark plug change, and it seems to be running better now. I'm doing closer to 11~12km/l (25~28 mpg) now, and I think I will try advancing the timing a little bit more.

I purchased an O2 sensor off eBay but have yet to install it since the car's mileage has improved. I'll see how it goes.

I've also begun tracking my mileage on Fuelly.com but my car hasn't shown up yet maybe because I only have two fuel-ups. Once I can find it I'll share the link here.
 
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