Poor economy and juddering

[CMF_redland_doug]

Hi,

I've got a UK 1999 K11. There's a couple of (probably related) issues with the engine. Firstly, it seems to suck fuel. We've had a Micra before, so I know what to expect, and this one does drink. Exhaust looks sooty too. Secondly, it has a juddering/surge-hesitation problem at small throttle openings. Seems to do it whether hot or cold. Basically you get to around 25mph in 3rd, which you can hold with a small amount of throttle and the car seems to surge/fade/surge/fade around twice a second. I checked the ECU codes (nothing - 55). Tried the lambda sensor test (rev engine in test mode 2, look at engine light) and the light winks on and off as expected. The surging/juddering seems to be at about the same sort of frequency - I was wondering if what we're feeling here is the lambda sensor's rich/lean/rich/lean cycling. But why is it so pronounced, and is the over fueling related? Been to a main Nissan dealer who charged £100 for doing bugger-all. Fobbed us off with 'the timing was out' - on an ECU managed car?!?!?!

Lots of talk of throttle bodies on this forum - could it be implicated? I've just got the bits to do it, but am after some opinions before I wade in.

All advice appreciated.

Cheers,

Doug

 

[CMF_frank2]

the solder trick is worth trying doug (if only to rule it out eh)
and a coolant sensor test too (twas covered last week iirc)
the cam/crank sensor is in the dizzy and some slack timing chains (may ?) make it scatter at a certain rpm ?
and you could try different throttle position sensor settings (i think it should be .5v closed)

frank

 

[CMF_redland_doug]

Hi Frank,

I'm being dense - where's the coolant sensor test in these pages?
Also how check the throttle position sensor?

I've got the Haynes, got the multimeter, and the enthusiasm! Just lack the knowledge!

Cheers,

Doug

 

[CMF_frank2]

https://micra.org.uk/cmf/message/51788
https://micra.org.uk/cmf/message/53105
there are a few threads doug (the search button is your friend )

frank

 

[CMF_redland_doug]

Hi,

I did find the time to do the re-solder job (it was actually very easy to do). Unfortunately it made no difference what so ever. :-(

Time to look at other causes.

I know that the lambda sensor sends rich/lean messages to the ECU, but does anyone know how the ECU decides how much fuel to inject? Is it the magnitude of the lambda sensor reading, or it simply thresholded into a binary rich/lean setting? Just wondering if I should be looking at ECU issues, sensor issues, injector issues, cold start thingy not entirely switching off, ... ??? And of course how to diagnose!

Cheers,

Doug

 

[CMF_DECIM8]

Sounds to me like two things.

1 - O2 sensor, controls fuel consumption should be changed every 40,000k

2 - Spark. Either the coil or dizzy or whatever is not sending enough spark etc. Could be leads or anything Check with a multimeter the voltage at each sparkplug. They should be reasonably even.

I would also try add a new power line to alternator to postive battery and battery Negative to body

If the micra runs a Air flow meter this can also be the cause .. I dont think it does but its my daily ive never checked.

At worst also check for leaking injectors.. I dont think this is your issue as you would have excess fuel on start up causing some black smoke. (i.e injector stuck open)

 

[CMF_Peter Felix]

"Sounds to me like two things. O2 sensor, controls fuel consumption should be changed every 40,000k - Spark. Either the coil or dizzy or whatever is not sending enough spark etc. Could be leads or anything Check with a multimeter the voltage at each sparkplug. They should be reasonably even. I would also try add a new power line to alternator to postive battery and battery Negative to body If the micra runs a Air flow meter this can also be the cause .. I dont think it does but its my daily ive never checked. At worst also check for leaking injectors.. I dont think this is your issue as you would have excess fuel on start up causing some black smoke. (i.e injector stuck open)

You say that the 02 sensor which controls the fuel consumption should be changed every 40,000k - where is this 02 sensor located on the engine?

 

[CMF_DECIM8]

Its located from what I remember the dump pipe off the headers or in the headers. you can see a 10cm metal cylinder shape plug on top poking out. This is the o2 sensor.

 

[CMF_Peter Felix]

"Hi, I've got a UK 1999 K11. There's a couple of (probably related) issues with the engine. Firstly, it seems to suck fuel. We've had a Micra before, so I know what to expect, and this one does drink. Exhaust looks sooty too. Secondly, it has a juddering/surge-hesitation problem at small throttle openings. Seems to do it whether hot or cold. Basically you get to around 25mph in 3rd, which you can hold with a small amount of throttle and the car seems to surge/fade/surge/fade around twice a second. I checked the ECU codes (nothing - 55). Tried the lambda sensor test (rev engine in test mode 2, look at engine light) and the light winks on and off as expected. The surging/juddering seems to be at about the same sort of frequency - I was wondering if what we're feeling here is the lambda sensor's rich/lean/rich/lean cycling. But why is it so pronounced, and is the over fueling related? Been to a main Nissan dealer who charged £100 for doing bugger-all. Fobbed us off with 'the timing was out' - on an ECU managed car?!?!?! Lots of talk of throttle bodies on this forum - could it be implicated? I've just got the bits to do it, but am after some opinions before I wade in. All advice appreciated. Doug

Hey Doug, have you tried removing the Lambda Sensor and giving it a good clean with a steel wire brush? I throughly cleaned the Lambda sensor of wife's 1997/98 Nissan March and it improved the mileage quite a bit - even the engine sounds more smooth!!

While cleaning the outside of the sensor, don't forget to gently clean the core of the sensor with a thin flat piece of metal.

regards, Peter

 

[CMF_nz_aj]

MAF
Temperature sensor
Clean throttle
Idle control valve
Fuel pump

If you're getting 15-20mpg, it's going to be at least MAF

 

[CMF_DECIM8]

Oh they do use a MAF... Nice rip it off and use some alcohol spray on that sucker. Clean terminals, bang it back on.