First timer requiring advice - maf and throttle body problem

B

bob49

This is my first post so apologies in advance for any errors in protocol.

Whilst sorting out my wife's damp start problem with her micra (K11 1 litre 1995) my micra (K11 1litre 1996) was not used for about three weeks. When I did start it up it was running quite roughly but appeared to get a little better and I thought that it would clear up in time. It ticks over without a problem but when i put my foot down prior to a long run it "bogged down" and the speed dropped. It cleared up after a very short time but on the return leg it did exactly the same thing. It feels as if it is lacking in power and the accelerator needs to be used more than usual. I am hoping that it is nothing too serious as the car has no value except to me.
I've bought some cleaner to attempt to clean the maf sensor but I am reluctant to start dismantling the maf and throttle body.

Is it safe to just squirt the cleaner down through the "mesh" without removing the maf sensor from the throttle body ?

Assuming it is not the maf sensor where should I start to try and eliminate the cause of this problem ?

Sorry for the lengthy question.
 
h701micra,

The one with the rough running is a 1996 bog standard 1 litre. Sorry if I didn't make this clear in my question.
 
I attempted to remove the air filter today but came to a full stop as I couldn't get it off the throttle housing. According to Haynes it should be a doddle but instead of just lifting off after undoing the jubilee clip it is still securely attached. All I was attempting to do was grease the throttle cable and see if I could get the maf sensor out to clean it.
By the way, h701micra, I neglected to thank you for taking up my cause.
 
MAF sensor is not removable from the throttle body and is a fine whisker wire that is very fragile mounted in a shielding protective Bakelite/rigid plastic tube and must not be physically touched.

The laminar airflow grid mesh will be coated with a black oily sludge on its underside and spraying solvents through it may deluge the mass airflow sensor with said oily sludge residue, creating problems where none may exist.

When was the fuel filter last changed located on the firewall bulkhead? The vehicle is old enough to have considerable fuel tank contents contamination with condensation water and crud foreign bodies sludge! How many miles has it done?

Air filter housing pneumatic airtight seal rubber sleeve tends to meld itself to the throttle body due thousands of hot and cold operating cycles over its 20 year life and is thus difficult to remove first time. The throttle body moving parts, accelerator cable mechanism and cold start auto enrichment device, can be lubricated with a long reach nozzle oil can with the air filter housing in situ.
 
check fault codes:
first easiest quick task is to plug in consult diagnostic checker or use the "paperclip-in-diagnostic-plug" trick to check if the ECU has noticed & stored any fault codes leading to possible causes.

clean oxides off dizzy cap:
heavy white oxide building inside the dizzy cap points will weaken spark, especially during cold starts.

dsc05472-jpg.35803


check spark gap & condition:
spark plug appearance tells you how it's running. check the gap is 1.1mm

remove old fast idle waxstat:
the old waxstat mechanism will seize & stick open. remove the spring loaded cam to allow the throttle to fully close and readjust idle

k750-124-jpg.33770


https://www.micra.org.uk/threads/pollymobiles-rebuild.35251/page-19#post-446256

clean IACV:
make sure the valve is clean and able to operate smoothly.

c725uz-206-jpg.30685


check TPS is working & setup:
check if engine response hesitates during sudden throttle blipping with the TPS plugged & unplugged. faulty if there's no difference. the middle & rear pin of the TPS should be 4.8kOhm when fully closed.

check ECU coolant sensor is working within original spec:
faulty coolant sensor will make it run excessively too rich or lean which doesn't burn well.
h701micra, this sounds similar to ur BMW?

https://www.micra.org.uk/threads/pollymobiles-rebuild.35251/page-119#post-704079

check & replace fuel filter if clogged:
if filter is old original or rusty, prob should replace it.

synchronise dizzy timing with ECU:
dizzy timing will affect how torquey it feels. set idle at 750rpm and check crank pulley timing is 15deg with strobe light.

check manifold O2 sensor responding fast enough:
either with diagnostic checker or paperclip-in-plug trick, check the O2 sensor is responding fast enough (flicker rich-lean twice per sec at 2k rpm)
faulty O2 will make it run rough, too rich and drink fuel.

check for collapsed cat:
damaged cat may make it feel restricted under high load high rpm.
 
bob49 said:
I attempted to remove the air filter today but came to a full stop as I couldn't get it off the throttle housing. According to Haynes it should be a doddle but instead of just lifting off after undoing the jubilee clip it is still securely attached. All I was attempting to do was grease the throttle cable and see if I could get the maf sensor out to clean it.
By the way, h701micra, I neglected to thank you for taking up my cause.
Click to expand...
I'll help if I can

The airbox is that simple to remove, they're just a very snug fit on the throttle body. Twisting and pulling gets them free. I was ready for a sit down after removing mine.

They're the earlier type, non removable maf.
Whilst cleaning the maf will help, chances are on this one it'll need a resolder (if it is at fault)
Its very simple to do even a non solder savvy chap like myself can do it. Remove the square plate and you'll see the channels that'll have dried out ni doubt. Freshen those up and jobs a goodun on the maf front :)
 
Thanks to both for your advice. I will start to go through the points you've raised starting with a new fuel filter and cleaning up the distributor cap. Being of the older generation I can only work when the weather is warm and dry so this might take me a little while to have a go at.
 
h701micra,

Thanks for that. I understand that if I remove the plug to the maf and the car runs well that means the maf is faulty. Is that right ?
 
after removing the air inlet pipe, remember to unbolt the corner of the airbox from this support bracket near the little rubber PCV breather pipe that goes into the airbox.
I once forgot to undo the bolt and snapped that plastic bracket off (aint essential though).

loosen the airbox-TB jubilee clip then just rock/nudge/pull the airbox off the TB, careful not to snap the PCV breather pipe end off the airbox
 
bob49 said:
Thanks to both for your advice. I will start to go through the points you've raised starting with a new fuel filter and cleaning up the distributor cap. Being of the older generation I can only work when the weather is warm and dry so this might take me a little while to have a go at.
Click to expand...


With hesitation and misfire issues, when you change the fuel filter, enhance information feedback via:

1. Catch its fuel contents into a glass jar/bowl to settle out and check for water content.

2. Manually cut open (hacksaw) the drained old filter to check its internal condition and contents.

With the above multiple choice complex remedies that you been given, may I suggest you work through them one at a time and then drive the vehicle for a few days to check for changes? Improvements or new faults inadvertently created; at least you will then know where to look.

NB: If the Orange check engine light illuminates during ignition on, and goes out when the engine runs, it is very unlikely that any useful OBD1 fault codes will be stored and this distraction can be eliminated.

Between us all let’s see if we can keep this old car going for another year with absolutely minimum work effort, time and cost by doing only the right work in the right order!

Happy hunting, good luck.
 
plmval,

Too late I'm afraid. I changed the air filter and fuel filter yesterday. Judging by the way the fuel poured out of the filter it not seem to be too blocked. I also cleaned up the inside of the distributor cap.

I took the car for a run and although it did not "bog down" it clearly lacks the power that my wife's motor has. The car was not used for a good time over Christmas as I was waiting for a dry day to repair a blowing exhast. When I did this I found the car needed a new exhaust middle section so I ended up paying to have that fixed. Then my wife's motor started with problems starting after overnight damp and my car was not used for a good three weeks. When I came to use it again it was really rough and underpowered compared to my wife's. I suppose that using it on a day to day basis I did not notice the deterioration in performance.
Anyway today I am going to attempt to get the spark plugs changed and try again to remove the air filter housing. I've found it virtually impossible to do anything with this on.

pollyp & h701micra,

Thanks for the further advice. The airfilter housing is that tight I can rock the car. I'm still pretty strong so I frightened I'm going to damage something trying to get it off. I know I've followed the instructions to remove all the air filter housing fitments. Is it possible to remove the mesh on the throttle body housing with it in place ? The mesh looks as if it is secured by a sort of circlip.
 
The circlip is pretty weak compared to what you expect. It will come off, the large mesh cones free if pulled straight up. There's a spring washer under that so be wary, but it's all simple

Don't worry about breaking it. I was twisting and pulling for quite a while. They are tough
 
Lack of Power.
In the absence of hesitation /misfiring, kangarooing and idle issues it is unlikely that the throttle body mass airflow sensor is at fault and alternatives could be considered first. Lack of power is more likely to relate to engine condition compression, fuel pressure injection issues, timing, and a failing HT coil among many others.

Laminar airflow mesh grid is secured by a dedicated spring clip designed to be maintenance free for the life of the throttle body and inaccessible to all but competent persons equipped with special tools.

Look very closely at the two ends of the spring clip and they can be seen to be tapered. It’s possible to wedge small terminal screwdrivers between one end of the clip and the throttle body housing to prise the clip out its recess slot. Be careful not to damage the Laminar airflow grid as it is essential for accurate mass air flow measurement.

Reference; https://en.wikipedia.org/wiki/Laminar_flow

NB: the MAF hot wire is self-cleaning every start stop cycle by the electronic controls that heat the hotwire to high-temperature to burn off any contamination. Sometimes using magnifying glasses it is possible to identify whiskers of air filter paper debris around the hotwire within the Bakelite protective tube that may slightly affect accurate airflow measurement.

Do not directly spray any solvent on the very fragile hotwire (especially when hot and working) that will leave a residue on it. Iso-Propyl Alcohol (IPA) is a suitable low risk solvent.
Reference; http://uk.rs-online.com/web/p/precision-cleaners-degreasers/0132508
Happy hunting, good luck
 
plmval and h701micra,

Thank you both for taking the time and trouble to offer up your thoughts and advice.

Today has seen me change the spark plugs for some "newish" ones. These were actually returned to me when I had the car serviced at a garage.
I finally managed to get the air filter housing off. I think the effort I put in the other day had paid off because it came of fairly easily. I have to say though that I would not have persevered if it had not been for the encouragement I received from all the earlier responses. I did not remove the accelerator cable but oiled and greased both ends as well as the accelerator spring.
I took it out for a long thrash and the power has perked up, even though it still does not seem as responsive as my wife's car which has a few thousand fewer miles on the clock. Tickover is perfect. The exhaust sounds as if it it is blowing a little but I can find no sign of where that might be.
I'm going to leave it for a few days but will lob in a bottle of "cataclean" as this worked wonders on my wife's car when it played up beacuse of the short runs she does.

Thanks again.
 
Is the power throttle dependant? Ie seems fine if pressed slowly and gradually but seems sluggish uf pressed quickly?
 
h701micra,

Difficult to describe. By comparison my wife's motor is far more responsive. With that you can blip the accelerator and you can tell it's firing properly. Doing the same thing with mine the engine speed picks up but more often than not does not die back quickly. The power has picked up but it still doesn't feel right. I'm "old school" so I took it onto the M5 near Bromsgrove yesterday and gave it a blast. Speed in fifth, foot to the floor, going up a steep gradient topped out at an indicated 70. In fifth I was not gaining any speed. My wife's motor flies up the same gradient in fifth. The car feels almost like a diesel. I am wondering if I have got the possible causes wrong. Could it be something as simple as a bunged up cat ? The car smelled of burning after coming back from a trip. I know the difference between a normal "hot engine" smell and burning. When I grew up my first transport was a BSA 250cc Gold Star (not the classic!). I used to do as much of my own work as possible but these days I can't take the cold and damp. Sorry to ramble on but I wanted to let you know I can tell when something is not quite right. The car was used daily on a long run when I was working but for the last few years it has been used on short runs. It is one of these that will not start if it is only started up for a few seconds. When I shift it to allow my wife's car out I have to sit with it running otherwise it won't start next time. I know the car inside out and until the last few years I used to check oil, water, horn, lights & tyres religiously every weekend. Neither of the micras has used a drop of oil outside of routine changes. I have let the servicing schedules lapse as they have cost a lot to get through Mots so my problem lies, at least in part, in that.
 
They run forever so to speak without much maintenance. Missing a service shouldn't be cause for much concern.

Reason I asked if it was throttle dependant was because ny BMW has recently been a pain in the neck with it and has a blocked cat. If the throttle was pressed to hard/fast it would die out not rev.
From that I'd say your cat was ok but it cant hurt to look
Did unplugging that MAF sensor help? Other than a little higher fuel consumption, if it helps you might as well leave it unplugged. You could clean it with electrical degreaser to help it along.

Another few things to check
- Distributor (the gubbins can give up the ghost) not giving a great spark
- Fuel pump - if it's not throwing enough fuel in it'll struggle to make the desired power. Running leaner could explain the heat?

I can't imagine it being much else but then I've not long been awake
 
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Lack of power?

  1. Insufficient spark intensity possibly due to reduced voltage power supply to distributor HT coil or a failing HT coil? Common problem of corroded fuse box wire terminations, fuse holders and fuses high resistance connections producing voltage drop.
  2. Compression?
Adjustable gap spark intensity tester: http://www.pedparts.co.uk/product/950/spark-ignition-tester

Timing?

  1. Retarded valve, ignition timing due to a worn stretched cam chain?
  2. Exhaust leak introducing excess oxygen creating O2 sensor and consequent fuel mixture error?
  3. Low fuel pressure, or dirty injectors and poor spray pattern?
Overheating?

1. Tardy old thermostat not fully opening?

2. Partly restricted radiator flow, and fan not cutting in?

3. Over advanced timing?

Unresponsive throttle

  1. Sticking throttle plate due to carbon sludge build up in throttle body? Sticking throttle cable?
  2. Throttle position sensor may have been previously erroneously moved and need recalibrating.
Inspecting, testing and verifying above together with other members suggestions is going to take commitment of time dedication and perseverance to an old car, perhaps above and beyond the call of duty, when its remaining economic useful life is dependent upon the next annual “kiss the MOT testers donkey” exercise to fund his budget? bob49 Quote " I have let the servicing schedules lapse as they have cost a lot to get through Mots so my problem lies, at least in part, in that" ?

Happy hunting good luck.
 
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h701micra,

Thanks for posting. I've not yet unplugged the MAF sensor as I had those problems getting the air filter housing off. I've got Cataclean on order so that's my next job. It worked brilliantly on my wife's car. The MAF sensor will be next if that doesn't work. When I do that I will fully lubricate the accelerator cable and adjust it. If the car runs well with the disconnected MAF sensor I will give it a clean through the mesh with Halford's electrical contact cleaner which I understand is perfect for the job. In doing so I'm hoping the this will clean the throttle body and its "butterfly". The distributor and fuel pump are last resort jobs for me. There was a time when I did all of this 'cause I had no choice. I've missed the last two minor services on this car. My mileage is less that 2000 a year and I've always used fully synthetic oil and this is showing no sign of contamination.
 
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plmval,

Thanks for posting.

The lack of power seems to be improving albeit very slowly. I've given the car two or three good hard runs and although things are better they are still not "right". That link you posted looks interesting and I might invest in one of those at a later date.

As regards timing I wouldn't know where to start. I don't think the timing chain will have stretched as I've always used top quality oils which until recently were changed every year.

The car was not overheating as such. It was a smell of burning. This only happened at both ends of the same journey. The temp gauge is showing normal readings and the fan cuts in correctly. If memory serves me well my wife's car was the same with a blocked cat but we'll see if mines the same once I've slung some Cataclean into it.

The throttle I hope will be sorted out by fully lubricating the cable and spraying cleaner down the throttle body.

I take your point about whether or not it may be worth the effort with an old car. The cost of the MOTs on both cars has been mainly for welding rather than anything else. My wife loves her motor and it got through the last test without anything needing to be done. My car needed a lot of welding so I made a conscious decision to spend the cash which was far more than the value of the car. I can easily afford to go out and buy a new car without denting my savings. I am of a generation that believes in fixing things rather than throwing them away and am cursed with a combination of a stubborn streak a mile wide and an obsessive personality which means once I start something I cannot let go.
 
Agent_Sm1th,

Thanks for your post. I did check each wheel for excess heat after a long run but there was no sign of that. However there was a noticeable but intermittent wheel squeak when I went out in it yesterday. This is one for me to check. I am always reluctant to jack up the car because of any corrosion in the sills.
 
bob49 said:
Agent_Sm1th,

Thanks for your post. I did check each wheel for excess heat after a long run but there was no sign of that. However there was a noticeable but intermittent wheel squeak when I went out in it yesterday. This is one for me to check. I am always reluctant to jack up the car because of any corrosion in the sills.
Click to expand...
Use a trolley jack under the rear axle beam and under the front suspension arms rear bush mounts.
 
Update.

Cataclean (in a nearly empty tank of fuel) and Redex fuel injector cleaner added later. Fuel tank filled. Rear section of exhaust replaced. Brand new spark plugs fitted. Sprayed all the external moveable parts of the throttle body with WD40. Sprayed the inside with electrical contact spray to clean the MAF. I couldn't work out how to get the accelerator cable out to grease it. The motor seems to be very close to old performance levels which leads me to conclude that the petrol in the tank had gone "off" and caused the woeful performance. The only thing now is the exhaust note !!!! I am assured that the exhaust is designed these days with a small hole at the back to allow condensation to escape. This leads to a noisier exhaust note which does not impress me as I like my car quiet. Still its a small price to pay. I shall be giving it a good blast later so will be able to check everything is OK.

Thanks again for all the suggestions as to what I might check and how to resolve potential problems. I've learned a lot. The car has been that reliable over the years I've had very little to sort out.
 
Hi, need help too on the same issue. If the rev reaches 2k plus, sometimes it does not returnbto normal idle so stays at around 2k. But if you turn off and start again, idle is normal. Have now plugs, changed fuel filter, air filter, change oil and filter, spayed MAF with CRC MAF cleaner and the latest I did was spray and clean the AICV with throttle cleaner. But still have the problem, I am I missing something else? Thanks
 
monallyza,

Sorry !!!

You've seen the extent of my knowledge above. The engine speed on mine now drops back but not instantly and I've compared it with my wife's motor and it is the same so I think it is working OK. I'm fairly sure my issues were caused by petrol going off in the tank.Good luck sorting yours out.

bob49
 
Thanks. By the way, what type of gasket is there when removing the TB? Can I reuse it or I need to have a replacement before I remove the TB?
 
monallyza, if you follow pollyp's advice above and remove the mechanical/spring control of the waxstat ( so easy, just two small Philips screws, but just watch the spring for tension as it can "ping" off abruptly ) I think you will find this resolves your issue
 
monallyza,

I didn't remove the throttle body so I'm afraid that I can't answer your question although I do understand that it can be reused if careful.

bob49
 
Hi yorkiesteve, as I read pollyp's post. My undertanding is totally remove the spring which means that the waxtat do not function anymore. Is that right?
 
That's right monallyza, when you remove the spring and cam it effectively eliminates the mechanical side of the cold star system. I've done this to both my Micra's and it stopped the crazy high revving when cold, a big improvement.
 
Also, re soldering the throttle body can be done in place, but I removed mine to do it ( but in my case it didn't make any difference to how the car ran ) my issue was high revving when cold, and disabling the wax stat cured the problem
 
Hi yorkiesteve, thanks for the info. For my case it's reving high when hot. Off the engine and re start again brings the rev to normal. But then again revs high as you travel further. Anyway, worth to try this weekend.

Sent from my GT-I9195 using Tapatalk
 

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