Causes Of Lean Running

[roccorich 16]

The plugs on the car were very white when I changed them.

 

I found the vacume advance was leaking so that is bunged up now but its still running lean as the new plugs are white now.

 

I have looked for other air leaks but not found any. Cant hear any leaks and sprayed easy start everywhere but found nothing.

 

Put a fuel pressure guage on and it was showing 30psi about 2.8 bar. So that seems ok.

 

Its a 1.9 D6B engine in a CTI.

 

The AFM and ECU are 1.9 items and the injectors are yellow.

 

Is there anything else people would suggest I check before I mess with the AFM spring tension.

 

cheers

 

Rich

Edited October 16, 2013 by roccorich

[welshpug 1,621]

30 psi is barely over 2 bar, not nearly 3! 2.8 is 40 psi.

 

Though was that with the vacuum pipe connected?

[roccorich 16]

Damn. I was so excited at finding I had the right adaptors and connectors to hook up the guage I forgot to disconnect it.

 

Ill have to do it again tomorrow...

 

cheers

[roccorich 16]

Ok I checked the guage I used last night and it was 40 psi not 30 so pressure is ok even if I did leave the vacume pipe on.

 

Ive checked the ecu tem sensor and its resistance at room temp and in boiling water match what they should be. Havent got a thermometer so cant check the readings in between.

 

So tomorrow Im gonna check the AFM with a multimeter.

 

If the AFM resistances are wrong will adjusting the spring tension change them? Is that how it works?

 

Cheers

 

Rich

[DamirGTI 323]

Not really , spring tension has nothing to do with the AFM sensor plate resistance reading .

 

I wouldn't bother with resistance checking as such , rather that that test the AFM as described in this article (analogue multimeter would be better if you have one) :

 

http://www.the944.com/afm.htm

 

... this way you'll know for sure if it's good or "bad" , if the carbon track isn't severely damaged/worn out it's function can usually be successfully resorted by retracking .

 

If the spark plugs are white colored (white , kinda crystallized layer on the spark plugs can also be sign of the head gasket failure , particularly if you can also smell antifreeze odor from the spark plug tips and from the cylinder/cylinders).. do not drive the car until you sort that out cos it can hurt the engine badly .

Also , spark plug reading by color for mixture quality is a bit hit and miss - for WOT mixture reading you need to run the engine as closer up to the rev limiter and then shut it off by key and coast down until stopped without using engine power and then removing the plugs for check ... color reading by pulling them out after the engine was previously running at idle will generally give you idle mixture coloration .

To make this more complicated ! you suppose to have new plugs and good magnifying glass and reading the plugs by looking deep down below where the center ceramic portion meets metal part of the plug - there will be an ring mark left from the burnt mixture on the ceramic part , and it's color shade (darker-brighter) ring thickness and ring position/level appearance on the center ceramic portion will be indication of the mixture quality . It's also possible to roughly read ignition timing angle from the top earth tip of the plug , by looking at the position of the discoloration gap travel starting from the bottom till the top/end of the earth tip .

 

Check the AFM idle mixture screw (on a 1.9 AFM , as a rule of thumb , the screw must be preset 7 full turns up from the bottom end point) , spring tension - mark current position , unhook the clip which holds toothed ring in place and hold toothed ring with your fingers so that it doesn't roll off around !! then try adding one by one tooth's more from the initial spot in counter clockwise directions (counter clockwise = rich side / clockwise = lean side ) .

Can go safely 4 tooth's more from initial spot in order to tweak up the mixture on the rich side , but start by adding one tooth more and see what happens as just one tooth more on either side has quite a bit effect on the mixture (providing that the AFM was initially preset correctly or at least near to the required spec. of the spring tension) ..

 

If you have or can borrow an wideband lambda sensor with the gauge , this way you'll be able to read out the present mixture quality and adjust the AFM spring tension precisely as/if needed .

 

Did you check the injectors ? they cod be clogged up if not cleaned in the past , and also if they're the right ones for the engine .

It'll be bad approach/"masking a problem" tweaking the AFM spring tension in order to richen up the mixture if there's something else which makes it run lean ..

 

D

Edited October 18, 2013 by DamirGTI

[roccorich 16]

The injectors are the yellow ones. If I take them out and crank the engine over with them in a jar I guess I can check the spray pattern that way.

 

Are they simple to remove?

 

The car will have been running lean since Ive had it as Ive done nothing to cause it so its probably been driven a lot like it.

What sort of damage can it cause? I know it runs hot when its lean.

 

cheers

 

Rich

[roccorich 16]

Ok so Ive had them out and heres a video of one of them. This is with the AFM fully open. Looks ok to me. They were all like this.

 

http://static.photobucket.com/player.swf?file=http://vid783.photobucket.com/albums/yy111/dozzum/20131018_160818.mp4

 

 

[DamirGTI 323]

Yup , the injector spray looks fine

 

Can you take a photo of the spark plugs ?

 

D

[roccorich 16]

Heres a photo I took in the dark the other night.

 

[DamirGTI 323]

That really does look white , however it's not the best photo angle cos i/we can see the discoloration on the actual tip and porcelain part of the plug rather than that , it's just the ground tip that is visible on that photo ..

 

Can you make another shot of all the 4 plugs ? position them this way and take a shot :

 

 

 

(this ones on the pics are from correctly adjusted engine , just a tiny touch on the rich side which was better for this particular engine , and with correct adjusted ignition timing angle)

 

D

Edited October 19, 2013 by DamirGTI

[roccorich 16]

 

Havent had chance to get the plugs out but found one of the old ones in my garage.

Edited October 19, 2013 by roccorich

[roccorich 16]

Not going to be able to do much with the car till the end of next week now and ive got the exhaust manifold to change aswell.

 

But I guess Im going to need to look inside the AFM and see whats going on.

[DamirGTI 323]

Ditto , also suspect that someone has been tempering with the AFM spring tension . Cod be that they wanted to richen up the mixture but ended up turning the spring tension other way around (clockwise = lean side ) by mistake .

 

Try to loosen the AFM spring tension to rich up the mixture (counter clockwise , up to 4 tooth's more from the current spot) , and unwind the AFM mixture screw 7 turns from fully down .

 

Then take it for a spin and remove the spark plugs afterwards and have a look - they need to be grayish to light brown color .

 

Do you have someone near who can borrow you an wideband lambda sensor along with the gauge ? this will be of massive help to you for checking/monitoring the mixture (on board , while driving) so that you can see whats really happening with the mixture trough all the rev range , and you'll be able to adjust the mixture precisely ... way more accurately than tweaking the mixture by reading the spark plugs .

If nothing , 4 wire narrow band lambda sensor hooked up to the multimeter would also be better than adjusting the mixture by spark color reading (narrow band sensor will be precise for checking/adjusting the mixture on low/mid revs , however on high revs/full load it's kinda inaccurate but not so much that you'll be way off the safe side of mixture quality)

 

If the ECU temp. sensor and its wiring are fine , injectors and injectors wiring , if AFM also turns up to be good i'd be tempted to try another/known good spare ECU (not common for them to fail , but who knows) .

 

D

Edited October 19, 2013 by DamirGTI

[roccorich 16]

Idle screw is about 7 turns out at the moment.

 

The AFM is currently sealed with clear sealant so is that how it would be originally.

 

I should be able to borrow one of those Gunson gas analysers.

 

Ive found this article about AFM adjustment that talks about two adjustments. The main spring tension that changes the mixture all through the rev range and another that just effects the higher revs.

 

It also gives a method for adjusting by ear by deflecting the wiper arm each way to see which way makes the revs increase so you know whether to richen or weaken it.

 

http://www.itinerant-air-cooled.com/viewtopic.php?t=7761

[jackherer 543]

Clear sealant is a sure sign someone has been messing with it.

[roccorich 16]

Well I suppose thats a good thing if it confirms I am right to suspect the adjustment is wrong.

 

Cheers

[DamirGTI 323]

Nice article about AFM adjustment

 

Though , i'd advise to skip this first step of wiper arm adjustment : "A) Static Adjustment:" (if the the screw is still intact and has factory blob of sealant on top) , and simply go for spring tension adjustment as described by : "B) Dynamic Adjustment:"

 

From what i've seen during the time on spare bought AFM-s , if it was previously opened and adjustments where done to it was always the spring tension tweaking . I personally haven't yet seen one with adjustments been made by re-positioning the wiper arm as all of them had wiper screw intact and covered with factory sealant .

 

D

Edited October 19, 2013 by DamirGTI

[roccorich 16]

Ye I thought it was well written.

 

Its obviously been written by and for people that are used to carbs but to be fair the method makes a lot of sense.

 

 

Thats a good point about the blob on the wiper arm adjuster, the less I have to mess with the better.

[roccorich 16]

Ok so Ive had a play with it tonight.

 

Got the cover off the AFM and the blob of glue was still in place on the wiper arm arc adjuster so I gave that a damn good avoiding.

 

The wiper track had no white worn through bits but I wanted to adjust it onto a new bit of track anyway. I undid the clamp and tried pushing down on the mech but it seemed like the whole spindle was moving down rather than the clamp. It may have moved but not sure.

 

Then I unwound the spring tension 4 teeth and put it back in the car.

 

Started it up and once it was warm had a go at moving the wiper arm either direction to see if the revs increased.

 

Couldnt detect much difference at idle even with my multimeter measuring RPM.

 

So I wedged the throttle open at 2600 RPM and tried again, this time when I moved the arm anticlockwise it made the revs climb very noticeably so I richened the mixture on the AFM another two teeth.

 

Did it again and it was still revving higher with more fuel so went another tooth.

 

Now when I move the wiper either way at 2600 RPM it doesnt seem to change so I think Im close.

 

Gonna leave it like that for now and see how the plugs are after Ive driven it for a bit.

 

Got the exhaust manifold to do next before that busts wide open.

Edited October 24, 2013 by roccorich

[DamirGTI 323]

As you richen the mixture by adjusting the AFM spring tension , afterwards , you need to re-adjust the idle screw (big brass air screw) in order to compensate for the new settings .

Also the AFM mixture screw , 7 turns from fully down is kinda common setting which i found on the 80% of the 1.9 AFM's , however in your case it may need different adjustment , so try 1-2 turns more out .

 

Further fine idle adjustment you must do after you've finished with the mixture adjusting via AFM , and with all electrics turned ON (lights , heater/blower , rear demister etc.) load the system then adjust the idle speed .

 

As for retracking , when you unhook the wiper in order to "extend" it's travel you'll need to , well , bend it a bit .. so , when you unhook it pull the wiper off the shaft and bend the tip slightly , slide back on the shaft , push down and see if it's moved up to the fresh carbon track surface and the most important - the wiper arm tip must not be adjusted tight against the carbon track so that you actually can hear it rubbing while moving cos it'll cut grooves on the track , rather than that try to adjust it with a minimum load against the track .

I rather do this retracking job by re-positioning the resistor plate , by undoing 4 phillips screws and moving the plate up or down from the wiper arm center .. There's not so much movement available , but i found it to be enough .

Just be careful with unscrewing the phillips screws holding the plate - they're really tight , kinda sized inside the aluminum threads so use best screwdriver which you have or better still small ratchet with extension for undoing phillip screws .. otherwise you'll end up rounding of the screw heads and need to drill them off .

 

Another useful article about DIY mixture adjusting for vane type AFM's :

 

http://www.autospeed.com/A_109878/cms/article.html

 

D

[roccorich 16]

Cheers thats a good guide.

 

I did wonder if you could move the circuit board. That seems a much safer way Although like I say its not worn through the track yet.

 

Once Ive done the exhaust manifold and the plug colour looks about right I can try getting tbe timing right then come back to fine tune mixture.

 

Arnt old cars just fun ...

[DamirGTI 323]

Just be careful with the screws holding the board , even when you do get them moving theres no guaranty that some of them wont snap ! and care not to scratch the board with the screwdriver if said scenario happens .

 

I always end up with one or two of them snapping , but even if they snap , two remaining screws are enough for tightening the board back securely .

 

Have fun

[roccorich 16]

Spent several hours adjusting the mixture and driving about checking the plug colour.

 

Finally got the plug looking like this.

 

Thats 16 teeth richer!!

[roccorich 16]

Really need to get a lambda probe or gas analyser of some sort on it now to see how it is all through the revs.

 

I think its a bit rich at idle but Id rather the car be richer than lean for now.

[DamirGTI 323]

Can you do a top shot please ?

 

Is there any black sooty deposits on the outer metal part of the plugs ?

 

D