2.0 petrol stalling when idling or braking

Technical questions and answers about the Mazda Bongo

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tiffer
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Re: 2.0 petrol stalling when idling or braking

Post by tiffer » Sat May 06, 2017 9:09 pm

Bongolia wrote:
In a way that is a bit of a disappointing result. :(
When the engine is presented with an additional load the idle should automatically increase to compensate for that load so you would expect to see a momentary drop in RPM and then it rise again to a stable idle.
So we need to prove whether the idle speed control system is working properly or not first.
In a nutshell load the engine up with as as much as you can as fast as you can with the engine in a warm but not at normal running temp this when the ISC would be taxed the most. An octopus may be useful here. :)
If you can try it again this time do it with engine partially warm and put it into drive whilst putting everything on headlights, rear screen, AC on full cold rear and front blowers etc and watch the rev counter to see the effect.
Ignore the rough idle and the jump in rpm when you try and raise the revs for now.
I tried this and the revs did drop but recovered almost instantly, it's making me think the issue isn't electrical but maybe more engine related, injectors perhaps?
Bongolia
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Re: 2.0 petrol stalling when idling or braking

Post by Bongolia » Sat May 06, 2017 9:39 pm

So put aside the ISC for now take a look at the rough idle and the jump in RPM.

Take off the dissy cap and inspect it for condition.
Look at the king pin pin ( thats the black column with the brass cap) where this enters the cap you should see a spring it should be clean with no signs of arcing, the four pick up pillars are they all good, is the cap clean inside with no tracking trails and is there any movement in the shaft when you try to move it from side to side. If all that looks good re assemble.Clean the cap externally and wipe down the leads and HT caps. Any doubt post a pic.

Next run the engine up to temperature and hold the revs at 2500 for a minute or so and then switch off the ignition at that RPM.
Remove the spark plugs keep them in order and note the colour. Are they all the same colour if not (with cylinder one being the front one ) note which are different lighter or darker ? Pic here would help.
Look at the centre electrode porcelain portion for marks and cracks check the outer porcelain for the same if they all look OK clean & gap them all evenly and stick them back.

Have you a multi meter. If not you need to borrow one.
On the side of the throttle body at the back of the engine you will see the throttle potentiometer.

https://goo.gl/photos/3nYyF2rE3TCgcWWV7
Remove the plug and inspect the wiring to the plug for any damage or hardening of the cable.
Next using the multi meter place one probe onto the centre pin of the pot and the other on the either of the outer pins. Slowly depress the throttle pedal until you reach its stop.
You should see the resistance rise or fall (depending on how you have the probes) steadily with no sudden changes. Pay particular attention at the first part of the check.
If that`s OK check the idle circuit switch this is a single wire plunger switch with the meter check that this switches on and off.
How did that go?
tiffer
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Re: 2.0 petrol stalling when idling or braking

Post by tiffer » Mon May 08, 2017 1:04 pm

Yikes! that's taking me into the realms of "knowing what your doing"! but i'll give it a go and let you know the results of my investigations.
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Re: 2.0 petrol stalling when idling or braking

Post by Bongolia » Mon May 08, 2017 2:29 pm

Yes,it might seem a bit daunting but they are basic checks that need to be done first.
And there are a few more after that too. :D
Any doubts post images.
Strangely enough mine cut out as you describe on Sunday but Sunday was a strange day for me. :?
Good luck.
tiffer
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Re: 2.0 petrol stalling when idling or braking

Post by tiffer » Mon May 08, 2017 10:11 pm

Ok, I've had some success. I checked the distributor cap and I think it looked alright?

Image

Image

Then I ran the engine for a while at 2500 revs and switched it off at that, then removed the spark plugs and they looked like this

Image

Image

Then I tried to get to the potentiometer but couldn't reach it, do I need to take out the centre part of the engine cover to get at that? if so, there seems to be a lot of dismantling required! I haven't tried but will give it a go if that's the only way.

I decided to replace the spark plugs with new but when I started up the engine it ran even worse than before and cut out after about 30 secs which has never happened before. :-k
wonkanoby
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Re: 2.0 petrol stalling when idling or braking

Post by wonkanoby » Mon May 08, 2017 10:31 pm

if thats the rotor arm in picture 2 it does not look right to me

should be nice clen and shiny

http://mazdabongo.com/catalog/mazda-bon ... st-models/
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Re: 2.0 petrol stalling when idling or braking

Post by Bongolia » Mon May 08, 2017 11:42 pm

Which plug is cyl one in your image.
Go back over what you have done with the dissy.
Have you got the firing order right check against your original image posted on here.
Are all the HT leads ok no signs of damage burns etc are they all clear and not touching metal anywhere. Look inside the top cap of the HT leads where that fit on the plugs do the clips look ok. Is the cap screwed down evenly. If all is yes and problem persists remove the cap,leave the leads attatched, look into the space where the pillar goes is the spring in there i the carbon centre pin there. Replace the old plugs in the original order.Clean up the rotor arm with nail varnish remover and a tooth brush while your there. Whats it like now
tiffer
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Re: 2.0 petrol stalling when idling or braking

Post by tiffer » Tue May 09, 2017 6:56 am

Plug order is 1,2,3,4 left to right
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Re: 2.0 petrol stalling when idling or braking

Post by Bongolia » Tue May 09, 2017 7:29 am

OK. Plugs dont look too bad. Cap looks a little pitted on the pins and rotor is probably due too.
But just put back the old plugs and re check back over what you have done for now.

Where in London are you?
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Re: 2.0 petrol stalling when idling or braking

Post by mikeonb4c » Tue May 09, 2017 9:00 am

What's the mileage? There is an argument for replacing dizzy cap etc as part of routine maintenance every X thousand miles and maybe it'd be worth doing that anyway. Theres been a number of v6 Bongos whose problems disappeared when new cap and quality leads were fitted.
ade33
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Re: 2.0 petrol stalling when idling or braking

Post by ade33 » Tue May 09, 2017 3:09 pm

I'm subbed to this thread as our V6 is doing this too.

Fine while the throttle is open but idle is unstable and the engine hunts to the point of stalling.
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Re: 2.0 petrol stalling when idling or braking

Post by Bongolia » Tue May 09, 2017 4:05 pm

ade33 wrote:I'm subbed to this thread as our V6 is doing this too.

Fine while the throttle is open but idle is unstable and the engine hunts to the point of stalling.
All the checks are generic so you can do the same on yours. The positioning of sensors etc would be different however. Would be less confusing if you could post another like V6 idle and stall and the chaps could pick it up from there.
tiffer
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Re: 2.0 petrol stalling when idling or braking

Post by tiffer » Tue May 09, 2017 9:52 pm

Bongolia wrote:Which plug is cyl one in your image.
Go back over what you have done with the dissy.
Have you got the firing order right check against your original image posted on here.
Are all the HT leads ok no signs of damage burns etc are they all clear and not touching metal anywhere. Look inside the top cap of the HT leads where that fit on the plugs do the clips look ok. Is the cap screwed down evenly. If all is yes and problem persists remove the cap,leave the leads attatched, look into the space where the pillar goes is the spring in there i the carbon centre pin there. Replace the old plugs in the original order.Clean up the rotor arm with nail varnish remover and a tooth brush while your there. Whats it like now
Right, I have checked condition of HT leads and they seem fine, firing order is correct i hope! spring is present in dissy cap and I think the carbon centre pin (is it small and quite short?) old plugs replaced and rotor thoroughly cleaned. Now the engine is searching even more from first firing up and eventually stalling, i have tried this three times and each time it stalled after no more than a minute.
If anything it's much worse than when I started fiddling about!
tiffer
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Re: 2.0 petrol stalling when idling or braking

Post by tiffer » Tue May 09, 2017 9:53 pm

Bongolia wrote:OK. Plugs dont look too bad. Cap looks a little pitted on the pins and rotor is probably due too.
But just put back the old plugs and re check back over what you have done for now.

Where in London are you?
I'm in Ealing, Help!!
tiffer
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Re: 2.0 petrol stalling when idling or braking

Post by tiffer » Tue May 09, 2017 10:06 pm

probably worth mentioning that i did get as far as unplugging the lead from the potentiometer and poked around but couldn't get my multimeter probes to reach properly in the tight space between the engine and cover so I put the plug back in, could that that be the cause of it running worse than before?
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