2.0 L petrol idle speed adjustment

Technical questions and answers about the Mazda Bongo

Moderators: Doone, westonwarrior

User avatar
mikeonb4c
Supreme Being
Posts: 21582
Joined: Sun Nov 05, 2006 10:49 pm
Location: Living with Mango Bongo in the North West but with a tendency to roam
Contact:

Re: 2.0 L petrol idle speed adjustment

Postby mikeonb4c » Thu Apr 20, 2017 6:38 pm

Andrewpridmore wrote:
mikeonb4c wrote:I have a sort of cruise control on my Bongo. It works by having a cable that is attached to the throttle lever and that can be locked. It is handy also if i want to raise the tickover. Is the OP able to raise tickover by slightly depressing the throttle. If they are, is there any way the throttle lever can be persuaded to rest in this new position? I do agree that any underlying problem should be addressed but I'd be curious to hear views regardless.


I've manually set the throttle cable adjusters to force an idle rpm of around 1000 but as soon as i engage drive (or anything other than neutral or park) the revs dive to 500 or less, as if the engine can't handle any initial load. Put it back into park or neutral and the revs go back up.


OK, scratch that thought :(
I Bongo, therefore I am...
Bongoing, BonGoing, BonGone
Andrewpridmore
Bongonaut
Posts: 26
Joined: Wed Apr 19, 2017 7:27 pm

Re: 2.0 L petrol idle speed adjustment

Postby Andrewpridmore » Thu Apr 20, 2017 11:02 pm

Nightmare of an evening:

I cannot get to the throttle body because the location on the 2L engine is inside a load of sheet metalwork. I got the rear plate off but even that wasn't adequate to detach any hoses. if i had a well lit garage, several hours, a Haynes manual & was willing to I'll all the metalwork, handbrake, etc. apart it could be possible but no chance on the street with a few hours of light to work by.

Vacuum hoses looked fine and I sprayed all over with carb cleaner with zero results so doubt there are any cracks or splits etc.

I took it on a blast to try and work some of the redex through. All I achieved was the bongo almost dying on 2 minor hills because the revs wouldn't go up (going too slow when i started going up them). It just started to stink of burning oil (or a slipping belt?) on a steeper hill whilst it sat almost stationary.

As soon as it was back on the level she would shoot off like nothing was wrong. This is the first time I've seen such problems on a hill so things are getting worse - usually hills aren't lightning fast but they've never been a problem. I also found that if i turn the AC on, the acceleration cannot pick up when moving for stationary - it stays crawling along. Turn the AC off and it starts to pick up speed. This all only applies to an rpm below 1500 or so - once I'm over that, hills and AC are no issue. The bongo just doesn't want to go from 500-1500rpm, especially if there's any sort of incline involved. Even got beeped taking ages to pull away from lights where there was a 5-10° incline :oops:

Checked brake discs, warm but not sizzling hot after i got back. Can't adjust throttle cable any further than it already is (not that it makes any difference, as the revs drop to 500 again as soon as it goes into gear - do the revs always drop when it goes into gear? I don't recall the revs dropping originally)

There's a healthy level of pressure coming from the tailpipe (hand test)

Next steps are to fire a load of carb cleaner up at the throttle body from as close as i can get after the airbox + change the spark plugs.

Any thoughts would be appreciated - it's such a distinct set of stuff that there can only be a couple of causes for it to appear all of a sudden.
I did change the oil 2 weeks ago but can't see any connection there...
2.0L 2003 tin top aero city runner, LPG, unconverted (those rear seats are comfy enough!) :D
User avatar
Northern Bongolow
Supreme Being
Posts: 7068
Joined: Mon Mar 15, 2010 11:33 pm
Location: AKA Vanessa

Re: 2.0 L petrol idle speed adjustment

Postby Northern Bongolow » Fri Apr 21, 2017 3:13 am

dont use carb cleaner on the throttle body sensors, (just squirting up the mouth) it needs to be proper sensor cleaner, carb cleaner on a warm sensor may knacker it. its ok on the body though.
Bongolia
Supreme Being
Posts: 1400
Joined: Fri Apr 01, 2016 2:17 am
Location: London
Contact:

Re: 2.0 L petrol idle speed adjustment

Postby Bongolia » Fri Apr 21, 2017 6:04 am

It could be a number of things,blocked exhaust,egr fault (if fitted) low fuel pressure,ignition HT, AFmeter,Ox sensor,ecu fault, box related and then there is the LPG side possible interaction?

Is there a garage you could get to look at it?
Might save yourself a lot of aggro in the end.
Andrewpridmore
Bongonaut
Posts: 26
Joined: Wed Apr 19, 2017 7:27 pm

Re: 2.0 L petrol idle speed adjustment

Postby Andrewpridmore » Fri Apr 21, 2017 8:19 am

This morning i changed the spark plugs (quite dirty/tan but nothing hideous) and things were even worse.

In drive pulling away it was like it was in neutral on a gentle slope, totally gutless and took a fair bit of coaxing to get it above 1000rpm. After that she happily picked up as if nothing was wrong. Could the first gear have an issue but none of the other gears? Am clutching at straws here!

Have called breakdown as i don't think it's safe to drive (not safe for the state of other drivers mental health and​ patience...) So will see what he says then if he can't find anything a I will get her taken down to Brighton - she was having belts changed at John Moore on Friday so will see if they can have a look before then.

Totally frustrating that the problem only exists at one specific time which is also the time other drivers have the least patience :roll:

I did have a thought about first gear having the issue but holding it in second and reversing are both as gutless. If i could force the idle above 1000rpm (or just stop it diving to <500rpm when drive is engaged) then i reckon it would be fine... Though that was the point of the original post :lol:
2.0L 2003 tin top aero city runner, LPG, unconverted (those rear seats are comfy enough!) :D
Bongolia
Supreme Being
Posts: 1400
Joined: Fri Apr 01, 2016 2:17 am
Location: London
Contact:

Re: 2.0 L petrol idle speed adjustment

Postby Bongolia » Fri Apr 21, 2017 10:56 am

Andrewpridmore wrote:This morning i changed the spark plugs (quite dirty/tan but nothing hideous) and things were even worse.

In drive pulling away it was like it was in neutral on a gentle slope, totally gutless and took a fair bit of coaxing to get it above 1000rpm. After that she happily picked up as if nothing was wrong. Could the first gear have an issue but none of the other gears? Am clutching at straws here!

Have called breakdown as i don't think it's safe to drive (not safe for the state of other drivers mental health and​ patience...) So will see what he says then if he can't find anything a I will get her taken down to Brighton - she was having belts changed at John Moore on Friday so will see if they can have a look before then.

Totally frustrating that the problem only exists at one specific time which is also the time other drivers have the least patience :roll:

I did have a thought about first gear having the issue but holding it in second and reversing are both as gutless. If i could force the idle above 1000rpm (or just stop it diving to <500rpm when drive is engaged) then i reckon it would be fine... Though that was the point of the original post :lol:


Straw clutching :)
It would be best to get it down to your guy I reckon for your own mental state if nothing else. :D
Hopefully it will be something straight forward. [-o<
Do keep us posted on the outcome.
Andrewpridmore
Bongonaut
Posts: 26
Joined: Wed Apr 19, 2017 7:27 pm

Re: 2.0 L petrol idle speed adjustment

Postby Andrewpridmore » Fri Apr 21, 2017 11:21 am

Breakdown man says it's the distributor cap /rotor - dirty and even when cleaned it was no good - too large a gap for the spark so it got worse (1st good sign we did something that made it obviously worse!)

Now down at county cars of sussex in Brighton who has fitted me in at short notice and is going to try a cap off another bongo so might be back on the road by noon :-)
2.0L 2003 tin top aero city runner, LPG, unconverted (those rear seats are comfy enough!) :D
Bongolia
Supreme Being
Posts: 1400
Joined: Fri Apr 01, 2016 2:17 am
Location: London
Contact:

Re: 2.0 L petrol idle speed adjustment

Postby Bongolia » Fri Apr 21, 2017 11:43 am

Andrewpridmore wrote:Breakdown man says it's the distributor cap /rotor - dirty and even when cleaned it was no good - too large a gap for the spark so it got worse (1st good sign we did something that made it obviously worse!)

Now down at county cars of sussex in Brighton who has fitted me in at short notice and is going to try a cap off another bongo so might be back on the road by noon :-)


Tricky things engines :?
Fingers crossed but it sounds right! [-o< [-o<
I can almost feel your sense of relief from here!
You should treat yourself to a celebratory run out this weekend. :P

FMI has your vehicle a separate ignition coil?
Andrewpridmore
Bongonaut
Posts: 26
Joined: Wed Apr 19, 2017 7:27 pm

Re: 2.0 L petrol idle speed adjustment

Postby Andrewpridmore » Fri Apr 21, 2017 2:55 pm

Had to take it to County Cars of Sussex in Portslade, Brighton in the end. He fitted me in at short notice and swapped the whole distributor unit out with a known good one & the bongo is probably the fastest she has ever been =D>

However...

The distributor died because it was getting fried in the heat from a blowing exhaust (no obvious defects or holes, seems to be from the 4 exit pipes that are just tacked on in 2-3 places rather than being solidly welded). Both breakdown man & Colin at County Cars reckon it needs proper welding but am asking myself "isn't that what gun gum & exhaust bandages are for?!" - thoughts? Welding seems overkill & i could gun gum around the gaps in a few minutes.

Also the crankshaft pulley is a little wobbly which he said could be messing up the timing (i think that's the gist of what he said...) So will get that changed/looked at when belts are done next week. He reckons it will be even more nippy then.

Am very pleased to have her back in the land of the living.

Now, gun gum or welding? Hmmm...
2.0L 2003 tin top aero city runner, LPG, unconverted (those rear seats are comfy enough!) :D
Bongolia
Supreme Being
Posts: 1400
Joined: Fri Apr 01, 2016 2:17 am
Location: London
Contact:

Re: 2.0 L petrol idle speed adjustment

Postby Bongolia » Fri Apr 21, 2017 5:33 pm

Welding m8 deffo. Has yours a heat sheild?
https://goo.gl/photos/JEgCqZaRFpgBeG3V7
Crank pulley has major sensor reading from it so thats a deffo too.
Happy days.....
Just lugged mine up Detling Hill for the show and thought of you as it dropped into 2nd gear!
Do you know if it has seperate ingnition coil?
Andrewpridmore
Bongonaut
Posts: 26
Joined: Wed Apr 19, 2017 7:27 pm

Re: 2.0 L petrol idle speed adjustment

Postby Andrewpridmore » Sat Apr 22, 2017 12:26 pm

This morning i found the blow at the joint where the 4 pipes come together & are bolted to the rest of the exhaust, just at the bottom of the heat shield. Have fun gummed around it.

Funny thing was the rev counter then stuck at zero for a minute after starting :-/

She's gone sluggish again, won't idle above 300-400 rpm and is a little slow to get moving especially when getting going uphill.

Starting to think/hope the chief culprit will be the pulley/belts which are due on Friday anyway. Fingers crossed she won't die on me like last week...
2.0L 2003 tin top aero city runner, LPG, unconverted (those rear seats are comfy enough!) :D
Bongolia
Supreme Being
Posts: 1400
Joined: Fri Apr 01, 2016 2:17 am
Location: London
Contact:

Re: 2.0 L petrol idle speed adjustment

Postby Bongolia » Sat Apr 22, 2017 4:45 pm

Have you got a seperate ignition coil.
Did they swop the distributor or just the cap and arm in the end?
Andrewpridmore
Bongonaut
Posts: 26
Joined: Wed Apr 19, 2017 7:27 pm

Re: 2.0 L petrol idle speed adjustment

Postby Andrewpridmore » Sat Apr 22, 2017 10:25 pm

No idea whether it has a separate ignition coil - how would i tell? How would that make a difference?

I think he changed the entire distribution unit, cap, rotor and the bit it goes into. Funny but now i think of it, it was still awful after he changed it & it was only when he altered the timing by rotating the whole distributor unit that it actually improved, so i wonder if it he covered a timing fault up briefly by changing the timing & the distributor was perhaps poor but not the real fault?

I reckon the blowing exhaust was a red herring too, I've located a tiny blow and sealed it and there's bugger all difference.

There is definitely a wobbly crankshaft pulley - will check it is tight tomorrow. Could make sense - wobbly pulley throws out the timing then manually​ tweaking​ timing via the distributor unit pulls timing back in for a short period. I'm hoping if it is the pulley then it's loose rather than knackered, and if it is knackered then it hasn't taken the crankshaft with it. Eternal optimism [-o<

Can i adjust the crankshaft pulley tension or even get at it easily (i.e. From the seat access points) to check for any wobble whilst it's on the ground or would i need a pit/lift & to be underneath it?
2.0L 2003 tin top aero city runner, LPG, unconverted (those rear seats are comfy enough!) :D
Bongolia
Supreme Being
Posts: 1400
Joined: Fri Apr 01, 2016 2:17 am
Location: London
Contact:

Re: 2.0 L petrol idle speed adjustment

Postby Bongolia » Sun Apr 23, 2017 7:54 am

Well thats a dissapointment. :(
Count the leads coming from dist to plugs.
4=internal coil 5=external. On the 626 Mazda (same engine not sure on dist) the internal coil type suffered with ignition amplifier failure ( Mazda term is ignitor pack) this could show in a number of ways but mainly non start or misfire. If they swopped over the entire dist, body as well, it is unlikely to be that.
I would think they tried to tighten the pulley at the time of your visit. It is probably the rubber cush thats failed. Excessive vibration here could send a fluffy signal to the ECU, that would need a scope to see that.
Best to get it back to them and let them sort it when they do the pulley.
They will have a few bits they could substitute for testing purposes like AF meter etc.
I think other posters on here use County Cars from memory, I think they are well thought of.
Andrewpridmore
Bongonaut
Posts: 26
Joined: Wed Apr 19, 2017 7:27 pm

Re: 2.0 L petrol idle speed adjustment

Postby Andrewpridmore » Sun Apr 23, 2017 7:48 pm

Distributor cap has four wires going out to plugs around the edge and another wire in the middle going off to a box on the far left of the vehicle that has a few other electrical plugs running to it. Looks the same as every other 2.0L cap I've seen photos of.

I had to call recovery again as bongo couldn't even make it up a 15° slope 3m long, even with a run up. Total loss of power and was either holding still or rolling back down the slope in D, S & L, with or without hold. Revs fine in N & P. Checked distributor & it's fine.

This time he thought it was crossover of the fuels - that the setup of one was affecting the other, despite that it affects both fuels. I wasn't convinced about this - it was running fine on both after the distributor/timing fix on Friday then it seems to have gone bad again.

We delayed any transport until tomorrow morning. I will call John Moore in Brighton (where belts are due on Friday) to see if they can look at LPG & if so I will get her taken down there. Other options include my LPG fitter up here but as I say I wasn't convinced about his "crossover of fuels" theory as this has happened in the last 2 weeks when the LPG has been on there for almost 3 months. He mentioned damaged valves and seats which on a top of the range LPG system running flashlube for such a short time I find quite unlikely. I felt he was clutching at straws even more than me :lol: i only get one free transport with breakdown so i go take it to my LPG fitter here (Kent) and it isn't the LPG then that's £300 to take it down to Brighton for the belts and pulleys. Tough one.

He didn't think the crankshaft pulley was too bad & did point out that it revved fine and was just a low revs problem with rough idle and misfire which vanished when it was revved. He checked vac pipes & said plugs and leads must be fine or misfire problem would persist at higher revs.

So a misfire (both breakdown guys said it sounds like it's on 3 cylinders at idle) and bad idle, rpm drops further under any load, yet it all goes away once over the 1000-1500 rpm zone.

Anyone had any experience of LPG causing such an issue? He reckoned he's seen loads of petrol bongos and never seen anything like it, hence he places the blame on the LPG. I have had a couple of stalls on LPG - stopping quickly or reversing has stalled it on several occasions ever since it was fitted but i had put this down to my hamfisted driving technique​ :oops:
2.0L 2003 tin top aero city runner, LPG, unconverted (those rear seats are comfy enough!) :D

Return to “Techie Stuff”

Who is online

Users browsing this forum: Google [Bot] and 6 guests