V6 LPG chugging / clonking / low power

[mr_marrakesh]

Hello knowledgeable Bongo people. I started my LPG converted V6 about a month ago and it made a chugging noise. It was also intermitantly very low on power and would chug along slowly and then accelerate away then chug, etc until the engine was up to temperature and then it was fine. One time it was made quite a loud clonking noise going up hill when I put my foot down. Sounded like someone banging a hollow tube on the underside of the van but it was definitely engine related as it didn't happen going over bumps but when I put my foot down (I quickly took it off again). This has all been happening when it's cold but the other day I got the dreaded clonk when going up a hill when the engine was warm and everything else seemed hunky dory.

For a long time (at least two years) it intermitantly has an unsteady idle (hunting?) when the engine is warm (never when cold). Very occasionally it stalls when stopped or maneuvering. I live with it but am wondering if the two could be related. I mentioned this to my mechanic as it was due in for a service and he had a quick look over it and said I should get a new air flow meter and he would fit that when he did the rest of the service. Sounded ok until I found out they're circa £615 so I thought I better be sure before getting one.

I also get an intermitant rapid quiet clicking noise when the accelerator is pressed. From reading other posts I think this may be carbon canister / EGR / injectors / evap valve (I don't know what any of these are). It doesn't bother me, just wondering if it's related.

Oh also I've read posts about loosening the petrol cap. I've never done it but I do get a wooshing noise when I undo it. Am I getting a vacuum in the tank? Is this a problem? Should I try loosening it?

Don't think it's ignition related as I had a full set of new ignition parts just over a year ago but who knows.

Sorry for long post, thanks in advance for any help you may be able to offer.

[mr_marrakesh]

Sorry, should have said. Switching to petrol doesn't help any of the above complaints.

[haydn callow]

It won't be the petrol cap as it happens when n LPG.....suspect you need to do a overhaul of the ignition system which needs to be tiptop for LPG.... check out the plug leads at the spark plug end....any damage will cause a serious misfire....then move on to the plugs themselves.dizzy cap and rota arm......only use quality parts.

[haydn callow]

Just read the last line of your post...still think my advice is worth checking out.

[rita]

Might be worthwhile having you mechanic checking the Hydraulic Lash Adjusters, if these are losing temp pressure the vehicle could respond as you have mentioned. Also a compression test would not do any harm.

Good Luck.

[mikeonb4c]

Might be worthwhile having you mechanic checking the Hydraulic Lash Adjusters, if these are losing temp pressure the vehicle could respond as you have mentioned. Also a compression test would not do any harm.

Good Luck.

In case, like me, you're an old fogey out of touch with new terminology, I discovered that

"A hydraulic valve lifter, also known as a hydraulic tappet or a hydraulic lash adjuster, is a device for maintaining zero valve clearance in an internal combustion engine. Conventional solid valve lifters require regular adjusting to maintain a small clearance between the valve and its rocker or cam follower."

Phew - turns out i do know what it is.

Mind you, the OPs symptoms got me thinking more about misfiring and pinking, as the only reports i've read/heard about worn hydraulic tappets on a v6 Bongo noted increasing tappety noise as Bongo warmed, but no obvious loss of power. But, leave no stone unturned i reckon.

[rita]

I bow to your Superior Motor Engineering expertise after 20959 posts you are bound to learn something.

There was a case recently when a highly experienced bongo mechanic could not get a V6 started, after Nine Weeks and a set of HLA the magic happened.
The HLA are crucial to this engine.
From one old foggy to another auld foggy.

Take care.

[mikeonb4c]

I bow to your Superior Motor Engineering expertise after 20959 posts you are bound to learn something.

There was a case recently when a highly experienced bongo mechanic could not get a V6 started, after Nine Weeks and a set of HLA the magic happened.
The HLA are crucial to this engine.
From one old foggy to another auld foggy.

Take care.

Quite the reverse. You're the pro here and i think the stone you've identified should defo be overturned, and sooner rather than later if not too costly to test. I vaguely recall that case and it was grim. Did it go on for so long i wonder because no-one wanted to spend that amount of dosh without certainty over a successful outcome? Then again, and with hindsight, could testing sooner have established what work needed to be done.

Blimey have i done that many posts - you can't see the figure like you used to on the old forum.

Edit: i managed to find the post about tbe incident in question, in case its if use to the OP:

http://igmaynard.co.uk/bongo/forum/view ... ilit=japan

[mr_marrakesh]

Great, thanks everyone, I read the post about the Bongo that needed new tappets / HLAs, interesting but I hope mine doesn't too! I've got a few things to talk to my mechanic about anyway. I don't think I'll be buying an air flow meter just yet.

One thing my mechanic complains about a lot is that he can't get the Bongo "onto the computer" to find out what's wrong with it because it's an import. Are there garages (on the Bongo friendly list perhaps, none of which are very near me) with computers which will work with a Bongo or are they just too old for all that modern computer rubbish?

[Bongolia]

I have been lurking on this one. My experience with LPG is confined to filling lighters and cooking on camping gas stoves.
However I dont think this is an LPG issue so here is my two Bobs worth.
The big clue here is.. the fault is not there(or didn't use to be there) when the engine is hot.
As for the scanner/computer, on our vehicles they should be regarded as giving an indication of where the problem may be. Our systems are not as sophisticated as the later systems and sometimes can lead you up the garden path if you depend on them entirely for the diagnosis.
http://igmaynard.co.uk/bongo/forum/view ... 47#p686747
So what makes your mex believe its the air flow meter, I am not saying it isn't, but has he tested it before failing it and how?
Swapping bits out is OK if you have one under the bench else it can work out an expensive method (for the customer)of fault finding and may still not resolve the issue.
If you have no Bongo garages near you (who may have one under the bench!) consider using someone who specialises in engine management/ fuel injection. Our Bongos are quirky but you don`t need a scanner to find the faults more a systemic approach to the problem.
Whereabouts are you?
Good Luck.

[windywatson]

Hi,

You said:-

"For a long time (at least two years) it intermittently has an unsteady idle (hunting?) when the engine is warm (never when cold). Very occasionally it stalls when stopped or manoeuvring. I live with it but am wondering if the two could be related. I mentioned this to my mechanic as it was due in for a service and he had a quick look over it and said I should get a new air flow meter and he would fit that when he did the rest of the service. Sounded ok until I found out they're circa £615 so I thought I better be sure before getting one".

I have a V6 that exhibits exactly the same problem as above, although mine does only tend to be after very long journeys, hence well warmed up. Having read about similar issues on the forum I also came to the conclusion that it pointed to an air flow meter. As you rightly say they are very expensive so need to get a definitive diagnosis before purchase. However I would say that there are good breakers of Bongos now, so worth the purchase of a second hand one I would have thought. Also have read somewhere that the same unit has been used on other Mazdas. So may be worth some research and visiting a scrap yard for a unit.
I have a second V6 & when I next use go on my holidays (currently the camper with the problem it is SORN for winter) I intend to swap the air flow meter over van in order to prove if that is actually the problem.
The one thing I did do that helped reduce the problem was to fit a scavenger fan override switch so that I could reduce the engine bay temperature myself when on long journeys. This seems to help reduce the symptoms. so points to temperature having an effect on the problem some how.

Perhaps you have a member near you with a V6 that may loan you their air flow meter in order to eliminate or confirm it to be that. Could save you some money.

[mikeonb4c]

A really useful post Windy. And how interesting about lowering engine bay temperatures helping the problem. I fitted a scavenger fan over-ride at least in part to help the engine ancillaries, though mainly to help the occupants.

[windywatson]

Following on from my other post I found the following info that sort of fitted the symptoms. This info was taken from the following resource:- http://www.random-misfire.com. This site has some interesting reading with good advice on what to look for when fault finding.

A rough idle or stalling. A large vacuum leak can lean the air/fuel mixture out to such an extent that an engine will not idle at all. An EGR valve that is stuck open at idle can have the same effect as a vacuum leak. So too can a loose positive crankcase ventilation (PCV) hose, a leaky PCV valve or the wrong PCV valve (one that flows too much air for the application). If somebody replaced the PCV valve recently, they may have installed the wrong PCV valve. The rough idle in all of these cases is caused by "lean misfire." The fuel mixture is too lean to ignite reliably so it often misfires and fails to ignite at all.

Reading this, air leaks could be a good place to start when looking for problems as described in the original post.

[mr_marrakesh]

It sounds like my Bongo might have the same problem as yours windywatson. Mine too only normally exhibits the idle problem after a longish journey. I'm coming to the conclusion that this isn't related to the chugging / clonking when cold problem. I think my mechanic thought a new air flow meter would probably solve the idle problem and might help the other but I'm not willing to take a chance on so many probablys and maybes.

I live near Alnwick in Northumberland. When I first got the Bongo I looked at the Bongo friendly garages list. There's one in Cramlington 25 miles south of me and one in Berwick 30 miles north. I thought about using one of them but neither of them were listed as V6 service garages so I decided it wasn't worth the hassle of going so far.

[mikeonb4c]

I think the 'Bongo friendly garage' label can get over used. Unless its one of the handful of people who deal almost exclusively with Bongos and see enough of all engine types, they may do no better at tracking down this one than a garage that sees a lot of v6 engines etc. I think fitting a scavenger fan over-ride switch and engine block temp gauge could be interesting/worthwhile regardless and might just help the problem.