V6 Engine Missing When Cold. New HT Leads?

[BongoBonkers]

Hello

Our V6 has been quite healthy for a number of years now but has recently started performing poorly when cold. The engine is low on power at low revs in particular and is very lumpy, as if it's 'missing'. This is worse when the engine is cold and gets progressively better as it warms up to the point where it is pretty much cured after 30 minutes or so on the road and then behaves perfectly.

During one very bad incident I parked it up en route and called the AA to look at it. The AA man found the lead from coil to distributor had a badly corroded end and lashed up a replacement from parts old parts he had on his van. This cured it for a while and we then replaced the king lead with a new one when we got back from our trip. The AA man's opinion was that the whole HT lead set would need replacing soon as he reasoned that if one lead was that bad then likely one or more of the others would be in similar condition. Incidentally he inspected the distributor assembly and said it looked good to him...

Now the problem is back and I need to fix it ASAP as we have about 3000m to do over Xmas and New Year. What is confusing me is that the issue does go away once the engine is warm.....does that make any sense? HT leads are expensive and I am cautious to change them on an experimental basis.

Our van has LPG but the problem seems the same on gas or petrol.

Has anyone else had a similar problem?

Another thing I am confused about is that you can get a 6 lead or 7 lead set for the Bongo....How can you tell which you need? Is the 7th lead the one from distributor to coil aka the king lead? Why are some of the leads different lengths?

Hope you can help??????? Thanks

[haydn callow]

I had exactly your problem some time ago...Although it was worse on LPG.....To run LPG your ignition system needs to be 110%.
The 7th lead is the "king lead"
Don't be tempted by aftermarket leads....I spent £70 on them and had to send them back....Mazda ones are very expensive but will last another 10 years..
However.....before you do that.
Have a look inside the dizzy cap.....any pitting on the contacts or rota arm....replace them....this will cost about £50 and could well sort it......easy DIY job and it sorted my misfire.......again get quality parts....I got some junk which I binned

Also have you treated it to a set of plugs ?? Bosh super plus FR7DC YTTRIUM...old plugs are not good with LPG

Differant lengths.....because some plugs are further away from the dizzy than others

[Ian]

Another thing I am confused about is that you can get a 6 lead or 7 lead set for the Bongo....How can you tell which you need? Is the 7th lead the one from distributor to coil aka the king lead? Why are some of the leads different lengths?

To get a full set of genuine Mazda replacements you need the HT Leads (RH), HT Leads (LH) and HT Coil Lead. Bottom 3 items in this section:
http://www.igmaynard.co.uk/bongo/mercha ... #Electrics

You will also find Dizzie Cap & Rotor Arm there as well.

[BongoBonkers]

After some fun investigative work this evening in the dark wind and rain I was overjoyed to discover that two of the contacts inside the distributor cap are so worn as to be effectively not there! I am very pleased about this and have ordered a new cap and arm from the Bongo shop. I will let the AA man off not clocking this fact when he had the cap off a few weeks ago as he was a really nice bloke and it was also dark windy and raining that night but he didn't have the benefit of a garage to be working inside!

Thanks for pointing out checking the cap Haydn. Although it's kind of obvious I had glossed over it as the AA man had already investigated that area. It just goes to show, until you've seen it with your own eyes you can't 100% rule it out. Cheers

[dandywarhol]

Does the engine reappear when it's warm?

[BongoBonkers]

Yes. I can also do mother in laws if the money's right!

[haydn callow]

Do the rota arm whilst your at it or the new cap will soon get burnt on the contacts

[BongoBonkers]

Yes Haydn, have ordered both parts. Ordered online from Ian last night about 9 pm and received email an hour ago to say they're in the post - spot on!

Thanks for your advice on this matter

[BongoBonkers]

Haydn, does the rotor arm pull off or is it secured with a bolt or something? The access is poor as I'm sure you recall and I can't see the top of it easily. Thanks

[haydn callow]

Rota arm is held on by 2 x X head screws.....a bit tricky to get at ..... I used a screwdriver bit....about a inch long....and a spanner to turn the bit......rotate the engine to get each screw into position.....once you have the knack it's easy enough......I replaced the screws with allen head screws so in future it's dead easy.
Don't drop the screws....you will never finf them

Use a mirror to spot the screws

[cheffy34]

After some fun investigative work this evening in the dark wind and rain I was overjoyed to discover that two of the contacts inside the distributor cap are so worn as to be effectively not there! I am very pleased about this and have ordered a new cap and arm from the Bongo shop. I will let the AA man off not clocking this fact when he had the cap off a few weeks ago as he was a really nice bloke and it was also dark windy and raining that night but he didn't have the benefit of a garage to be working inside!

Thanks for pointing out checking the cap Haydn. Although it's kind of obvious I had glossed over it as the AA man had already investigated that area. It just goes to show, until you've seen it with your own eyes you can't 100% rule it out. Cheers

Completely normal for two conatcts to be flush with cap can't remember which ones to be exact, a new one will be the same but new, i now have three caps my old one someone elses old one came free with a dizzy and the new one i put on mine 3 year ago all the same and in good working order after a good cleaning

My other post on your other post makes sense now


WATER INGRESS

Dar

[Ron Miel]

.........This is worse when the engine is cold and gets progressively better as it warms up to the point where it is pretty much cured after 30 minutes or so on the road and then behaves perfectly.

During one very bad incident I parked it up en route and called the AA to look at it...............

Wasn't this a bit contradictory? If it was "pretty much cured" after warming up, why park up and call the AA en route?

A V6, just misfiring on one cylinder, cold or idling feels rough - but once cruising it can be deceptively smooth, despite the now "hidden" misfire. See below.

Of course, if you pull up, and still have a misfire, particularly if on both fuels, it will then be lumpy again until you regain speed.

Hope you've in fact cured the problem now though - but, if not, you might have a similar connector problem to the one I recently described, and refer to below.

.............Our van has LPG but the problem seems the same on gas or petrol.

Has anyone else had a similar problem?.....

Well, yes, I think I have - as reported, and solved, here: http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=53002.

If changing HT leads, dizzy cap, rotor arm, etc, (all things I did first - I even changed an injector on my garage's incorrect diagnosis) hasn't fixed it, I suggest you think about the extra electrical connections, and LPG ECU circuits, inserted as part of the LPG system into each separate petrol injector electrical (pulse) signalling line.

My problem turned out to be a bad connection on one petrol injector signal line, in the multi-way output connector from the petrol injectors side of the LPG ECU - so it only resulted in a petrol misfire. If you've got a similar bad connection, or connections, but in the main ECU inputs to the LPG ECU (i.e., the input side of the LPG ECU - in either its wiring loom or, more likely, again in one of its multi-way plug/socket connectors), you will get misfiring on both petrol and LPG.

When I had a cold start misfire on one petrol injector, of course the engine felt (and was) lumpy, but once warmed up and at cruising speed, the vehicle and flywheel momentum, and the general V6 balance, made it imperceptible except when accelerating - when power was noticeably less than on LPG. In my case, LPG running remained smooth at all times though, as my particular bad connection did not affect LPG injector signalling.

Suggest you try wiggling the cable looms and multi-way connectors on your LPG ECU, if you've still got the problem.

I suspect that a lot of the misfires, lumpiness and so on that get reported on LPG converted Bongos, particularly on petrol, are probably down to all the extra connectors, and often solder-jointed cable looms, in the petrol injector circuits. I'm drafting a suggested update to the members' fact sheet, to highlight this, and will send it to Ian to consider when finished - just waiting on a promised input this week from Paul - lpimports.

[Ron Miel]

Edited to delete (delete option gone), as it was just an unintentional duplicate post, due to to still excruciatingly slow forum responses.

[Ron Miel]

.........This is worse when the engine is cold and gets progressively better as it warms up to the point where it is pretty much cured after 30 minutes or so on the road and then behaves perfectly.

During one very bad incident I parked it up en route and called the AA to look at it...............

Wasn't this a bit contradictory? If it was "pretty much cured" after warming up, why park up and call the AA en route?

A V6, just misfiring on one cylinder, cold or idling feels rough - but once cruising it can be deceptively smooth, despite the now "hidden" misfire. See below.

Of course, if you pull up, and still have a misfire, particularly if on both fuels, it will then be lumpy again until you regain speed.

Hope you've in fact cured the problem now though - but, if not, you might have a similar connector problem to the one I recently described, and refer to below.

.............Our van has LPG but the problem seems the same on gas or petrol.

Has anyone else had a similar problem?.....

Well, yes, I think I have - as reported, and solved, here: http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=53002.
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........I'm drafting a suggested update to the members' fact sheet, to highlight this, and will send it to Ian to consider when finished - just waiting on a promised input this week from Paul - lpimports.

Should have said "...members' LPG fact sheet...", also that, although I think the mulitiple injector (ground) pulsing interconnections are the likely culprit if it's this sort of fault at all, there's also possibility of a fault in either the main engine ECU or the LPG ECU, both of which affect running on both fuels.

The main ECU always works quite normally, with no awareness of the LPG installation, but its injector pulsing signals are intercepted by the LPG ECU, and either switched through unaltered to the petrol injectors, or used to trigger the LPG ECU's separate, internally generated, pulsing outputs to the discrete LPG injectors. Therefore a relevant software glitch or physical electronics failure, in either ECU, could also cause the problem you have. I've sent a PM to Paul/lpgimports, to alert him to this topic, apparently similar to mine, so perhaps he'll comment on that likelihood.

Meanwhile, perhaps before wiggling connections, you could also try ECU resets - disconnect your battery (or batteries), push the brake pedal for 30 seconds to let the stop lights drain down any residual power, then re-connect. Theoretically, you might have to drive a bit for the ECUs to reset their trims but when I did it, there seemed to be little change, to be honest.