Misfiring on LPG and Petrol

[Simon Jones]

We had a problem on a mk4 Golf where a coil pack failed so it was running on 3 cylinders. This triggered an emissions warning light because unburnt fuel was getting into the catalytic convertor which causes it to play up. Fortunately, once coil pack was replaced the light went out, but I have a feeling if left with excess petrol going thru the cat, it will cause premature failure.

How long was it misfiring for? It may be that if you take it out for a good run, the fuel will burn off and the problem may go away.

Mike, some V6 have the extra sensor on the cat but it sounds as if yours is same as mine without one.

[Jim the Box]

Ok took out another run, only 2 miles but enough for the LPG to come on, one thing I noticed when I took my foot off the accelerator the van seemed to maintain speed and revs, also when first started the engine stalled every time I touched the brakes when in drive mode, on returning from my 2 mile run I braked at the junction and reves dropped to around 700rpm, light is still on, have booked it in to a local garage with some knowledge of bongo's, earliest I can get booked in is Thursday. Warning light is still on, although the engine seems fine something is not right (warning light on and the stalling problems).
Thanks for your help so far I will post of any progress, may give it a longer run myself tomorrow to see if I can burn off poss fuel deposit in the cat.

Many thanks jim....

[Jim the Box]

Forgot to mention Simon, it was originally misfiring for about 40 miles(which was my first post) but not for the whole journey only when accelerating or when asked to climb a hill, the HEAT warning light never appeared until I took it for a 2 mile run after changing the leads, and found I had reversed 2 of the leads due the supplier identifying the cables incorrectly. Have started it several times and given it a couple of 2 mile runs, the warning light is still on, and I have this engine stalling problem when cold, even putting it in drive with the handbrake on is an issue. Hoping to go to Silverdale bash on 17th so need to cure this soon and then have a few drives about in it to be confident it is ok before making a long trip.
New spark plugs come tomorrow.
If no success may change the coil next if the garage can't cure the sensor problem.
Also page 170 and 156 in the service manual mention symptoms for the heat warning light and possible issues I may be having.

[the laird]

Jim my gutt feeling is it may be a distributor fault ,hope it's not but a diagnostic check is a must or you could be throwing money at it

[Jim the Box]

Actually thinking of doing just that Gordon, I assume all my kit is 18 yrs old, have already replaced the leads, new iridium plugs come tomorrow, so may just go for distributor cap, rotor arm and a new coil as well. Garage at eastlinton Is checking out my sensors cylinder balance etc on Thursday if plugs don't improve matters.

[mikeWalsall]

Oh ... I assumed you had replace the rotor and dizzy cap when you did the leads ..

The rotor is a bit weird in that the tip as a rough / sandpaper look / feel to it .. I dunno why ..



Also when refitting ... double check that the carbon brush is still located in the middle of the Dizzy cap ..



... and the large 'O' ring is in good nick .. I put a smear of Vaseline round it ..

[Jim the Box]

When I saw the cost of all the genuine mazda parts Mike, I decided to change plugs and leads first. I do plan to replace them all in time as, I am replacing parts that are 18years old, but felt well in excess of £400 in one go was a lot of money, was'nt even sure if it was bad fuel or a sensor problem or a loose connection somewhere, plugs and leads fitted, running fine but I need to put in garage to clear the "heat" fault warning light and get spark/ cylinder balance check. It was an intermittent fault to start with so don,t know if it's cleared for good need to give it a few good runs.

[mikeWalsall]

I agree with your price comments .. A 'normal' Ford .. Vauxhall .. Honda etc: V6 cap maybe £15ish .. Mazda .. £??

I changed all mine at the same time as .. excluding the 'guaranteed for life' after market leads .. I managed to source all OEM parts of eBay at a good price ..

If the dizzy was not in such an awkward spot it may have been OK with a clean up of the terminals / rotor and a check on the carbon pick up .. but I did not fancy the hassle of removing it and then finding something 'un fixable' .. burnt out / arcing or what ever ..

I use iridium plugs in my Toyota as every four years the floor as to come up to change them .. but as the Bongos are so easy to get to .. I fit normal (cheap) OEM specified NGK each year when I change the oil / filters etc ..

[Jim the Box]

After fitting new HT leads and plugs took the bongo to the garage for a check over, where we were given a clean bill of health. Balance test on cylinders etc. the heat fault light would not clear by itself garage cleared it by some method where the battery was disconnected for a few minutes and a reconnection procedure which then cleared the fault. Took her on a 50mile run today everything is fine, think I will still purchase the dizzy cap rotor arm and coil though. Many thanks to all who posted with advice and great pictures.

Jim.......