Hi Everyone,

Car – 92 Verada Wagon 3.0L V6 SOHC (Auto).

This problem has been posted before, but I can’t find a solution, & there’s a critical difference to most people’s misfire... I run dual fuel so we can eliminate any petrol system issues, like pump, filters, injectors etc.

It seems to misfire randomly, mostly when it’s at full temp, even more on hot days. But occasionally when cold &/or idling too. Being under heavy load, e.g. accelerating, towing, &/or aircon make it less random & more consistent. It mostly happens between 2000-4000RPM. In its very worst state, it won’t even rev past about 4000RPM even in neutral (this only on petrol though), It seems to go into a full rev-limiting mode. It's certainly degrading to the performance & economy. I suspect the lurching it produces is not good for the transmission either.

The car’s 17+yo now & has 250,000 on the clock, so it’s needing work as it does blow smoke. I know the valve stem seals need work, valves & rings probably need a going over too. In reality the heads need a full work over.

What I have tried & results...

HT leads – small difference (changed from Bosch to Eagle)
Distributor cap – small difference
Rotor button (notched to solid) – reasonable difference
Spark plugs – small difference (changed from Bosch to NGK lower temp & 1.1mm gap)
Timing – small difference
(all the above items are general maintenance items anyway, so as expected, they would exaggerate existing problems)

Coil, Distributor, Running on Petrol or Gas, Transmission service (basic fluid & filter) & Engine service (basic oil & filter) – all produced no notable difference

Engine fault codes – 41 (due to injectors cut off while LPG is on) which is expected & ok.

So we know it’s heat related, & I suspect it’s spark related too, as it happens when the spark should be at its biggest. Leaky valves could be affecting it. I had suspicions it could be Transmission related, but I’m not so sure now, especially as manuals can have the same issue. Maybe the ECU is having issues? Does anyone know if this vintage of ECU suffers from leaky capacitors? (Confirmed leaking cap's, but not the problem) Maybe the trans is getting hot & the ECU is throttling the power back, but this isn’t consistent with all my findings. Like most people, I change something & the problem seems to go away, then after a couple of days it returns.

Replies & ideas are welcome, as this seems to be a common problem without a common solution so far.

Have you had the converter checked & what type of gas system is it ie Injected or mixer type ?
Have you had the gas strainer / filter changed ?
Have you tried another distributor assembly?
Where abouts in VIC are you?

Yes all those things have been checked or are not related. I had the symptoms before I installed the gas system (mixer type FYI), and it's virtually the same on gas or petrol. I live in Dandenong.

Mmm,
maybe time to open up the ECU and check for leaky capacitors

Edit: ignition coil already checked!

If you are in Victoria, swing by Mal's and get him to take a look. Hot misfires can have lots of different causes.
My misfire was due to a sticking PCV valve and blocked tubing between the rocker covers and the intake manifold.

my old 2g used to do this, we done all of what you did, the biggest thing that helped was we got the injectors cleaned. it sill done it but only every now and again

perry - good thoughts, except the fact that it happens on both petrol and LPG in my case means that the injectors cannot be to blame. I can be sure of this because the injectors aren't used while running on LPG.

MarkH - Magna Driver came by this arvo and pretty much confirmed everything I already know, I've PM'd MadMagna on his advice and will see where I can get with him. There's a couple of modules that would be worth swapping with known good ones, including the ECU and Trans Computer (TCU???) that may be having "issues" such as leaky SM Cap's. The symptoms are somewhat consistent with that possibility and the production date is of the era of those caps going faulty due to leakage.

Edit - ECU removed & found C104 has leaked. It's also damaged C6 in the process. They're simple power supply bypass cap's, so I replaced the faulty components - however the problem still exists... back to the drawing board.

By the way, next time you're in that area of your car, it may be worth checking the ECU for leaky caps. It'll usually look like a burnt section on the board around them.

Just to replay my initial findings... Swapping the Distributor or Coil, or doing Engine Service, Trans service or ECU Reset have NOT produced any result at all. General "service items" such as Plugs, Leads, Dizzy Cap and Rotor Button have all seemed to make SOME difference, but only short lived. A day or so later and the problem has returned. My next step is to open up the ECU to have a poke around and see if it's sick.

I'm pretty 'over' fixing this car, or any car for that matter. But I need to keep this one for at least 12 more months to make sure the LPG system pays itself off. Would be nice to have it for another few years though, as it's nice to drive (usually).

Did you pull the PCV out and check it's not stuck ? As with medicine, the patient may have more than 1 problem.

MarkH - I haven't pulled the valve out, however it does appear to be working fine. There's decent vacuum from it and a solid click when covered, indicating it's got free movement inside. I'm sure there's more than one problem here, but I'm pretty sure there's only one thing causing this weird misfire issue.

Keep the ideas coming, we'll work it out eventually.

I have a 93 v6 with similar symptoms to the above and I have done similar repairs, including reco injectors ,all to no avail. On this site I found out how to extract fault codes from the car and came up with 11, 12 which are oxygen sensor and airflow sensor( someone correct me if wrong) A search on Wiki says O2 sensors are critical, so am buying O2 sensor this week.

rex2ce - If you've EVER had the sensors that correspond to the fault codes unplugged while the ignition is on, it will log the code and stay there until it's either reset or cleared. And yes the fault codes you've listed are correct. Could be worth a reset before you go purchase the new parts, the see if the fault codes reappear.

In my particular circumstance, neither of these fault codes come up.

Thanks fluap, but I have reset them by disconnecting the battery for a short while. First time you start the engine after reset, no "check engine light" appears, but subsequent starts the CEL glows for about 15 secs and the codes can be extracted again 11, 12.

Seems like we're all following the correct procedures then. No need for flow charts here ;)

Oxygen sensor changed, motor still missing. H.O.S.

Oxygen sensor changed, motor still missing. H.O.S.

Yep it's a weird one that's for sure! I'm a bit broke right now, so when I have some more cash I'll delve into swapping parts again to try find the problem. I spoke to Mal too, he only had checking the compression to the list of things to do, so that will follow sometime soon. But I'll live with the issue for now.

Good luck to us all.

Solved the problem today! I read on the net last night that on cars equipped with Mass Air Sensors, any leak downstream of the mas will cause symptoms like my car had. I remembered seeing red silastic type stuff on the throttle body flange when I dismantled same to remove injectors. A check inside the intake tube where it fits over this flange showed it to be hardened from age/use. Cleaned both surfaces up with prepsol, applied some 3T sealant, fitted together and tightened, left for an hour to cure . Drove car to work this arvo, plenty of power , no missing, was even able to use A/C. Great cars these Magna's LOL

Solved the problem today! I read on the net last night that on cars equipped with Mass Air Sensors, any leak downstream of the mas will cause symptoms like my car had. I remembered seeing red silastic type stuff on the throttle body flange when I dismantled same to remove injectors. A check inside the intake tube where it fits over this flange showed it to be hardened from age/use. Cleaned both surfaces up with prepsol, applied some 3T sealant, fitted together and tightened, left for an hour to cure . Drove car to work this arvo, plenty of power , no missing, was even able to use A/C. Great cars these Magna's LOL

That's great news! I'll take a look too, but I don't think it's the cause of mine. Can you check back in about a week and confirm if yours is still working fine please? As most people seem to "fix" the problem then find it's back within a few days.

Ok today I've delved back into this problem again (after having some time off due to frustration). I had to replace the ISC due to it being faulty, however that wasn't the cause of this issue.

What has seemed to work so far, is replacing the Distributor Cap. It's the only thing I haven't replaced in the ignition system until now (so it makes sense). My previous Dizzy Cap looked fine, nothing broken, clean etc etc. But perhaps somewhere there was some sort of issue. I did read that Repco had a bad batch of these at one stage, and I think that's where I purchased it from a couple of years back. The new one was purchased from Autobarn after much searching for a decent price, $53 in the end. Everyone else was between $75 and $100+... crazy prices!!!!

So I'm tentatively saying the ignition system has been the problem all along, with the Dizzy Cap being the major contributor. However the Plugs, Leads, Cap, Rotor Button, Distributor and Coil have all now been replaced, so any of those could have been a problem too.

I'll update this thread again if the issue returns, as it has in previous times.

If the problem comes back try gapping your plugs a tad closer, it sounds like an ignition problem, with something breaking down under load. Check/clean the plug on the distributor, ignition coil and all the others in the ignition system, and run a multimeter over all your plug leads, even though they are new, and also the ignition coil to distributor HT lead. Swap out the power transistor to rule that out.

Try gapping your plugs a tad closer, it sounds like an ignition problem, with something breaking down under load. Check/clean the plug on the distributor, ignition coil and all the others in the ignition system, and run a multimeter over all your plug leads, even though they are new, and also the ignition coil to distributor HT lead. Swap out the power transistor to rule that out.

The problem is actually solved. But all those mentioned items had been checked or replaced in some way already. The Dizzy Cap seems to have made the primary difference. Not a hint of any 'missing' so far. Fingers crossed it stays that way.

The problem hasn't shown it's ugly face again, so it looks like the Dizzy Cap was the fix. If only I'd tried that nearly 2 years ago when it started happening!!! Sheesh. At that time, the cap was only a few months old too.

Ok
What has seemed to work so far, is replacing the Distributor Cap. It's the only thing I haven't replaced in the ignition system until now (so it makes sense). My previous Dizzy Cap looked fine, nothing broken, clean etc etc. But perhaps somewhere there was some sort of issue. I did read that Repco had a bad batch of these at one stage, and I think that's where I purchased it from a couple of years back. The new one was purchased from Autobarn after much searching for a decent price, $53 in the end. Everyone else was between $75 and $100+... crazy prices!!!! .

Crazy prices or not, dizzy caps should always be replaced with genuine, this is not an old EK Holden you're running here, Electronic ignitions require high density caps, not ones made from Bakelite, no matter what an Autofart or Rip Every Poor ******* Off (Repco) anything you buy from these elcheapo stores will fail long before the original does, electronic ignitions demand high end dizzy caps.

It never pays to be cheap with your car, when I was in business if a customer didn't like my quote and tried to barter me down I would simply refuse, they pay for genuine or better or bugger off and when you consider that ALL my customers got a copy of the original receipts and my labour costs, all tax delectable they had no reason to complain.

With your particular problem I was of the thought it may have been the centrifugal weights in the dizzy, but it would appear I was on the wrong track there, good for you for nutting it out, process of elimination can be a pain.

Well done. kik

Crazy prices or not, dizzy caps should always be replaced with genuine, this is not an old EK Holden you're running here, Electronic ignitions require high density caps, not ones made from Bakelite, no matter what an Autofart or Rip Every Poor ******* Off (Repco) anything you buy from these elcheapo stores will fail long before the original does, electronic ignitions demand high end dizzy caps.

It never pays to be cheap with your car, when I was in business if a customer didn't like my quote and tried to barter me down I would simply refuse, they pay for genuine or better or bugger off and when you consider that ALL my customers got a copy of the original receipts and my labour costs, all tax delectable they had no reason to complain.

With your particular problem I was of the thought it may have been the centrifugal weights in the dizzy, but it would appear I was on the wrong track there, good for you for nutting it out, process of elimination can be a pain.

Well done. kik

Yes it was a pain, a huge one that lasted close to 2 years in all. But on the genuine v's aftermarket topic, I didn't even check Mitsubishi for the price. Oddly I didn't even think of them, probably because prices I've been quoted before have been astronomical, so it's turned me off. What we should be aware of, is the quality and spec's (if available) of aftermarket v's genuine parts. Sometimes aftermarket are better, sometimes worse, and sometimes they're identical parts out of the same factory that are differently branded. If the cap I bought was a bakelite version, I wouldn't have bought it. IMO it's probably identical to the original item. I think I must have had bad luck with the previous one that failed within a few months (albeit without me knowing that was the culprit).

So I say if people spend $1000 on servicing a vehicle with genuine parts, then that's their choice. But most of us are very comfortable spending half the parts cost to save a few dollars. That's especially true with a car that's 18yo and only worth about $3k.

The problem isn't only in cost, it is to do with spotting quality for crap.
Now I know we all can't get parts at discount prices (benefit of being a mechanic), but we can get quality at reasonable prices that will out last
the cheaper stuff by 4 X at least.

A few years back I rang Rex Gorrell in Geelong for a water pump for a 4Y engine in a Hiace, what I was given was a Taiwanese import, and this was
from the dealer, I did not order after market, never ever do, I was charged full price for a genuine part and they had sourced me a non gen, my wife
picked the parts up as she always used to, and I hit the roof when I saw the part, turns out they were out of stock of genuine so sauced from a cheaper
supplier and charged me full rate, minus trade discount, needless to say I got it sorted, but had I not been aware it could well have ruined the engine entirely.

After market water pumps are a joke, wrong pitch impellers, wrong casting, poor impeller shafts, poor bearings etc, they cause cavitation, corrosion and shear
clean off at any given speed, I have known a customer fit one that snapped off at just above idle as she was backing out her drive.

Some items we all pay the same for no matter what, but these are items that are (or at least should be) changed at each service, such as oil filter, oil etc.

Doing your own service compare all items before purchase for price V's durability, such as.

Leads, let's say Top guns, yes crap but a popular choice average 6 cyl price $60.00, now compare that to custom made 10MM NASCAR leads $88.00 and last
10 years not two years, you see where I am going with this?.
Dizzy caps, elcheapo maybe $50 to $60 last 1 month to two years max, genuine 5 to 10 years $90.00.
Plugs NGK no matter what, don't touch Champion, Bosch are good also.
Engine coolant $30 Autofart, $15 Kmart and Kmart's is far far better.
Oils Synthetics all the way, no prehistoric sludge left after changes, last's twice as long. (however I recommend regular oil change 10 to 15,000 ks)
Kmart brand oils, or blue label stuff is simply recycled and offer limited lubricant quality.

Brake pads, using non gen is no issue here, but for long haul vehicles with little stop go fairly cheap Bendix are great, stop start traffic use cab pads,
they last years, but do cause wear to rotors, however rotors for the most part are cheap anyway.

Basically all I am trying to get across here is that indeed at the time of purchase items may seem expensive, but in the long haul will save you money
time and just maybe your car, not to mention your or somebody Else's life.

Just do a little research before you buy. Be safe out there. kik

Kik -

All valid points of course, and obviously ones from experience so that's great. However it appears that you're very much biased against certain brands/products.

The replacement water pump you got and returned, may well have worked just fine and lasted for many years, but you can't be sure because you didn't actually try it. So in fact it 'MAY" have been inferior, but we'll never really know. And the one that had snapped just above idle speed, well that was obviously a faulty, damaged or incorrect product, I'm pretty sure another one of the same brand wouldn't have done the same thing, or they'd all have to be recalled.

You also say Bendix pads are only good in certain usage scenarios, but Bendix do at least 3 grades of commonly available pads (last time I checked), which all have their designed applications. As you say, some different types may stop you better, but the rotor's wear faster, this is an unavoidable tradeoff that's not brand dependent.

It seems you have something against Autobarn and Repco, possibly some other parts sellers too. It may be wise to remind yourself that most of these places don't actually manufacture their own parts, they simply resell them under their own banner. The faulty batch of Dizzy Cap's that I mentioned from Repco, was actually recalled when it was realized, people were offered replacements etc etc. So the company had done the right thing by everyone.

Also worth noting, was that the prices I was quoted ($57 - over $100) for the Dizzy Cap on my car, were all for the exact same brand. So in my case it was simply a case of who had stock, and who had it cheapest. Yes it's probably an aftermarket one, but it works fine. If it fails in the future I'll deal with it then. If it fails in an unusually short period of time (which my last one unknowingly did), I'll look at a warranty claim (my own negligence made it not possible this time). Some people won't care if it lasts 2 or 10 years. If they only intend to keep the car for another year or so, like many cars this age, then it's somewhat irrelevant.

But anyway this is waaaay off topic. Basically I had misfiring issues like some others had, and eventually found the cause of mine. So it was to impart the knowledge I'd gained during my ordeal so others may perhaps solve their issues too. Which in a roundabout way, repays the help the forum has given me in solving it.

Thanks AMC :)

Arching leads and distributor caps often show up at night if you lift the bonnet with the engine running.

Kik -

All valid points of course, and obviously ones from experience so that's great. However it appears that you're very much biased against certain brands/products.

Yes I am.


The replacement water pump you got and returned, may well have worked just fine and lasted for many years, but you can't be sure because you didn't actually try it. So in fact it 'MAY" have been inferior, but we'll never really know. And the one that had snapped just above idle speed, well that was obviously a faulty, damaged or incorrect product, I'm pretty sure another one of the same brand wouldn't have done the same thing, or they'd all have to be recalled.

You know that's a fine opinion to have, but this was a customers car, not yours and not your choice to fit it, if you had seen the damage after market pumps do then there would be no questions about whether it should have been fitted or not.


You also say Bendix pads are only good in certain usage scenarios, but Bendix do at least 3 grades of commonly available pads (last time I checked), which all have their designed applications. As you say, some different types may stop you better, but the rotor's wear faster, this is an unavoidable trade off that's not brand dependent.

I never said anything of the type of any one thing being brand dependent, fact remains Bendix are the most popular that's why I chose that brand, and you basically repeated what I said anyway.


It seems you have something against Autobarn and Repco, possibly some other parts sellers too. It may be wise to remind yourself that most of these places don't actually manufacture their own parts, they simply resell them under their own banner. The faulty batch of Dizzy Cap's that I mentioned from Repco, was actually recalled when it was realized, people were offered replacements etc etc. So the company had done the right thing by everyone.

I needn't remind myself of anything, there are plenty of Mum and Pop stores that supply higher quality parts at reasonable rates and you get personal service, not supermarket checkouts, and Repco are and always have been the dearest of the bunch, how they manage to survive is beyond my comprehension.


Also worth noting, was that the prices I was quoted ($57 - over $100) for the Dizzy Cap on my car, were all for the exact same brand. So in my case it was simply a case of who had stock, and who had it cheapest. Yes it's probably an aftermarket one, but it works fine. If it fails in the future I'll deal with it then. If it fails in an unusually short period of time (which my last one unknowingly did), I'll look at a warranty claim (my own negligence made it not possible this time). Some people won't care if it lasts 2 or 10 years. If they only intend to keep the car for another year or so, like many cars this age, then it's somewhat irrelevant.

How is making your car more reliable irrelevant?, you spent $57.00 twice = $114.00 when compared to genuine $90.00, after market water pumps for Magna 4 cyl's are $60.00 and you only get the impeller half of the pump, a genuine one is $55.00 complete, so how is that in anyway beneficial to anyone?.


But anyway this is waaaay off topic. Basically I had misfiring issues like some others had, and eventually found the cause of mine. So it was to impart the knowledge I'd gained during my ordeal so others may perhaps solve their issues too. Which in a roundabout way, repays the help the forum has given me in solving it.

And me passing on my experience to not only you but the rest of the forum differs how?, I don't care whether people take my advice or not, at the end of the day I can't make peoples choices for them, I can only offer experienced advice, the rest is up to the individual. kik

Thanks AMC :)[/QUOTE]

The problem (of variable parts quality) isn't with Autobarn or Repco or anyone else in Australia. A lot of parts for older cars are made by small factories in China that specialise in doing small production runs (min 300) of any part you want to order. Some of these use proper engineering and metallurgy to make a product very close in quality to the original, others take shortcuts or have production problems. These parts are landed in Australia at ridiculously low prices, but are sold at near original prices, meaning a massive profit margin for the importers, but the importers don't know if they got a good batch or not until they get feedback from the "in the field" users, ie the customers. If you want quality guaranteed, look for "Made in Japan" on the box or buy originals from Mitsu dealers. Reject any parts that say "Made in China" from a dealer, and check any rubber/plastic components you buy from a dealer, as they can perish in storage. (eg from personal experience, CV boot rubbers). If you see "Made in China" on anything you buy ask about a warranty and if any customers have returned the item.

Brand names mean very little in China, usually the copies/short product runs will include the original manufacturer's logos and be indistinguishable from the original.

To us this may all seem unreasonable, but the Chinese attitude is to do and say anything to make money. It's part of their culture.

The problem (of variable parts quality) isn't with Autobarn or Repco or anyone else in Australia. A lot of parts for older cars are made by small factories in China that specialise in doing small production runs (min 300) of any part you want to order. Some of these use proper engineering and metallurgy to make a product very close in quality to the original, others take shortcuts. These parts are landed in Australia at ridiculously low prices, but are sold at near original prices, meaning a massive profit margin for the importers, but the importers don't know if they got a good batch or not until they get feedback from the "in the field" users, ie the customers. If you want quality guaranteed, look for "Made in Japan" on the box or buy originals from Mitsu dealers. Reject any parts that say "Made in China" from a dealer, and check any rubber/plastic components you buy from a dealer, as they can perish in storage. (eg from personal experience, CV boot rubbers)

Brand names mean very little in China, usually the copies/short product runs will include the original manufacturer's logos and be indistinguishable from the original.

Dead right, trusting other then original is very hard to do.
One other thing that needs to be taken into account is that making a perfect copy is illegal (copyright infringement)
hence different impellers or castings, and this goes for almost every aspect of a vehicle, including the composition of the materials in which they are made, they only way to not buy genuine is to buy better PERIOD!.