Missfire

[Thumpngrunt]

Hi everybody, this is my first post. I'm from Australia where there are not a lot of Ford Explorers these days. Mine is a 2000 UR model with 198,000Km on the clock.
It is a dual fuel conversion, running ULP petrol and injected LP gas (Liquified petroleum gas), and has developed an intermittent missfire both on petrol and LPG.
Initialy it ran fine on petrol, but wouldn't run on LPG, then wouldn't run on petrol either.
OBD11 diagnostic was inconclusive, with no stored codes. Fuel rail pressure was about 20PSI, so I replaced the pump and fuel filte, now running at 60psi.
Still no go, so replaced the crankshaft sensor, and the camshaft sensor.
Ran on petrol then , but not on LPG, but on petrol would struggle at times.
I took it to a local mechanic who is very thorough and fount the LPG computer faulty, replaced it, and got the LPG side of the system working, tested for air leaks with a smoke tester and found some leaks and repaired them, but this misfire on both fuels remains.
He also replaced the sparkplugs which had been reccomended and installed at the LPG conversion, (80,000Km ago).
Any thoughts would be appreciated.

 

[BrooklynBay]

Welcome to this forum! What kind of spark plugs were installed? I once installed Bosch platinum, and had no power, so I removed them, and installed Autolite/Motorcraft iridium which works fine.

 

[amj441]

Hi everybody, this is my first post. I'm from Australia where there are not a lot of Ford Explorers these days. Mine is a 2000 UR model with 198,000Km on the clock.
It is a dual fuel conversion, running ULP petrol and injected LP gas (Liquified petroleum gas), and has developed an intermittent missfire both on petrol and LPG.
Initialy it ran fine on petrol, but wouldn't run on LPG, then wouldn't run on petrol either.
OBD11 diagnostic was inconclusive, with no stored codes. Fuel rail pressure was about 20PSI, so I replaced the pump and fuel filte, now running at 60psi.
Still no go, so replaced the crankshaft sensor, and the camshaft sensor.
Ran on petrol then , but not on LPG, but on petrol would struggle at times.
I took it to a local mechanic who is very thorough and fount the LPG computer faulty, replaced it, and got the LPG side of the system working, tested for air leaks with a smoke tester and found some leaks and repaired them, but this misfire on both fuels remains.
He also replaced the sparkplugs which had been reccomended and installed at the LPG conversion, (80,000Km ago).
Any thoughts would be appreciated.

are there any stored codes? or is it more of a stumble?

 

[J_C]

Hook it up to a scan tool capable of ford specific codes and real time data. See if any of the data looks off including long term fuel trim.

Search youtube for no code misfire and then if you identify the cylinder, check for spark (but it's probably fine to have few enough misfires to not generate a code, except were the wires replaced?), cylinder leak down or compression test, then suspect the fuel injector if everything else checks out. At that point you might try adding techron (or another brand that also has a high % PEA in it) fuel system cleaner to 1/2 tank of gas and run it a while.

 

[Thumpngrunt]

Hook it up to a scan tool capable of ford specific codes and real time data. See if any of the data looks off including long term fuel trim.

Search youtube for no code misfire and then if you identify the cylinder, check for spark (but it's probably fine to have few enough misfires to not generate a code, except were the wires replaced?), cylinder leak down or compression test, then suspect the fuel injector if everything else checks out. At that point you might try adding techron (or another brand that also has a high % PEA in it) fuel system cleaner to 1/2 tank of gas and run it a while.

Thanks for your reply J.C,. To expand on my original post, the missfire is irregular and is common to both fuels used. There are no stored codes, but having said that, communication between the OBD2 scanner is inconsistent. I tried using Forscan but it won't communicate with the CPU either. The problem is strange as the only OBD2 scanner I can get to work (Partially) is an old OBDWhizz, which leaves me using the old fashioned diagnostic, logical analysis. The fact that both petrol and LPG have the same missfire (Erratic) discounts fuel associated issues, although the main computer feeds data to both systems, which in turn is dependant on accurate information from the sensors ( Crank, cam temp').
Add to that the fact the car is twenty five years old, the possibility of poor electrical connections is another consideration. I have worked on a variety of vehicle makes including diesel over my 60 year working life and am continually amazed at the progress made especially with the advent of digital computing. The old days were much simpleer, but the modern auto is in my humble view quite incredible. Cheers

 

[Thumpngrunt]

Welcome to this forum! What kind of spark plugs were installed? I once installed Bosch platinum, and had no power, so I removed them, and installed Autolite/Motorcraft iridium which works fine.

Welcome to this forum! What kind of spark plugs were installed? I once installed Bosch platinum, and had no power, so I removed them, and installed Autolite/Motorcraft iridium which works fine.

Thanks for your reply Brooklyn Bay, I will have to find out from the mechanic where the car is at the moment. I'm 77 years old and have reached the stage in my life where I will only do the simpler straightforward servicing & minor repairs. The mechanic who is pursuing the problem told me that they were what is reccommended for dual fuel with an expected service life of 1000,000Km.
This Explorer is in almost pristine condition and I really like it, so I'm prepared to spend reasonable money on it, but here in Australia, the Explorer is not in high demand and if it reaches that point, I'l regretfully trade it for something in the Ranger or Everest stable. Cheers

 

[410Fortune]

How long ago were the wires replaced? Ignition wires can cause misfires without trouble codes present

You can try watching it run in the dark and see if there is any arching between plug wires and the block

 

[wollimann]

Sometimes ago i had a misfire after changing wires and the OBD Scanner could read
a misfire. So there should be a DTC. In my case some of the new cheap wires were crap.
I recommend using Motorcraft wires.

And for the LPG system the NGK Laser Line 1516 is the best spark in my opinion.
Onother thing could be the LPG evaporator, the LPG is worm up by coolant, if 40°C is reached the LPG computer takes control.
The coolant is seperated by a rubber membrane, which frequently cracks.
So coolant could be burned which could cause a misfire too.
On the other side LPG could get into the coolant, LPG bubbles getting into the coolant reservoir.
If you have a PRINS evaporator older than 5 years i would take a look at it.
This is my third one.

These are the water side issues, but there could be a LPG side issue. Read about bad things, sometimes the plastic air intake
is busted/exploded while both Petrol and LPG was injected at the same time. Big misfire!
So take care of the LPG system, LPG filters must be serviced regularly, no LPG leaks in rubber hoses, loud ticking of LPG injectors
will annouce the end of life span.

regards to the outback!

 

[C420sailor]

Some PCMs have a misfire monitor, some don’t. The ones that do constantly monitor crank position rate…a dropping cylinder will result in a decrease in crank angular velocity at a particular point in crank rotation. Thats how it detects it. As the crank rotates, its rate is constantly fluctuating as each cylinder fires. When one doesn’t, that predictable pattern is interrupted.

Forscan allows you to pull this data, but only if the PCM supports it.

 

[Thumpngrunt]

Some PCMs have a misfire monitor, some don’t. The ones that do constantly monitor crank position rate…a dropping cylinder will result in a decrease in crank angular velocity at a particular point in crank rotation. Thats how it detects it. As the crank rotates, its rate is constantly fluctuating as each cylinder fires. When one doesn’t, that predictable pattern is interrupted.

Forscan allows you to pull this data, but only if the PCM supports it.

Thanks for your thoughts C42sailor, the latest that mechanic has found is the sounf of an airleak on the RHD at the rear of the motor. Difficult to lacate and the usual trick of spraying combustible liquid like brake cleaner in the area shows a positive respnse sometimes, but not always.. There are seals on the upper and lower part of the plastic manifold that have hardened over tim, and these may be part of the problem, especialy the ones contacting the head, which much hotter. These are not readily available in Australia, so may require importing from the states. Overall, there is a sense of moving forward, and I will keep updating .

 

[Thumpngrunt]

Sometimes ago i had a misfire after changing wires and the OBD Scanner could read
a misfire. So there should be a DTC. In my case some of the new cheap wires were crap.
I recommend using Motorcraft wires.

And for the LPG system the NGK Laser Line 1516 is the best spark in my opinion.
Onother thing could be the LPG evaporator, the LPG is worm up by coolant, if 40°C is reached the LPG computer takes control.
The coolant is seperated by a rubber membrane, which frequently cracks.
So coolant could be burned which could cause a misfire too.
On the other side LPG could get into the coolant, LPG bubbles getting into the coolant reservoir.
If you have a PRINS evaporator older than 5 years i would take a look at it.
This is my third one.
View attachment 465382

These are the water side issues, but there could be a LPG side issue. Read about bad things, sometimes the plastic air intake
is busted/exploded while both Petrol and LPG was injected at the same time. Big misfire!
So take care of the LPG system, LPG filters must be serviced regularly, no LPG leaks in rubber hoses, loud ticking of LPG injectors
will annouce the end of life span.

regards to the outback!

Sometimes ago i had a misfire after changing wires and the OBD Scanner could read
a misfire. So there should be a DTC. In my case some of the new cheap wires were crap.
I recommend using Motorcraft wires.

And for the LPG system the NGK Laser Line 1516 is the best spark in my opinion.
Onother thing could be the LPG evaporator, the LPG is worm up by coolant, if 40°C is reached the LPG computer takes control.
The coolant is seperated by a rubber membrane, which frequently cracks.
So coolant could be burned which could cause a misfire too.
On the other side LPG could get into the coolant, LPG bubbles getting into the coolant reservoir.
If you have a PRINS evaporator older than 5 years i would take a look at it.
This is my third one.
View attachment 465382

These are the water side issues, but there could be a LPG side issue. Read about bad things, sometimes the plastic air intake
is busted/exploded while both Petrol and LPG was injected at the same time. Big misfire!
So take care of the LPG system, LPG filters must be serviced regularly, no LPG leaks in rubber hoses, loud ticking of LPG injectors
will annouce the end of life span.

regards to the outback!

Sometimes ago i had a misfire after changing wires and the OBD Scanner could read
a misfire. So there should be a DTC. In my case some of the new cheap wires were crap.
I recommend using Motorcraft wires.

And for the LPG system the NGK Laser Line 1516 is the best spark in my opinion.
Onother thing could be the LPG evaporator, the LPG is worm up by coolant, if 40°C is reached the LPG computer takes control.
The coolant is seperated by a rubber membrane, which frequently cracks.
So coolant could be burned which could cause a misfire too.
On the other side LPG could get into the coolant, LPG bubbles getting into the coolant reservoir.
If you have a PRINS evaporator older than 5 years i would take a look at it.
This is my third one.
View attachment 465382

These are the water side issues, but there could be a LPG side issue. Read about bad things, sometimes the plastic air intake
is busted/exploded while both Petrol and LPG was injected at the same time. Big misfire!
So take care of the LPG system, LPG filters must be serviced regularly, no LPG leaks in rubber hoses, loud ticking of LPG injectors
will annouce the end of life span.

regards to the outback!

Thanks Wolliman, in my reply to C42sailor, the latest that mechanic has found is the sounf of an airleak on the RHS at the rear of the motor. Difficult to lacate and the usual trick of spraying combustible liquid like brake cleaner in the area shows a positive respnse sometimes, but not always.. There are seals on the upper and lower part of the plastic manifold that have hardened over tim, and these may be part of the problem, especialy the ones contacting the head, which is a much hotter environment. These are not readily available in Australia, so may require importing from the states. Overall, there is a sense of moving forward, and I will keep updating .

 

[C420sailor]

Those shrink and harden over time…and somewhat quickly too.

If you can’t find replacements, perhaps try soaking them in a seal conditioner to plump them up. A thin coating of the appropriate fuel /oil resistant RTV may help too.

Obviously new seals is best

Can you see the PCV and tubing? If that disconnects or cracks it’ll make a helluva leak back there