Thursday, December 12, 2013 - 10:39 am, by: John Stafford(Johng12)
I feel like a a donkey right now. I was swapping the driver's side coil as a long shot from John Street and discovered that I had left the IAC plug off so that solves the cyclic revving but still leaves the dying miss on full load and full throttle on both LPG and petrol.
Having replaced the knock sensors there are no sensors left to replace or check for spec. All plugs, leads, coils, ignitors, ecu, karmen vortex have been either replaced with new ones or swapped out from my 32.
I did a temp test on the cats and the passenger's side one was the same temp at the back as at the front so that is looking like the problem and will therefore be my next job.
Thursday, December 12, 2013 - 05:05 pm, by: Dave Rose(Sand_groper)
Is there anything left ?? I know you have done all the electrics ,if i had just read the symptoms in this post #5 i would say something is breaking down cant see how after all that you have done!!! but you could try running the engine in a pitch black garage get some one to stab gas pedal just to see if there is any blue glow or tracking on the engine ,also make sure you have a good engine earth (run a battery jump lead from engine to a good earth ) This is grabbing at straws i know , but this is the level its come too .
John Stafford DieHard Qld. Soarer UZZ31 GT-L V8 and a UZZ32 # 514
Thursday, December 12, 2013 - 08:44 pm, by: John Stafford(Johng12)
Can someone explain how the earth might be an issue when the miss happens regardless of revs or engine movement eg when revving without load and the engine moves, there is no issue at all at any revs and regardless of how sudden you hit the throttle? There are never any starting issues and perfect charge and holding of charge in the battery.
The arching light, glow in the dark, could be worth a try with the covers off, I suppose. My LPG stuff and PCV filter arrangement makes things pretty cluttered, not nice and open as on a normal 31, so getting the covers off is a bit of an ordeal on its own.
Lets see how the cats issue goes when I get to it first.
Friday, December 13, 2013 - 10:54 am, by: Dave Rose(Sand_groper)
If an engine has a bad earth it will use other ways out, feeding through other wires, even coolant ,this is how rads that have been earthed in some way corrode in weeks.There are lots of eddy currants moving over the engine will its running ,the last GTR Skyline we had in the car yard every plug had a separate earth clipped to it. As i say it takes seconds to clip on a battery earth cable and take it for a run , ITS NOT HARD
John Stafford DieHard Qld. Soarer UZZ31 GT-L V8 and a UZZ32 # 514
Friday, December 13, 2013 - 12:02 pm, by: John Stafford(Johng12)
Dave, Does it matter how big the earth is? I have just run an insulated wire that is about 3 mil copper from the battery earth to the body where the battery clamp bolts to the body near the radiator. Does it need to be bigger than this?
I will take it for a run later, tied up for a few hours.
Friday, December 13, 2013 - 02:33 pm, by: Dave Rose(Sand_groper)
As Tom says engine to chassis, best to use a battery jump lead , it probable is not the problem ,but it eliminates it!!!and we are clutching at straws . even a slightly magnetized crankshaft becomes a generator be it only a few volts ,
John Stafford DieHard Qld. Soarer UZZ31 GT-L V8 and a UZZ32 # 514
Saturday, December 14, 2013 - 08:11 am, by: Tom Richards(Tomr)
i would have thought cat problems would have thrown up an error, and the cat glows red hot.
John, can you go back to how/when did the problem 1st appear and what work you had carried out prior to it happening? have we all overlooked something very basic.(fuel, air, spark)Is it possible with all the variables that both your ECU's work ok in the 32, but not in the 31? Can you borrow another ecu?
John Stafford DieHard Qld. Soarer UZZ31 GT-L V8 and a UZZ32 # 514
Saturday, December 14, 2013 - 10:29 am, by: John Stafford(Johng12)
yes Dave,only one TPS as the car does not have traction control.
Hi Tom, I will try and give you history as best as I can. When I first had the LPG fitted it used more than I expected and so I had the installer lean it down but there was then no power. I then discovered that by putting more LPG in car was more powerful than with petrol but the power came in, in waves with LPG, rather than just one constant push when it is on petrol. This is because you can't tune the standard ECU but you can the LPG ECU. I tried to get the LPG power more constant and spent a lot of time adjusting the pressure, the jet sizes and flow of the LPG to get both good economy and great performance and have learned quite a bit about how to get the best out of the vapour injection without having a dyno.
Well, after a very quick run up a mountain road I developed a miss when pulling about 5000 revs, it was like a surge over and over again. I did not suspect the plugs which were 4 electrode Iridium/platinum Bosch and only had about 15000 klms on them, so I set about to change the plug leads, rotors, distributor caps and coils but the miss/die and surge continued. Eventually I decided to put the set of standard copper electrode plugs in and voila, it was back to normal.
But the power still came in like a spooling turbo under full load and full throttle.
So, I put silver plugs in and it was great to about 10,000 kilos but then it seemed to be getting worse regardless of what I did with the LPG map. I thought it must be the plugs again so I changed them out but no better. Then I noticed that it was dying on Petrol too under full throttle. I bought a AFR gauge and its accompanying O2 sensor to see what my tune was doing but it was fine.
Since then I have put a new set of NGK copper core plugs in and rechecked the leads for the right resistance, and done all the things that you know that I have done according to these over 100 posts (Wow, that must nearly be a record I think)and still my patience is holding out. I will win over this
Ok, I think that is as much history as I can remember but concerning the cats glowing red hot and sending up an error code, that depends on if they get too hot but this miss happens even before the oil would be fully hot. I don't flatten it before water temp is up though.
The code is linked to the rear sensor, behind the cat, on these early 91's and only comes on when the cat is glowing as you say, not like OBD2, which actually tells you if the cat has failed, as far as I know?
I think the only way I can really know is to take the cat off and look inside of it and see how water flows through it?
I have the alternator working on the 32 this morning so after I give myself some space to be sure all is perfect on that I can get those cats off. The left hand cat is not getting too hot as far as I can see but it is the same temp at the back as at the front and that means it is not good as far as I can see from Utube videos.
Given a good fresh look at the history the idea of a cat getting worse and worse over time is looking more feasible, what do you think?
I will try that jumper lead from the block to the chassis today to be sure that it is not an earth problem.
Saturday, December 14, 2013 - 11:19 am, by: John Stafford(Johng12)
Here goes for some info on my LPG vapour injection system. It has Hana stainless injectors. BRG Genius Max reducer (rated at about 400 hp). Stag 8 ISA2 computer.
Vapour injection LPG has its own lines/tubes that feed the LPG into the inlet manifold. These lines connect to nipples that are drilled and tapped into the manifold about 25 mils in from the Petrol injectors. The LPG goes in as a vapour via an LPG specific injector. There are different kinds of injectors, 2 specific types. The common type is a simple brass solenoid that opens to allow the LPG in from the "reducer", which is what converts the liquid to a gas by heating it with the heat of the engine coolant, which flows around the water jacket of the reducer. It has a diaphragm in it and this allows you to adjust the gas pressure. There is a more advanced longer lasting stainless steel injector, which I have on this 31. This type of injector is what is used with natural gas installations, which do not have Liquid petroleum but highly compressed natural gas (a silly idea as the system is much heavier and more expensive).
As far as I know, with Australia's safety regs, among the highest in the world, there is nothing that can go wrong with the feeds, without the system alarming or shutting down. There can be a slow leak somewhere of course but you can smell that if it is happening, because of the terrible smelling agent that they put in the naturally non odorous LPG as a safety factor. If there is a fast leak the feed system shuts off automatically.
There is a setting in the LPG computer that allows you to program Petrol into the combustion chamber along with the LPG to help the burn rate under full throttle. This is what most of the high powered Holden special vehicles do to get max power from their big V8s. It doesn't seem to make any noticeable difference to my car when I have programmed it in, just uses more fuel. It is not programmed to come in at the moment.
The guy who did the install is in Melbourne and has 25 years of experience as a major LPG installer. He is very accommodating but has not been able to solve my problem. He has had a number of goes using "team viewer" (a program that allows someone else to take control of your computer over the internet) tuning my system via my laptop.
So there you have it. Anyone else is free to comment if you know more about LPG injection and if you think I have misrepresented the system in any way. cheers
Saturday, December 14, 2013 - 12:36 pm, by: Dave Rose(Sand_groper)
Copper plugs !! As you know John its harder for the spark to ignite gas, in fact they even make HT leads for gas engines for this reason ! copper would have less resistance so this may be a marker of some sort ? i used to have Challenger on gas and ran it to long on gas ,petrol injectors got gummed up through lack of use and every time i nailed it it miss fired ! took weeks running petrol to clear it .
John Stafford DieHard Qld. Soarer UZZ31 GT-L V8 and a UZZ32 # 514
Saturday, December 14, 2013 - 01:03 pm, by: John Stafford(Johng12)
thanks for that page Tom, I have read it a number of times before and just read it through again to be sure. It emphasises a number of things that are peculiar to old mixer systems rather than vapour injection, also references problems that come with cold start weather. But there is plenty of good stuff there for those who are not mechanically oriented. Nothing for me there though, except that he does say that NGK is the right plug, copper plugs, which I have in it at the moment but the best are the top of the range Brisk silver plugs, best conductors and help the slow to burn LPG, giving your better economy and more power. They are not able to be reset and are made for LPG expressly, best money can buy. The Ford LPG plugs are platinum and do not ignite as well as copper or better still solid silver electrodes, but they do last longer with the heat. Iridium are said to not last too long but I have them in my 32 until they wear out. They are working fine for me there.
Actually I haven't noticed the difference between copper and silver on the 31. Maybe a little better economy with the silver?
I have had my petrol injectors out in both cars recently and put new seals in them and they are whisker clean. No issues there as I use petrol enough to keep them clean. I also run Flash-lube injection on the 31, which keeps the injectors clean too.
Tuesday, December 17, 2013 - 09:27 am, by: Tom Richards(Tomr)
john, would "The more fuel I put in (LPG that is) the better it goes. " indicate a leak somewhere around the injectors even though you cannot smell it??
John Stafford DieHard Qld. Soarer UZZ31 GT-L V8 and a UZZ32 # 514
Tuesday, December 17, 2013 - 09:48 am, by: John Stafford(Johng12)
Just saw that I missed one of your questions on the 12th Dec post asking if it was the same car that I replaced the O2 sensor wire? No. That was on the 32. this seemed fine on the oxy sensor wire, not burnt through. I put a wire to the Oxy sensor wires where they went into the ECU and put my multimeter on the wire and to earth to see if the sensor was working ok and it was, sweeping from low to high 0.4 to 0.8 of a volt consistently.
No leaks in the LPG as far as I can tell as if it leaks you can't miss the smell. I have had leaks with loose clamps at times and it stinks.
I think that with more fuel (LPG) I do not have to put my foot down so far and so the phenomena of dying does not occur so markedly.
I am having a week off so will probably take the cats off next week sometime.
John Stafford DieHard Qld. Soarer UZZ31 GT-L V8 and a UZZ32 # 514
Tuesday, December 24, 2013 - 04:28 pm, by: John Stafford(Johng12)
Wow, just shot my last arrow and it didn't hit the target. Still have the miss and maybe worse if that helps us think of what it might be. I just fitted 2 new stainless hi flow cats into the system and it seems to want to rev quicker, should be expected with better flow out the exhaust, but the dying is just the same, only comes in a little more easily due to the freer revvingness of the engine with the less restrictive cats.
Ok, now the question: where to from here?
Has anyone near me got another 31 ecu that I can try out?
John Stafford DieHard Qld. Soarer UZZ31 GT-L V8 and a UZZ32 # 514
Wednesday, December 25, 2013 - 06:21 pm, by: John Stafford(Johng12)
I was just looking at the engine with my son in law, a heavy machinery auto electrician and he found some wires that linked the petrol injectors to the LPG and it looks as though that may be the problem area as the LPG gets is signal from the petrol injectors, thus linking the 2 together and maybe explaining the reason for the miss on both systems.
We will put all the wiring for the injectors out on Monday and redo it more cleanly and without stressing it like the installer has done. Here's hoping we have finally found the problem.
I have noticed that whenever it starts it stumbles , but then seems to clear itself. This made me suspect the injectors or the electrical side of them anyway, as they seemed very clean when I had them out.
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