hey guys. i thought it was my spark plugs but it was obviously not after i changed them twice in the same day.

when my car hits 4500rpm it begins to back fire then as it passes that rev range its fine but occasionally it does it at higher RPM.

i took the car today to get it checked on the dyno and there was no problem with the tune. i was told that it could be the leads so i changed them and still was the same thing.
so then after trying that i was told its either the computer has got a fault in it or it is the dizzy.

wat do u think the problem could be??

thanx Lenni

You could try closeing the plug gap up a little maybe?

yeah ive tried gapping the plugs down. at the moment its got a clearance of 6 mil.

Has this just started?
What sort of ECU are you running?
Could be a dirty chopper wheel (optical) in the dizzy?

im running the microtch LT-10
its just started doing it. ive dismantled the whole dizzy and cleaned it and its still the same.

Try swapping the cas for another known working one.
Got a feeling its a CAS related drama.
L8tr
E

i was told that the mitsubishi magna fits on but all u gotta do is change the gear on the the end.

Not thew entire dissie m8, just the CAS itself.
L8tr
E

_____________________________________________
The older we get........the faster we used to be!

ive tried to find another fj20 dizzy but im having no luck.

ive already bought the Magna dizzy so i want to try that out becuase i called Stewart Wilkins and said thats wat he replaces them with. but im trying to figure out wats top dead center on the Magna dizzy.

U sure the magna Dizzy utilises the same crank angle sensor M8?
New CAS's for FJ20's are readily available from any EFI components/parts suppliers.
L8tr
E

do u have any idea of wat store sells the CAS's.

if u do please let me know ASAP. its very urgent

thanx Lenni.

Petroject
Just take your dissie with you.
This cas is very common, same as Pulsar Turbo ET and some VG30 V6's.

Even if its not your drama, its handy to have one spare.
I have personally fried 3 in my Pulsar Turbo and one in the FJ20et in the last 5 years.
L8tr
E

thanx man for ur help i appreciate it

Lenni

i ended up buying a new CAS but its still got the same problem.

any other suggestions????

Process of elimination M8.
Try a different coil, trigger transistor, dizzy cap, dizzy rotor and so-on. You can use any 12v coil, Just eliminate your coil as a suspect.

Unplug and replug your ECU plugs numerous times.
Same goes the AFM connections.

I cant believe that the dyno mob couldnt pinpoint the issue.................
It should show up like dogs balls.

L8tr
E

well the thing is that im using 4 coils pack. the dizzy is only used as a crank angle sensor. i cant think of anything else but the computer. maybe it needs to be re flashed.

What ECU are you using?
L8tr
E

_____________________________________________
The older we get........the faster we used to be!

im running a Microtech LT-10 with the X4 ignition module

Have you checked your dwell time parameters to make sure you have enough dwell time for the coils you are using.
If they are Bosch electronic coils then you need 3.5 Ms dwell. Microtech X** modules are "dumb" so this parameter must be set.

Is your positive side power supplies sufficient to maintain voltage?

Is your CAS wiring shielded along its entire run?

Does the coil wiring or plug leads run close to the CAS wiring?

The list is endless M8.

Just keep substituting bits until you isolate the gremlin. Go back to a single coil, transistor and plug leads to rule out the 4 seperate coils or the X module.

I still cant believe your dyno man could NOT find an issue with it tho.
Id not be using that dyno man again if so.
L8tr
E

ive got no idea on how to check the dwell time parameters.

the power supply is sufficient.

the coil wiring is no where near the plug leads.

its just a headache to do.

it has to be something up with the actual computer. i was speaking to another guy thats got a microtech and he was telling me that the drivers began to stuff up one after another and he took it bak to microtech to get it fixed. so im hoping its just a computer re flash.

Ahh well, Sry M8 ur on ur own now. Without having the car at hand i can only even begin to speculate.
Good luck
L8tr
E

_____________________________________________
The older we get........the faster we used to be!

thanx mate for all ur help. i honestly appreciate everything uve helpd me with.

thanx
Lenni

Easy as M8
Id still be wary of what that dyno mob had to say.

Any missfiring issue would show up like dogs balls in the form of spiking low EGO's if it were an ignition miss (unburnt fuel) and spiking high EGO's if it were a fuelling issue, Ie too lean and missfiring that way or a CAS failure.
In your case you now knopw its not a CAS fault.
Dont sweat that tho M8, Those Nissan optical cas's are historically (relatively) unreliable and sooner or later, you WILL have one fail.

If you can beg/borrow a Microtech hand controller, you can have a look at your fuel and ignition settings to see if anything is untoward.
Same for the ignition config settings which I mentioned earlier and see if the coil dwell (charge) time is at least at 3.5Ms
I wonder if the ECU has decided to remove some fuel around the rev range your having difficulty with via the WOT settings??
On 2 occasions, I have had both my Microtech MT-8's mysteriously change some of their settings on their own. (NO hand controller connected)
Nothing major mind you, but enough to cause some weird running and be of a concern.
Id just restore the tune from the latest MEMCAL save and away itd go again.

Ive had in the past mystery missfiring which, looking at the EGO behaviour, I was able to determine it was a dying CAS.
It was cutting both fuel and ignition for less than half a second or so intermittently, running multiple coils. No amount of stationary running when I got home would re-create the cut.
The EGO's went skyhigh during the missfiring event.
Had it been an ignition fault (dying trigger or coil), it would have spiked to low EGO's (unburnt fuel) and I would have discounted the CAS.
I use one of those cheap 10 led bargraph type ego meters from Jaycar.
They are of little use for tuning, running from a narrow band ego sensor which has totally inadequate EGO V's voltage output to be of any use, but invaluable in diagnosing faults between ignition and fuel systems.

Anywhoo good luck M8.
L8tr
E

ive got a hand controller but i cant find it. i must of hid it somewhere.

i wouldnt want to play around with all the setting coz i wouldnt have a clue on wat im doing. ill let u know how it goes when microtech open, hopefully they can sus out the problem.


thanx
Lenni

have a HAPPY NEW YEAR

i sent my computer to Microtech and they said they couldn't find any problem with it. so it looks like im back to the elimination process again. i hope its one of the coils that have let go.

Just curious when u say missfire. do u get a load of black smoke out the rear? and out of curiosity what leads are you running?

it continually backfires at 4500rpm with black smoke and flames coming out of the exhaust. ive got 10mil leads some racing sort. ive changed the leads to thinner insulated ones but the problem still occurred. i just need to send it to a tuner with an oscilloscope so they can diagnose the problem. thats my last option.

Have you checked the mode of the Microtech ? If it was tuned in matrix mode but has been set back to the normal mode (whatever that is called), it will do exactly what you are describing. It happened to me and I couldnt find anything wrong with it either. Checked everything. Even had the LT10s, igniter and coils checked by Microtech. Nothing wrong with them. Finally took it back to the guys who tuned it and they spotted the problem in about 2 minutes and had it running perfectly again. Must have happened when I was fishing around in the progamming software. Made a mental note to leave it alone in future.

lenni
location

I found out from another site where your from.
go to Castle Hill Exhaust. 9580 2777.
ask for the Dyno guy, I can't think of his name
he is on the admin of the microteh site and the dealings I have had with him have been very good.
I'm sure he can solve your problems.
I also have had two mandrel bent car exhausts done there as well. one a fj turbo bluebird and the other a BA V8 ute
so the exhaust side do a good job as well and the price was very cheap

He has already been there, they couldn't fix it.

Try Yavuz at UNIGROUP 02 96312470


http://www.unigroup.com.au/contactus.htm


Peter

You should try PHIL at ULTIMOTIVE in BANKSTOWN, i go to his WORKSHOP all the time and i always see FJ20's in there....He is really good with them and will be able to help you fix YOUR PROBLEM....If you want call him and talk with him on (02) 9791 1388

ultimotive would be a waste of time and money

my gemini ultimotive did has never run better

I've been having a think about this:
Get into your Microtech and have a look at the BOOST CUT function.

I have had some mysterious misfiring dramas on my FJ 20 a while ago that i could not explain and about at the same RPM.

I found that the BOOST CUT function I had set was causing the drama.

I had set the figure at about 2psi above the boost pressure setting i was using and it was too close and causing an issue.

I increased the setting at least 4 psi above boost pressure and the drama went away.

L8tr
E

how u going?

my boost cut was set to OFF when this problem occurred but the problem is still there.

i have an interesting question for u. i took my car to the entrance yesterday and i was on the freeway. i happened to give it full acceleration, when it hit high RPM the car cut out for a split second and the blow off valve released while my foot was flat on the throttle. its the 2nd time this has happened its very strange. its all got to do with the car cutting out but cant find the stupid problem.

Did you take it to Dale at Castle Hill like I said?
Hav youe done anything with the fuel system? What reg are you using? What injectors?
You might have a fuel presure problem, I had the same problem using a rising rate fuel reg as soon as the engine made boost underload the fuel pressure increased to far and caused the engine to missfire and dump a heap of carbon.
Sounds like the same problem I had

Youve eliminated everything ignition wise that could be a problem, Id suggest move on to your fuel system now, it sounds like the exact problem i had recently and i chased it around for hours only to find it was my adjustable reg was set too high static pressure.
If you want to try a standard reg ive got one

ive taken the car to Dale twice and it came out with a fresh tune the 2nd time and still he couldnt pin point the problem.

the fuel pressure was cheked and its fine.

its all fixed guys.

turned out it was the TPS. it was reading 3% when the throttle was open half way. so the sweeper arm was changed inside. u weren't able to pick it out the increments on the laptop though.

thanx to Justin at BLACK TRACK Performance at Thornton. had the car bak 2 days later.


thanx for all your help guys, its appreciated

thanx
Lenni

hi lenni do you have a contact number for justin at black track porformance, and if you dont mind me asking roughly how much did it set you back cheers, drew

BLACK TRACK Performance- 02 4966 1235


i got a new TPS fitted, fixed the power source to the computer coz it was getting low voltage, extra earth straps to the motor were put on and a re-tune all for $800

tell him Lenni with the 180B sent u.