Jump to content
SAU Community

Recommended Posts

Hey guys,

Been trying to troubleshoot this issue which occurred one day while I was driving the car during the stinking 35+ degree hot weather.

My 1st cylinder is not firing at all. Some days it starts running fine and gives me false hopes that she's okay - the next day it f**ks around again!

I've tried the following things to rectify this issue:

- Replaced coil packs with brand new YJ coils.

- Replaced coil pack harness.

- Sent ecu to microtech to get to checked. It cleared the diagnostic tests.

- Dry compression tested the engine. Compression results were all within 3-5 psi of 150psi.

- Replaced CAS.

- Tested all ignition related wiring continuity. It all passed the diagnotic tests.

Some things to know about my car that relate to this issue:

- it has a microtech ltx12 ecu

- YJ coil packs.

I'm at a point where I've hit a dead end.

Does anybody have any decent advice they could give me?

Secondly is there anybody in Sydney that would let me plug their ecu into my car because I get this feeling that my ECU is screwed and it's not worth taking a gamble and buying another one if I can't confirm it's the issue.

Thanks in advance guys!

  • Like 1
Link to comment
https://www.sau.com.au/forums/topic/438150-cylinder-1-dropping-completely/
Share on other sites

sounds like you have eliminated compression and ignition, are you sure its specifically no1 cylinder?

have you checked your loom and plug to your injector?

what condition are your injectors in and do they need cleaning?

sounds like you have eliminated compression and ignition, are you sure its specifically no1 cylinder?

have you checked your loom and plug to your injector?

what condition are your injectors in and do they need cleaning?

Thanks for your speedy response.

I know it's cylinder 1 because when it's misfiring if I unplug coil pack 1 the misfire doesn't change.

I've replaced my injectors 3 months ago with brand new ones and also forgot to mention that I checked the injector plugs with a node light. I also used a stethoscope and could hear the injector ticking.

Other thing I should mention is that it's running extremely rich while the cylinder doesn't fire.

sounds like you have the basic elements of combustion

Possibly an ECU/ electronic issue man, the guys at UNIGROUP are very good at what they do, they should be able to sort it for you but they don't do it for free

Full list of mods:

- GCG highflow stage 2 ball bearing turbo.

- cam tech 256 cam shafts

- tomei adjustable cam gears

- supatech tech valve springs, retainers and stem seals

- blitz dual sbc boost controller

- microtech turbo timer

- gates racing belt

- microtech ltx12 ecu

- YJ coil packs

- Bosch 044 fuel pump

- five-o 660cc fuel injectors

- front mount intercooler

- arp head studs

- cometic mls head gasket

Also the head was recently serviced and had a mild polished.

I'd say that's pretty much everything that's been done to my car.

If Microtech have tested your ecu and can't find a fault sounds like you need a good dyno operator. it could be something else or maybe the ecu is failing under load conditions that can't be replicated on the test bench.

is any coolant leaking into the cylinder ? been told that that will cause a serious misfire

and is there defiantly fuel getting into the cylinder?

Edited by ..::R33GTS-T::..

Well I spoke to my tuner and he reckons the bench testing isn't a good indicator as its missing the environment and load of a realistic situation.

If Microtech have tested your ecu and can't find a fault sounds like you need a good dyno operator. it could be something else or maybe the ecu is failing under load conditions that can't be replicated on the test bench.

How could I definitely confirm that coolant would be leaking into the cylinder. I've checked the coolant in the overflow bottle and radiator - fluid levels haven't change. Fuel I can definitely confirm because of the tests I did on the injectors and secondly because the misfire is causing the care to run extremely rich.

is any coolant leaking into the cylinder ? been told that that will cause a serious misfire

and is there defiantly fuel getting into the cylinder?

I have a serie1 rb25det but the ignitor has been removed becuase the ecu I have has an inbuilt ignitor. Tuner reckons ignitor in ecu is probably screwed....

Does it have an ignitor?

I know it's cylinder 1 because when it's misfiring if I unplug coil pack 1 the misfire doesn't change.

What happens if you then swap #1 #2 coils? Does the failure follow the coil ie now #2 is failing, or does #1 continue to fail?

What happens if you then swap #1 #2 coils? Does the failure follow the coil ie now #2 is failing, or does #1 continue to fail?

Hey bud,

Misfire stays on cylinder 1. Doesn't follow coil packs or spark plugs.

Well I spoke to my tuner and he reckons the bench testing isn't a good indicator as its missing the environment and load of a realistic situation.

You can replicate anything given enough time. What exactly does he think can't be tested with regards to an injector?

I have heard of a few issues with five-o's lately, it would be the obvious next step to test the injector imo, unless it did the same thing on the old injectors?

You can replicate anything given enough time. What exactly does he think can't be tested with regards to an injector?

I have heard of a few issues with five-o's lately, it would be the obvious next step to test the injector imo, unless it did the same thing on the old injectors?

The tuner was referring to heat and vibration of the ecu unit as opposed to it sitting on a work bench. Reckons something could be getting hot and loosening up causing the igniter not to fire correctly.

With the injectors, I checked the plugs with a node light and also used a stethoscope to listen to the injector. Node light went off in the same sequence as the rest of the injectors and the injector also had a tapping noise in the same sequence of the others.

Is there anything else I can do to check the injectors???

compression tests can lie !!!!, when engine is cold remove radiator cap then start motor and see if air comes out through the radiator when the motor is missing

I have seen this happen, in very rare cases HG can seal at non operating pressures ( comp testing) but then "open" once the motor is at running pressures

compression tests can lie !!!!, when engine is cold remove radiator cap then start motor and see if air comes out through the radiator when the motor is missing

I have seen this happen, in very rare cases HG can seal at non operating pressures ( comp testing) but then "open" once the motor is at running pressures

I tried this - water didn't really bubble. A tiny amount of white froth developed as the coolant started to get hot. Not sure if that's meant to happen but I read up that it froths a little when the radiator starts to build up pressure.

Massive head f**k it has become!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • Lucky man, who owns it in the family? Any pics? 
    • The engine stuff is Greg Autism to the Max. I contacted Tony Mamo previously from AFR who went off to make his own company to further refine AFR heads. He is a wizard in US LS world. Pretty much the best person on earth who will sell you things he's done weird wizard magic to. The cam spec is not too different. I have a 232/234 .600/603 lift, 114LSA cam currently. The new one is 227/233 .638 .634. The 1.8 ratio roller rockers will effectively push this cam into the ~.670 range. These also get Mamo'ified to be drilled out and tapped to use a 10mm bolt over an 8mm for better stability. This is what lead to the cam being specced. The plan is to run it to 6800. (6600 currently). The Johnson lifters are to maintain proper lift at heavy use which is something the LS7's supposedly fail at and lose a bit of pressure, robbing you of lift at higher RPM. Hollow stem valves for better, well everything, Valve train control. I dunno. Hollow is better. The valves are also not on a standard valve angle. Compression ratio is going from 10.6 to 11.3. The cam is smaller, but also not really... The cam was specced when I generated a chart where I counted the frames of a lap video I had and noted how much of the time in % I spent at what RPM while on track at Sandown. The current cam/heads are a bit mismatched, the standard LS1 heads are the restriction to power, which is why everyone CNC's them to get a pretty solid improvement. Most of the difference between LS1->LS2->LS3 is really just better stock heads. The current cam is falling over about 600rpm earlier than it 'should' given the rest of my current setup. CNC'ing heads closes the gap with regards to heads. Aftermarket heads eliminate the gap and go further. The MMS heads go even further than that, and the heads I have in the box could quite easily be bolted to a 7.0 427ci or 454 and not be any restriction at all. Tony Mamo previously worked with AFR, designed new heads from scratch then eventually founded his own business. There he takes the AFR items and performs further wizardry, CNC'ing them and then manually porting the result. He also ports the FAST102 composite manifold: Before and after There's also an improved racing crank scraper and windage tray. Helps to keep oil in the pan. Supposedly gains 2% power. Tony also ports Melling oil pumps, so you get more oil pressure down low at idle, and the same as what you want up top thanks to a suitable relief spring. There's also the timing chain kit with a Torrington bearing to make sure the cam doesn't have any thrust. Yes I'll post a before and after when it all eventually goes together. It'll probably make 2kw more than a setup that would be $15,000 cheaper :p
    • Because the cars wheels are on blocks, you slide under the car.   Pretty much all the bolts you touched should have been put in, but not fully torque up.   Back them off a turn or two, and then tighten them up from under the car with the wheels sitting on the blocks holding car up in the air.
    • Yes. Imagine you have the car on the ground, and you mine away all the ground under and around it, except for the area directly under each individual wheel. That's exactly how it'd look, except the ground will be what ever you make the bit under each wheel from
    • Yes, if you set the "height" right so that it's basically where it would be when sitting on the wheel. It's actually exactly how I tighten bolts that need to be done that way. However....urethane bushes do NOT need to be done that way. The bush slides on both the inner and outer. It's only rubber bushes that are bonded to the outer that need to be clamped to the crush tube in the "home" position. And my car is so full of sphericals now that I have very few that I need to do properly and I sometimes forget and have to go back and fix it afterwards!
×
×
  • Create New...