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Old 29th July 2011, 01:36 PM   #1 (permalink)
leeroy_25 is Chuffed to nuts the RB30 lives!
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Dropping a bit of a cylinder?!

Okay.. yet again I seem to have a small issue with my car not running cleanly.. It is only really noticeable at ideal but it seems to be partly dropping a clyinder in and out. Under load and rpm it seems fine.. Maybe feels a little flat but I have just connected the 4WD back up.

I used an infra red temp guage on the exhaust manifold and it seems to show no.1 is running a good bit cooler than the others. Could be just due to it getting some air from the fan? the rear are running slightly hotter which I guess is fairly standard?

After my last problem the first thing I did was a compression test and even though cold it was all good and strong readings.

What else might suddenly go and cause this running problem and not make it miss or anything under load? Weak coil? dodgy ignition box? Bad earth?
Too rich or lean on idle?

Please help.

Thank you
Lee
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Old 29th July 2011, 03:58 PM   #2 (permalink)
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I would check both fuel and ignition parts.
Fuel: injector, maybe a glitch in the coupler?
Ignition: sparkplug, coil, coil harness, ignitor, cas...
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Old 29th July 2011, 04:14 PM   #3 (permalink)
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Mine had the tinyest of missfires on ideal and totally unnoticable when throttle was applied and was fine for a year, turns out the ringland had gone on number 6.

As yours is cold on number 1 though I suspect its probably nothing worse than a plug or coil breaking down slightly - easy job first, check the plug gaps
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Old 29th July 2011, 07:08 PM   #4 (permalink)
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I looked at the plugs the other day.. They looked okay other than black!
I compression tested it as well while I had the plugs out and all were well up in the green and pretty even across the board. And that was cold.

For sure it is rich generally but looking at the map the tuner has pulled a lot of fuel out in this area so maybe it is too much out?

As for the #1 temp reading on the manifold.. I am thinking that might be more down to cool air from the fan? I could try swapping the coil packs around or borrowing one from somewhere.

Such a PITA!

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Old 29th July 2011, 07:11 PM   #5 (permalink)
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Would I be correct in thinking if I pull all the plugs and can earth them in the coil packs. if I spin the CAS it will spark? might be able to visually see a weak spark??

Cheers
Lee
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Old 29th July 2011, 10:50 PM   #6 (permalink)
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Put the plugs in the coilpacks and ground all plugs. Should give a goodwill spark.
If running too rich you will get bore wash, that will damage bore, pistons and ringsted.
if one cylinder is slightly rich, it could be a faulty injector.
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Old 30th July 2011, 10:25 AM   #7 (permalink)
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Thanks for the info. Is there an easy way to check the injectors?
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Old 30th July 2011, 10:29 AM   #8 (permalink)
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You can try changing the injector between the 1st and the 2nd cylinder and see if the problem then moves to 2nd cylinder.
The same goes for coilpack.
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Old 30th July 2011, 05:55 PM   #9 (permalink)
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That assumes the manifold temps change is not due to the fan?! Will give it a go though.. Easiest job would be swap a good set or coils on.. See if it cures it.. Then swap something else if not!
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Old 30th July 2011, 06:46 PM   #10 (permalink)
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How many O2 sensors are you running and what ECU are you running?

Also, whats your idle speed? Are running your ICV, the thermostat one?
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Old 31st July 2011, 05:59 PM   #11 (permalink)
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Hi There, I am running the two Factory O2 sensors but they are switched off at present? The tuner did that for some reason.. I think they were both giving slightly varying readings. I have an Apexi ECU.

Idle has dropped sine it was mapped recently without touching any adjustment. it idle around 850-900rpm and sounds quite cammy which it didn't previously. Sounds nice! but I gather that is a symptom of being too rich or to lean but I cannot remember of find which!

Which is the thermostat ICV? The one with the idle adjuster screw?? I think I have all the factory Idle control stuff still attached.

Thank you
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Old 31st July 2011, 10:04 PM   #12 (permalink)
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The ICV is the one without the adjuster screw.

I have the same issue, but I know the front O2 sensor is knackered.

The AFR voltages are slightly different too. I need to investigate that.

I will be changing it and hoping for some improvement.
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Old 1st August 2011, 02:06 PM   #13 (permalink)
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Oh.. Let me know what you find! I guess I could try switching on my O2's to see if it helps?

So the thermostat ICV I am still not sure? Is it the square one that sits right in under the plenum? Has 1 plug going to it..

Hope I can sort it out soon... Quite strange you mention that ICV which ever it is.. maybe you can post a pic or a diagram with it in.. I am sure the car was okay when I left the dyno.. But then is was red hot.. Since I have driven is since on smaller shorter runs with a lot more cruising is when the problem seems to have occurred..
We had to adjust the airtemp correction value up on the dyno so this did not kick in until 50degs as the air temp as getting up around 45-48degs and if you didn't take out the correction it would put more fuel in each run to compensate and was imposisble to map! Maybe that has caused a problem that when it's cooler it's now not fueling correctly be that rich or lean..

Anyway let me know what you find out.

Cheers
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Old 1st August 2011, 09:37 PM   #14 (permalink)
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Bit more info to add.. I went out and started the car this evening to see if switching on O2 would change anything. Not the slightest difference. However what I did notice was when I was when I let the car idle for a few seconds sounding fluffy (approx 850-900rpm).. after about 5 seconds the rpm slowly would rise up to around 150-1200rpm and sit there. Idle was cleaner when it settled there.. If you gave it a little rev and let it settle back it would drop back to 850-900 and then do the same again?

Does this give you any tips? Rich fuel mixture on idle and rising rpm due to excess fuel?

Cheers
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Old 1st August 2011, 09:46 PM   #15 (permalink)
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Interesting, my car did exactly the same today when sat in traffic.
I tried to remove the rear O2 sensor today, but the socket was not good enough.
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Old 1st August 2011, 10:13 PM   #16 (permalink)
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to me lee it sounds like its cracked a liner. water getting in,then when you start misfire until water has steamed out. runner on number 1 cooler? water possibly cooling it. sorry mate.
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Old 1st August 2011, 10:20 PM   #17 (permalink)
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whip number one plug out mate, turn motor over by hand until number 1 is at bdc. then cover plug hole to stop anything dropping in,day after get a bore scope and have a see if there is anything built up in there ref water,.
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Old 1st August 2011, 10:37 PM   #18 (permalink)
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Exactly the same? Is this on your Rb30.. Or do I remember you sold that.. The only two things I can think if u have not recently had a map leading to a rich or lean issue. Is an injector fault or weak spark. Let me know if u get anywhere. Why don't u try turning off O2 feedback to start?
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Old 1st August 2011, 10:40 PM   #19 (permalink)
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Sure hope not rockabilly.. Compression is all strong and not using any water that I have noticed.
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Old 1st August 2011, 11:21 PM   #20 (permalink)
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Sounds like it just might be too lean on idle , I always turn the O2 feed back on pfcs off too cos it's crap try adding a small amount of fuel to the map on the idle cells if u have a way of doing it and see if it helps
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