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R34 Rough Idle, Misfiring, Running Rich?

MarkB34

By MarkB34,
in Engines & Forced Induction

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MarkB34 Rookie

MarkB34

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Hey guys, this is my first post here but I've been reading for weeks now as I've been doing a complete engine swap on my car. Great to finally be a part of the skyline community

 

I bought my 2001 R34 GT about 3 months ago, and a month ago the radiator dumped coolant and the engine overheated and warped (didn't change temp gauge at all), and the car shut off completely and smoke billowed from engine. All sorted now with new engine in and everything seemed to be running fine. Took it on a long run 2 days ago and no issues at all, and everything seemed perfect minus the need for a tune. Last night I took it for a run on the freeway and I noticed that the tacho was pretty erratic jumping  about +-700rpm and a loss of power so I pulled over and the car shut off before I stopped and lost power steering similar to when the engine went. I managed to get a tow home and today I checked the plugs (all new from swap), and coilpacks for any damage (not sure if these are stock or not as they are blue, possibly Spitfires?) and didn't find anything. On idle the car is super rough misfiring and jumping around revs, when revving the car evens out at about 3000+, but backfires on decel and idle, even a little around 3000+. I tightened all clamps behind AFM (replaced old one with one from wreckers due to swap) and plan to swap back to the old one tomorrow and check if that fixes anything and also clean out the O2 sensor. Could the issue be a faulty injector possibly? 

Would connecting a scanner to the car produce any possible fault codes? Or would it just read no issue? 

The only thing I can think of in between it being perfect and the issue arising is that the car was washed but I doubt much water found it's way under the bonnet and the car ran fine for an hour or so afterwards. 

Thanks guys any help would be greatly appreciated.

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Slap Rising Star

Slap

Posted
Posted

Could water have got in the tank.
Sounds like closed loop o2 to ecu isnt functioning correctly.wrong a/f mix readings.
By 3k its hittin maps usualy.
If its stock ecu unplug the o2 sensor leave it and do a reset and start it to see if idles and revs to 3k better.
Could be dirty maf also

Any mods we should know to help internet diagnoses?

MarkB34 Rookie

MarkB34

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Posted (edited)
9 hours ago, Slap said:

Could water have got in the tank.
Sounds like closed loop o2 to ecu isnt functioning correctly.wrong a/f mix readings.
By 3k its hittin maps usualy.
If its stock ecu unplug the o2 sensor leave it and do a reset and start it to see if idles and revs to 3k better.
Could be dirty maf also

Any mods we should know to help internet diagnoses?

I heavily doubt water would have made its way into the tank

I'll give the O2 sensor a go today, cheers. I'll replace with the old AFM and clean the plug today too. Cheers mate

The only mods are a pod filter (have the airbox also, if that would possibly make a difference?) + a cat back exhaust. 

 

I reckon I've found the issue mate, the CAS disc was snapped and bent all over, I'm not sure how it happened though, would you know any causes? 

IMG_20190610_114158_01.jpg

Edited by MarkB34
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MarkB34 Rookie

MarkB34

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5 minutes ago, Slap said:

Wow. I havent seen that before. Definitely an issue. I cant believe it ran clear at 3k.

Unless you broke the disc by accident opening it up. ( doughtful ).

Got another cas?

Me either, I am shocked that it didn't run worse. I've ordered another one, should be here mid week, just concerned it will happen again. Definitely will get it tuned asap, to be sure

Thanks mate

Slap Rising Star

Slap

Posted
Posted

Stock ecu should just need a reset unless u got nistune in it.
Have you driven another turbo skudline?
If not maybe it wasnt running correct at 3k+ and never experienced its hidden truth.

I just cant see it running right at all if that disc was like that the whole time.

New cas . Reset . Away you go hopefully. Goodluck! And becareful cause it may have loads more power than previous.

MarkB34 Rookie

MarkB34

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I doubt the car has a nistune, I've already reset the ecu before and everything ran fine. I haven't driven another turbo skyline, but I'm unsure as the CAS seemed in pretty decent nick when I first looked at it

Hopefully when it arrives I can just plug and go, straight to the tuners. Cheers mate, you too

Slap Rising Star

Slap

Posted
Posted

You cant tune the stock ecu.
You will need an aftermarket one and if your auto one that can assist the auto.

I doubt the car has a nistune, I've already reset the ecu before and everything ran fine. I haven't driven another turbo skyline, but I'm unsure as the CAS seemed in pretty decent nick when I first looked at it
Hopefully when it arrives I can just plug and go, straight to the tuners. Cheers mate, you too
MarkB34 Rookie

MarkB34

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Okay, so I replaced the CAS tonight and the car ran and made it around the block, the timing is slightly off as it has a rumble quite low in the revs and on takeoff. Will adjusting the positioning of the CAS make a difference or should I wait until I get it to a tuner to go over it properly? 

Thanks again guys

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