VIOLENTLY cutting out.....

[kayarubin]

hey guys. just a question. i bought an 88 model vr4 j spec the other week and it keeps violently cutting out at about 4200-4600 pretty much every time its moderately cold outside. im talking 20-22 degrees tho. sometimes it does it when its warm, but not as much as when it gets cold when the engine is up to operating temp, i live in darwin too. it only seems to do it on max boost after being loaded for 2-3 seconds, and it doesnt do it in 1st or 2nd, 3rd 4th and 5th it seems to whenever its been on boost for that amount of time. i'm really puzzled about what is happening. i've swapped to my yellow top injectors and put relatively new spark plugs and leads in. the plugs are a fairly even yellow/brown colour after giving it shit for a couple of gear pulls and shutting it off (not too good for my turbo i know) but yeah. do you think it could have some case of a severe detonation? i'm using 95 octane with octane boost, so it couldnt be the fuel. its got popping noises coming from the intake too......
i also think it could be using the waste spark (considering they use waste spark system e.g. 2 coils...) to ignite some un burned fuel left in the combustion chamber?

another thing would be that maybe the crank sensor is periodically advancing the timing so much it starts igniting the fuel really early? or the plugs could be a little hot and are doing that? theyre bp6es's.... should i try 7's maybe?

i'm stumped as to what it could be! any help would be GREATLY appreciated, i dont wanna end up bending a rod.

cheers boys and girls! kaya.

 

[brisvr4]

What you have there is what some people call boost cut or fuel cut.
It has been so long since I experienced it I can't really remember what the ecu cuts. It may be fuel or spark or both?
It generally feels like you have slammed on the brakes when it happens!
A well written chip can dispose of it as long as you have a single board with an eprom in it.

 

[strudle]

i had a very similar thing happen to mine. only happened under load. experienced a lot of what your discribing. I changed the spark plugs and the leads over and it fixed everything i was having issues with.
Try checking the leads with a multi-metre if ya got one on hand. See how they are behaving.

saying that theres probably quite a few other reason it could be doing that aswell.

 

[CLuTZ]

Firstly, what mods do you have on it, and what boost is it running?

What did you do to compensate for the larger injectors?

Has it always been running like this since you got it?

 

[kayarubin]

its bog stock. the ecu is an 8618 dual board, stock boost, stock airbox, stock exhaust etc etc, i havent done anything to compensate for the bigger injectors... am i supposed to? i thought they were straight bolt in.....?

but yeah. i've retarded the timing to 5deg btdc. havent had a prob yet. but i'll wait and see if it does it at night. it was doing it really bad when i first got it. as soon as it hit boost it just started spluttering and carrying on. but now its alot more violent. like slamming on the brakes... as brisvr4 said. but as i said i have changed to newer sparkies and now it doesnt splutter, it just jolts the whole car.

i do have an rs ecu here. but i put it in and it wasn't idling or running well when driven normally. i put this down to pretty much all the devices on the intake manifold being different to my rs engine.... :?

anyway. keep the ideas coming. cheers guys.

 

[CLuTZ]

You cant just throw some larger injectors in there and expect the ECU to know that you have done it. All that will do is make it hell rich.

If its bog stock with no mods- I find it hard to believe that it's hitting boost cut. I have a feeling you have a boost leak. Double check all your intercooler pipes to make sure they are on properly and the flexi ones aren't split. Also see what the seal on the J-pipe (first pipe that comes out of the turbo) is like, and if thats fine aswell, then i'd suggest swapping b.o.v's cos that could be leaking.


dre

 

[MDK87]

Sorry for the off topic question, but what is a waste spark system?

 

[CLuTZ]

Sorry for the off topic question, but what is a waste spark system?

http://tinyurl.com/4dhfg3

 

[kayarubin]

ok no probs. i'll check my bov and pipes out. thanks mate.

 

[VR-4Squid]

There's 2 wires in the ecu plug that need to be swapped when running a facelift ecu in a pre-facelift car.

www.vfaq.com has the answer (look for 1G ecu pin-out), it's simple to do, and simple to change back also.

 

[mattrat]

i have same problem as you, running 510's and its splutters hell on boost as its just runnign so rich, also my oxy sensor is fucked which causes it to run rich all the time aswell.
im chaning my injecotrs back to 450s and my oxy to a new one and if it works out then ill let you know.

 

[kayarubin]

problem found i think. wastegate was rusted closed.... :roll: lol. so it was running as much boost as the stock zorst could take! :shock:

i have since semi loosened it. but am yet to get it on boost for long enough.

 

[brisvr4]

I win! :smt038

 

[kayarubin]

you do indeed sire!!