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idle over fueling problem

S15AK

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I've had a problem for a while with my S15, it won't idle when reved. If I give it some gas when idle it will cut out, and it dose smell of petrol so guess its flooding. Driving about is fine, just struggle a little when coming to a stand still as it can cut out.

what we have done so far is

changed idle control valve
checked and fixed all boost leaks
injectors tested
smoke tested for vacuum leaks
compression tested
MAF been checked and cleaned
Ran with or without lamba sensor

nothing has made any difference...

Can anyone think of what else I can look at?
 

Max

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only other thing that would be a mega long shot is alternator. Saw a post on here when searching about this MAF problem leading to stalling when coming to a stop, which I occasionally have. Someone changed their alternator and it cleared up. Cant remember who though! Warrants more research though.
 
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i got a ssqv 3 hks dump valve on my s15 and before i had it mapped or anything else done to it it used to try and cut out, if thats of any good to you...... what bout air mass meters can broken ones course that problem, ill look into this more and see what i can find for you
 

S15AK

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cheers guys.. I am using an external wastgate setup so not bothered with a dump valve.

Top mount/T3 Turbo with T70 compressor
Top mount Japspeed Mainfold
External Wastegate

SS custom exhaust (with HKS Hi-Power back box)
Splitfire coilpacks
Nismo 555 injectors
Greddy Profec B Spec II
Apexi ECU
Apexi Power FC
Apexi Induction kit
Z32 AFM
FMIC
DB-Power Radiator
Walbro Fuel pump
 
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so how do you get rid of compressor surge? only asking about BOV as thats a easy way to over fuel at idle or after coming off load and having the engine stall, assuming that your tune is mapped for the surge to get redirected before the turbo but after the MAF, if you vent it you map will run rich once off load for a few seconds
 

S15AK

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I was just a cheap Greedy copy I found out after it had been mapped, I did ask if I took it out would it effect the map and I was told no..

Think I might know what's wrong now. Spoke to Greg at Pro tuner before (top guy), and he said with the top mount T3 and my MAF/filter sitting near the turbo, it can cause back air flow from the turbo, which will pass back over the MAF tricking it into thinking it is getting more air when the system isn't. I do now remember when I changed my hoses for some decent ones I found this thing shoved in my pipe which I thought was just a cheap tacky thing to give it better airflow or some crap, so through it out... However it dose actually diffuse the air flow going back over the MAF.

So will need to get something knocked back up and try that.
 
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Has this only happened since you got rid of that pipe insert, Adam? If so, there's a thread on sxoc that Vidal Baboon started about his problems, so he made a crusifix style insert for his intake pipe that solved the problem.
 

S15AK

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Don't think I noticed it straight away, but can't remember now. If this won't make a difference I will have to get it all remapped I think.

Thanks for the heads up Adam I will head over to sxoc now..
 
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A remap won't sort the problem, it's an air mass meter issue, if it's what has been mentioned. The stock afm setup isn't great and requires a ''turbulant'' affect through it, especially on top mount setups. I never had this issue as I ran a map sensor, thus deleting the afm all together.
 

S15AK

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Can you find that thread? The sxoc search is pants..

How much approx would it cost to go map sensor? Would I have to get rid of the power FC?
 
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I've read the thread several times over the years, I'll have a root around for you, mate. I'm unsure if you can convert the L jetro version to D jetro, which is what I ran. If I'm honest, the D jetro is a far better setup than the L jetro. It's a much cleaner setup, you get more functions, like inlet temp and you can pop a boost hose off (which never actually happened to me) and drive home with no problems, there's just no boost.
 

S15AK

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Cheers Adam..

It did fix it! can't beleive we've spent ages scratching are heads over this... Well Graham at DCMS has.

It was all my fault in the end.... another reason why I don't work on my car, as when I do stuff goes wrong!
 
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so for those of us that aren't going to read through the links, out of curiosity what was the problem & solution in the end?
 

S15AK

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What I said below did work.. we made up a waffle type defuser and put it in the hose between the MAF and the turbo to stop the turbo blow air back across the MAF..

I was just a cheap Greedy copy I found out after it had been mapped, I did ask if I took it out would it effect the map and I was told no..

Think I might know what's wrong now. Spoke to Greg at Pro tuner before (top guy), and he said with the top mount T3 and my MAF/filter sitting near the turbo, it can cause back air flow from the turbo, which will pass back over the MAF tricking it into thinking it is getting more air when the system isn't. I do now remember when I changed my hoses for some decent ones I found this thing shoved in my pipe which I thought was just a cheap tacky thing to give it better airflow or some crap, so through it out... However it dose actually diffuse the air flow going back over the MAF.

So will need to get something knocked back up and try that.
 
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