I think my engine is missing / not enough fuel to a cyclinder?

[Caleb 895/1000]

OK so i replaced my spark plugs AFM and fuel filter and when ever i hit boost my car runs rough and black smoke comes out the back... what would be my next step in locating this problem, i have a 97 wrx sti V4

[Koom]

Boost leak? Black smoke could be showing that its running rich.

[Caleb 895/1000]

I have been looking through other peoples posts and someone sed it feels as though the car is being held back lowkey?

I dunno its hard to explain. Im in auckland this weekend and all of next week. If some one can help me im sure i could find them a cold doz of pures or something.

I would rather the problem fixed before i head back to palmy..

Thanks heaps

027 780 3945. I also have an 021 but dont know the number. If you have a 021 txt ma 027 and ill continue to txt over 021

[Caleb 895/1000]

Yea ive been told its running rich but wouldnt know what to do after what i have already done.

I have given it a comb over for boost leaks twice and have come up with nothing

I have exhausted my automotive knowledge and may have missed a hose or pipe somewhere im not sure... Il have a look again tonight

[Koom]

Atmospheric BOV that leaks under boost?

[NotAWhiteGTB]

How long has it being doing this for? Did it start doing it all of a sudden or gradually got worse and worse?

When it does run rough, do you mean it gets really jerky/shuddery? Doesnt have as much power as it normally does? does it do it on any amount of boost or just when it starts getting closer to max boost??

[Guest]

Where abouts are you in auckland???

I'll be at home doing an engine build all weekend so can take a look at it for you for free... I'm out west if you want to drop by, PM me or text... 021 244 6724

[Swindog]

Did you put the fuel filter in the right way round?

[Guest boostin]

Tried an AFM??

[Caleb 895/1000]

It started doing it gradually.

Only does it at boost over 10psi. real bad at 20psi

[Swindog]

NOt a leaky lead or some such? Is it fuel or spark miss?

[Caleb 895/1000]

I dont knw. If its fuel or spark... Im sure fuel filter is on the right way... Could it possibly be fuel pump?

How do i check the bov is not leaking?

[dubbedup]

 Caleb 895/1000 said:

I dont knw. If its fuel or spark... Im sure fuel filter is on the right way... Could it possibly be fuel pump?

How do i check the bov is not leaking?

vacume/boost gauge

and do a quick double check on fuel filter...

[Koom]

 Swindog said:

NOt a leaky lead or some such? Is it fuel or spark miss?

Whats your plug gap's like?

[Caleb 895/1000]

The gap is .75mm on the plugs, im replacing the leads tomorrow as mine are looking not so hot, the filter is on the right way,

If the leads are not the problem what would be my next step?

Thans so much for all your input also... Much appreciated!!!!!

[Guest boostin]

How much boost is it running? It could be blowing out the spark.

[Koom]

 boostin said:

How much boost is it running? It could be blowing out the spark.

I concur. I had to close mine down from 0.75mm to <0.6mm to get over 20psi into my engine.

[Swindog]

Need to isolate it to a spark or fuel issue.

If your new leads dont cure your problem may pay to go get a fuel pressure test done.

Systematically tick off the options. Loose or cracked vacuum hose, plugs/leads, fuel system.

[Guest]

I've had a bit of a miss under boost too, only happens sometimes though, just had new sparks put in

[Koom]

 JORDI said:

I've had a bit of a miss under boost too, only happens sometimes though, just had new sparks put in

At how much boost and what plug gap though?

[Guest]

Its running standard boost its a 95 wrx, so its like 8psi or something I think, and how do you check plug length exactly?

[Koom]

 JORDI said:

Its running standard boost its a 95 wrx, so its like 8psi or something I think, and how do you check plug length exactly?

To check plug gap you pull them out and measure the gap of the electrode. At only 8psi its more likely to be bung coils or afm or similar.

[Guest]

The electrode huh lol.. Yea well I got told thats around what they are standard boost, correct me if I'm wrong.. Sweet, yea thought it might be coils are they expensive, hope I'm not thread snatching btw, got the same issue

[Guest boostin]

 JORDI said:

The electrode huh lol.. Yea well I got told thats around what they are standard boost, correct me if I'm wrong.. Sweet, yea thought it might be coils are they expensive, hope I'm not thread snatching btw, got the same issue

Similar issue, not the same. I reckon your coils are stuffed. Pull them back out and pull the rubber boots off the tips. You'll find the plastic underneath will be cracked.

[Caleb 895/1000]

I changed the gap to 0.6mm no difference. It does it on 11psi and worse on 18psi.

Im just going to go to subaru and let them find it.

Ive spent over a grand and nothing has worked