Injector shenanigans

Fluffy282

Fluffy282

New member
I'm not really sure why I didn't post here a while ago.

Starting last fall my car has had a stutter or surge . Afrs fluctuate violently... Only under acceleration, seems to be more pronounced when it's cold.. I figured it was a vacuum leak, traced down some minor leaks, no major results. So my next thought was injectors, so I upgraded my injectors, still no good. Thought maybe it was in the tune. Went to Bren and put it on the dyno (don't get me started with my experience there) what they said was 1 injector was improperly installed and they could watch it suck air and shut off under hard acceleration.

I'm no expert, but if there was a problem with injector fitment wouldn't there be a fuel leak? What are the chances my stock injectors would BECOME unseated and my aftermarket injectors installed wrong? Could it be an issue in the fuel rails themselves?

 
drvsdwz

drvsdwz

DRiVe SiDeWayZ
Not necessarily. If it is seated properly in the rail and tilted ever so slightly in the tgv housing, you can have a vacuum leak there with no fuel leak. Maybe an o ring was pinched?

I actually decided to install my dw1000 since I haven't been able to sell them so I can get the 200 for the old ones.

Anyways my car was idling fine after I changed the tune, but while accelerating, it would hitch. Turns out my injectors were not seated properly. Another thing I did was the "stumble" fix when right around 3k it hitches.

 
Fluffy282

Fluffy282

New member
Yes, I guess the plugs were pretty well shot which is odd cause they only have about 25k on them but they'll be replaced. See if that helps.

 
B

blmpkn

Pascifist Patriot
Not to hijack, but would the stumble in my obxt be related to Matt and Justin's? Happens randomly right around boost. Mostly with low throttle input but she comes out of it with a little bit of a heavy foot. Doesn't happen all the time either, haunted?

 
xxnightraven73x

xxnightraven73x

^who i am ...what i say --->
They all had an odd angled burn/wear to them which would easily double or triple the gap if the spark is blown to that side

 
Fluffy282

Fluffy282

New member
Misfire moved, so looking at a coil pack now. Also have a 4.0-5.0 af correction at idol... So maybe tracking down a boost leak.

 
Industry

Industry

New member
Would they all being burnt to one side indicate a slight timing issue? Like a valve opening early, or staying open too long? Just an idea.

 
drvsdwz

drvsdwz

DRiVe SiDeWayZ
So update on mine. Got rid of all stock fuel dampers and the regulator. Got some injector clamps, and a 2006 STi fuel pressure regulator.

Stumble eliminated. All it took was changing the supply line to the rails, and the return line from the rail to the regulator and the regulator to the firewall

 
Fluffy282

Fluffy282

New member
I've got it down to a misfire on cylinder 4 only.... New plugs, new coils, new fuel system, compression tests at 150lbs. I'm stumped. Guys at kinetic said next step would be to check timing and then valves...

 
RyanR

RyanR

///|||\\\|||///|||\\&#092
Are you missing spark or fuel when it misfires?  (does it run rich or lean)?  Is the misfire only under boost?

I'd recommend:

1. Check and set spark plug gap on the misfiring cyl.  I've seen new plugs come improperly gapped, which can cause the spark to "blow out" under boost.

2. Leakdown test.

3. Check tbelt timing while doing leakdown since you're there.

4. Intake manifold leak test.

5. Check for exhaust leaks at the header, and beyond.

6. Check grounds for injector/coil/ECU circuits.

7. Check that the primary O2 sensor is in spec.

8. Check that the MAF sensor is in spec, clean it.

9. Make sure the pins for the misfiring cyl coil pack connector are not foobar'd.

10. Drink beer, cry, and apply money for a shop to figure it out.

 
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