Bad Injector O-ring

[StealthX]

Hey guys...

I've had a shitty idle problem in the last few weeks, my car wants to idle around 3 - 3.5k rpm, almost uncontrolled and I'm pretty sure its a vacuum leak as my car is map sensored. I've ruled out everything else, its got a flyby wire throttle and I'm certain its working fine. Noteworthy at this point, THE CAR STILL DRIVES AND BOOSTS FINE, I've seen no drop in power, boost pressure or throttle response/lag. Just the idle is f**ked.

I took it to Nissan today and they did a full check including throttle position relearn, idle air volume relearn etc. and confirmed that it was an air leak in the intake manifold. They sprayed carb cleaner around cyl 2 and the idle dropped and misfired, again confirming the vacuum leak @ that point.

I stripped down the entire intake side of the motor including fuel rail and injectors.

This is what I found o-ring wise:

(note the bottom right o-ring - the worst of them all was in cyl 2's intake runner.) (click the pics for larger)

I've got WRX 440cc injectors in, and I installed them some 5 weeks ago, using the stock o-rings, as they are essentially a perfect fit, and the idle problem only came up once every few days, most times it would idle perfectly. However if I just let off the throttle when at high revs, or rev the car in neutral the idle would disappear and it would rev straight to 3k. I had to 'guide' the revs down in gear until i was at like 800 rpm and clutch out, then it would idle fine...

My question is, are the bad O-rings enough to cause a substantial vacuum leak and subsequent idle problem? And why did it not surface until almost 4 weeks after I installed the injectors?

What everyone's thoughts??

thanks.

Cam.

[ali-turko]

did you lube the orings up before fitting?? look like they got shredded while fitting

[StealthX]

nah i didnt. im an idiot i know i shouldve

[ali-turko]

use some Vaseline on a new set of orings and try again

[SECURITY]

or fresh engine oil.

[StealthX]

thanks ill try that when i get the new o-rings tomorro.

but can anyone confirm that this o-ring would in fact be the cause?

or am i just on a wild goose chase here?

[stealth-ish]

could be, replace the rings and see how you go from there.

just make sure all the hoses are put back firmly in the correct spot if you take the manifold or any other pieces off when replacing the rings.

[sonoramicommando]

those o rings look bad - are they injector/fuel rail o rings? that would cause fuel leak there rather than air leak.

if you haven't looked, check out injector/manifold rubber insulators - it pays to buy new ones, cos i had the same problem, massive leaks at #2, 3 & 5 cylinder.

[boostn0199]

Was the car running rough? cause when the injectors orings wearnt done right ull find it really running rough on idle

[StealthX]

Was the car running rough?

my car is MAP sensored, so when there's a vacuum leak, instead of running rough like MAF cars, is senses the vac leak like an open throttle, and raises the revs - but if my car was MAF sensored now, i would be idling rough id imagine...

those o rings look bad - are they injector/fuel rail o rings? that would cause fuel leak there rather than air leak.

if you haven't looked, check out injector/manifold rubber insulators - it pays to buy new ones, cos i had the same problem, massive leaks at #2, 3 & 5 cylinder.

those o-rings were the ones going into the manifold, not into the fuel rail.

new o-rings today... hopefully problem solved.

[Beer Baron]

well regardless of whether or not the o-rings are the source of your problem they 100% need to be replaced so do that first. stick with a set of new genuine ones providing of course they are the right size for your wrx injectors. i would say it should fix your problem, but if it doesn't you'll have to keep hunting. nothing lost though cause those o-rings needed replacing regardless.

[StealthX]

Yeh good call Rich.

Admittedly, I skimped out a bit when doing those injectors the first time, so I've only got myself to blame i guess...

New o-rings are here, update in an hour or so.

[StealthX]

No good new guys. I've installed the new o-rings, and STILL no luck.

On first start-up, it was ok... idled fine, normal cold start, but after a minute or so, the revs started to rise, back up to 3000 rpm and now im no further forward.

Its got me completely stumped. Just gonna take it into Hyperdrive (the performance shop) tomorrow and let them have a look at it...