Hissing from below the intake manifold after shut off
 

Alright...so some of you may have seen my thread in the fuel section...but Im having problems of going 1-1.5 points lean during WOT. I've no joke tried everything from MAF sensor swaps, switch back to stock tune, swap O2 sensors, checked intake clamps ect.

Anywho, my fuel PSI is perfect (1600-1800 psi), so my only other guess would be that my injectors/fuel rail is having problems.

Anywho THE POINT OF THIS POST...

every now and then about 30 seconds after I shut my car off I will get a hissing noise that seems to come from below the intake manifold (fuel rail area).

Its not the sounds the ECU makes after shut off...its about 10-15 seconds after the ECU noises stop...and it comes from directly below the Intake Manifold.

Is this normal? Have others have this hissing sound happen?

Have you donated to the site yet?

blown injector seals? something is leaking pressure making the hissing sound, so its possible its the fuel rail or injectors which would explain the lean afr's since fuel/pressure is leaking out somewhere...

AF, i know your convinced there isn't a problem with fuel pressure, and while that may be correct, everything you describe screams fuel problems. Just like a car with boost leaks can still achieve the target boost, a fuel rail with a fuel leak can still report the proper pressure.

I bet your on to something with this hissing. Time to pull the mani and the injectors and take a look.

just wondering, where is fuel pressure measured?

on the passenger side of the fuel rail.

I agree with you 100% that its pointing at fuel problem. Its either not enough fuel, or to much/unaccounted for air. And the MAF sensor is fine, there are no pre turbo leaks, O2 sensors are fine, its not the tune, and Im using the HPFP from my old motor which worked great. Its just baffling since FP seems to hold just fine.

I know PTP was talking about the fuel rail holes to the injectors being small. Well since the pressure sensor is in the fuel rail passenger side...theoretically there could be a small leak AFTER the small hole, which would loose pressure there, but since the hole is small the pressure could hold and seem to be unaffected in the actual rail area.

I have my old fuel rail and injectors from the blown motor. I already ripped out my old injectors from my old head...and Im really leaning towards swapping out the fuel rail and injectors with my old ones.

I have a hissing noise that occurs after the cars shuts off. Takes around 3-5 mins for the noise to occur after turning it off. Never thought anything about it.

This might sound dumb, but you might check to see if its your engine coolant making noises due to convection in the head.

injector stuck open?

does it take a few seconds to start it sometimes ? like its burning fuel thats been dumped before starting

I have also noticed this

Yea...i thought about the coolant possibly being the reason for the hissing...but it comes from right below the intake manifold. There shouldnt be any hissing for coolant coming from that area...hmm maybe the noise is normal.

Car starts up fine eveyr time.

In the head there is a coolant path that runs the length of the head just under the intake ports.

The TB also has coolant.

When coolant is unevenly heating and cooling in a hot engine that is turned off it can make a hissing sound.

The way to rule this out is to start and then kill the engine while it is cool and see if it hisses.

Rog...ill try that tomorrow

i dunno but since last few months seems like i been having all the same problems you have been ... and me its injectors

good luck with that man

wait did u say you found the problem and its the injectors?

maybe im misplacing you with someone else , but i think i remember you saying you had fuel trim problems . way too negative or something. and some other things you mentioned before i remember saying to myself fuck mine does that too....

everytime i got a probleme seems like someone else gets it at the same time as me ,.. anyway,..


new injectors will probly cure my car from running like shit in general ... i made a post earlier , just look a few posts ahead or below ... called injector stuck open

anywya , good luck again , i hope im getting some this time .. but im pretty posotive its gonna run well soon ... but for how long , dunno

let us know when you find out more ,,,

i cant help you since everything i know on this car i pretty much learned from youz on here...

Well Im pretty stumped. Ive messed with basicly everything except the fuel rail/injectors...so Im just trying to gather some more info on swapping out injectors.

Apparently someone said I have to replace the seals...