The AUSubaru.com.au Forums

Ok so I had the car worked on a couple of weeks ago by some mechanics trying to reduce fuel consumption and sluggishness at speed. They put it on the dyno and worked out it was waaaaay rich in 3rd & 4th because the air flow meter was apparently reading higher voltage than it should. They played around and fixed that.

Now when I start the car from cool or warm or hot (more than 5 mins off) it idles really low and will sometimes stall. It also bogs badly if I try to accelerate at and normal rate and only recovers when the revs get up a bit and the turbo comes on. It also bogs a bit when it's cold cold. All is good after a minute or so.

I've tried a bunch of things
- Timing doesn't make a difference
- cleaned AAV (on top of thermostat) with carby cleaner
- pinching fuel lines doesn't seem to help
- pulled 2 plugs out at a time and cleaned to see if there was fuel leaking from injector - no difference (but the one closest to the dizzy was particularly clackety)
- revving it doesn't help
- turning up idle screw doesn't help

- AAV seems to take a long time to open on the cooling cycle - several hours - and only opens partially anyway
- I don't know what the mixture is doing for this first minute after start so maybe something's out there
- dodgy injector?

Anyone got any good suggestions?

More...

Fuel line feels a bit squishy when engine off compared to running, supporting the leaky injector theory.

I don't have the correct socket to get the CTS out - is that in the coolant like the thermostat?

Coolant Temp Sensor is in the coolant just like gauge sensor. Fast idle comes from air bypassing in that ontop of thermostat unit - checked hoses both ends of it ?

I'd take it back to the same dudes especially if it wasn't doing this before . But then again, I wouldn't take my cars anywhere .....

Ok I changed the cts tonight so I'll see if that helps at all. A quick test suggests not...

I think it's either an injector pissing out fuel or a bad pump as I'm losing about 90% of fuel line and return line pressure within about 5 mins of shutting off the engine. I took all the injectors out last week and didn't find any issues with leakage or anything (not that I had a great testing method - big syringe plugged into the fuel hose adaptor thing).

I think this explains why it's running so bad on a warm start but is fine after a couple of minutes when the pressure has built up.

What did they do to fix the air flow meter?
Hotwire or flapper?
The AAC sometimes needs to be adjusted (getting old now), from cold what RPM does it go to?
Are all plug contacts clean and shiny, if not clean them.
Fuel pressure dropping down can be the pump, its not a new car.
If its an injector, it would run rough on that cylinder.

I'm not sure exactly, they said it was reading higher voltage than it should.
Flapper.
1300 ish.
Yes.
I'm leaning towards the pump, but can't rule out leaking injector, although it doesn't run overly rough

How can you adjust the AAC? It looks fairly sealed to me

AAC now, or AAV ? typo

that thing on the thermostat housing is one of two things that usually get damaged in transit as a used import engine and can split open if you try I think.

From experience and your description, don't think it is that valve. I deactivated mine due to the brittle hose between it and manifold, for a short time - it gave no drive issues, just bit like driving with a choke start on a carby. Then went LPG, so disconnected it. Swap back to petrol for diagnostics andthe AA whatever never gave trouble. I also run the later fast idle control device FICD think they are, disconnected on my Vortex, very not noticeable any start up temp!

Tried diagnostic process with ecu and its coloured plugs?

Take your fuel injectors and have them cleaned and flow tested, made a huge difference to mine. Squirting not spraying fuel, made the car feel like it was running lean, even though afr gauge was showing way rich.

Usually the problem with adjusting the AFM is that it changes the voltage throughout the whole range

I took the cheap preview option and got a bottle of chevron 5000 and within 30kms it's back to normal - that's some super effective gear! Saved the $200-odd bucks to get it done by the pros.

top marks to our diagnostic technician Gannon !

Ok so with no real improvement with the injector cleaner (might have been a bit but not as much as needed), I bought a fuel pressure gauge.

On starting, pressure immediately went to 32psi (from 0).
Low/rough idle still present.

On revving, pressure went to 38-40 then back to 32.

When I removed the vac hose from the regulator, pressure went to 38-40 and stayed there even when revved.

On switching off, pressure immediately dropped to about 20psi then to 0psi within 1 more second.

So, geniuses, what the hell is going on!

Pressure is low - should be 36psi? - dodgy reg/weak pump?

Where is the pressure going when I switch off? - can't be an injector leak. So that would leave the reg or the pump, right? Is there a check valve or anything on/in the pump that could be allowing flow back?

And I went for a drive with the gauge strapped to the windscreen and saw...

Slow speed for gear (eg 3rd at 30) pressure flapping (fast) between 25 and 43psi before flattening out at 36ish under load.

Under full boost (7psi) fuel pressure about 43psi.

Under decelleration and gentle acceleration, 30psi, very stable.

And got the wifey to help so I could clamp the lines on shutdown and...

Clamping the supply line after the filter held pressure - that means the pump is stopping flow properly.

Clamping the return line after the reg did the same thing, so the injectors are ok but suggests the reg isn't holding pressure on shutdown.

Funny thing happened after that... The system started holding pressure at 25psi - wtf?!

The low idle seemed not to be such an issue after the residual pressure returned.

So does that mean we're back at the reg being the problem? Are the pressures I've listed (30/40/25) actually problematic?

Funny how you normally don't go testing something that ain't broke, so don't see proper measures. I found my GLTA's fuel pump was fine stationary, only dropped when asking for power and saw it drop off the 36psi mark to about 10 psi. So, new pump went in, no problems, never needed to check it again.

Sounds like the pumps check valve or whatever it is that holds pressure inline for next start is failing, and by your wife clamping the line may have rested the valve, allowing it to work a bit better - just don't write it off as beginners luck

Or, it is the preesure reg.

Take your pick. A new fuel pump and clean tank would not hurt for reliabilities sake.

The only fpr fails I have seen, get fuel out of the vac hose.....

I replaced the fuel pressure reg on my EA82T. Couldnt get a subaru one, but a Nissan N13 Pulsar fuel pressure is the same pressure spec as the factory EA82T one.

Lines are slightly different, but not hard to make it fit with a little extra fuel hose

What n13 engine is the fpr from?

I dunno, but it looked like this


I know i got something from this mob, so it could have been this
www.injectacarb.com.au/fuel-pressure-re ... san-pulsar

Cheers, I also want to try a different aux air valve, are there any options for them or is genuine the only way?

before replacing aux air valve try disconnecting its air hoses. sca and others do rare spares water blank off plugs. half inch ones fit to cap off at manifold in and aux air out....