fuel pressure regulator vacuum diagram..

[jaimster]

Originally Posted by blue62

A few things that could cause your issue........
Bad MAF or MAF wires...and or connections.
Leaking Fuel Injectors.
Bad seal on the Oil Fill Tube Cap
Bad Fuel pressure regulator
Bad Evap Purge Valve under the intake manifold
Exhaust leak ahead of the Pre Cat 02 sensor.

right on Blue62!

I have tested the FPR good - after removing the vacuum hose pressure went up t0 60 PSI

have not replaced seal on Oil fill tube cap - did not see any smoke coming out of there on my last SMOKE TEST ..

how to test Evap purge valve ?

had the car running for almost half hour now TOO hot for smoke test - SMOKE TEST TOMORROW with engine COLD should be smoke coming out of the exhaust if there is a leak !!

so this is what I observed today after car warm up "

MAF a/c off 3.25 a/c on 4.0 g/s

while car was running disconnected MAF sensor SOMEBODY HELP ME UNDERSTAND THIS
after disconnecting MAF car hesitated a bit almost not noticeable CAR KEPT RUNNING

numbers on old BOSH sensor are 0280 218 055 986.606.125.01
0280 218 055 986.606.125.02 on new BOSH sensor only difference last 2 numbers 02

[Makrilli]

Your MAF readings are a bit on the lower side which should cause lean condition instead of rich.

There are three different revision of maf for e-gas cars, ending 00, 01 and 02.
If you change the version you need your DME flashed to match the new MAF sensor.
Or so I've heard.

With MAF unplugged your DME uses a default map which only uses O2 sensors and the throttle position to estimate amount of fuel needed.
It's not recommended to drive long distances with MAF unplugged but let's say half an hour shouldn't hurt anything.

[blue62]

Originally Posted by jaimster

right on Blue62!

I have tested the FPR good - after removing the vacuum hose pressure went up t0 60 PSI

have not replaced seal on Oil fill tube cap - did not see any smoke coming out of there on my last SMOKE TEST ..

how to test Evap purge valve ?

had the car running for almost half hour now TOO hot for smoke test - SMOKE TEST TOMORROW with engine COLD should be smoke coming out of the exhaust if there is a leak !!

so this is what I observed today after car warm up "

MAF a/c off 3.25 a/c on 4.0 g/s

while car was running disconnected MAF sensor SOMEBODY HELP ME UNDERSTAND THIS
after disconnecting MAF car hesitated a bit almost not noticeable CAR KEPT RUNNING

numbers on old BOSH sensor are 0280 218 055 986.606.125.01
0280 218 055 986.606.125.02 on new BOSH sensor only difference last 2 numbers 02

In simple terms:
The Maf sensor is two sensors in one.
It senses Intake Air Temp. and Intake Air Mass.
From those two things the DME knows how long to pulse the Fuel Injectors thus creating the correct fuel air mixture. (all other things being correct).

When you disconnect the MAF sensor the system reverts to a preset default fueling strategy. That fueling strategy is derived from a fueling Map or table that is largely driven by the parameters of engine RPM and Engine load.
So if you disconnect the MAF with the engine running it takes a second for the system to change or adapt to the default fueling strategy.
That is my current understanding of how it works.

Your looking for a "Voltage Spec." at the MAF Sensor.
Key on engine off your looking for 0.9V - 1.1V
Engine running at idle approx. 1.4V

[blue62]

Testing Evap Purge Valve for vacuum leak:

Disconnect the hose from the intake to the valve. (at the valve).
Disconnect the Electrical connection.
Apply vacuum of 0.7 bar to the valve.
Vacuum should not fall below 0.5 bar after 10 minutes.
That will tell you if it holds vacuum correctly or not.

[Makrilli]

I have a strong suspicion the new intake might have something to do with the problem, perhaps the diameter of the MAF tube is somehow smaller than stock.

I also had a problem with my boxster running rich.
It was very frustating and among other things I bought durametric, two new MAF sensors, replaced O2 sensors and checked fuel pressures.
In the end I read a forum post suggesting to check the mesh just before the MAF which seems to collect trash thanks to the bad design of stock air box.
I had small pieces of leafs stuck around the edge of said mesh impacting airflow, but not on front of the MAF so the readings were normal.

Your problem shouldn't be the same I had but disconnecting the MAF might help pinpoint the problem, even if it's not the MAF sensor itself.