fuel pressure regulator vacuum diagram..

[blue62]

Originally Posted by Starter986

Blue... question...

Would having a Durametric at one's disposal eliminate a lot of "chasing"? I'm halfway familiar with the product, have never used it, but I believe you can see in the app the fuel pressure... bad connections... etc. No?

I ask because I've been considering the enthusiast version. I'm still working on a fuel smell... and that darned P0455 popped again. I've been unable to crawl under the car due to a bad back.

Thank you.

What JFP said..
Additionally diagnostic tools are great to have.
BUT you need understand the system,part, sensor, circuit that your testing and it's relationship to the other systems, sensors,parts, and circuits.
You also need a good diagnostic procedure... otherwise any diagnostic equipment will just give you another way to chase your tail.

[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.

[jaimster]

Originally Posted by 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.

Great ! thanks for explaining that to me Blue62.

now I have to determine which wires on the MAF connectors are what ?? voltage , ground , signal and so on .. thought I was looking at bad MAF sensor dud...lol

got some homework to do on that is almost 6pm here in dfw tx I do still want to DO a SMOKE TEST tonight just for my own curiosity ..i will be looking at all possibilities.

intake ( under there have a borescope camera I can use to look underneath ) exhaust . oil tube .
oil cap , gas cap /..

thanks again to All.

update : got another smoke test done with cold engine - looked all over the car exhaust AOS which maybe leaking at the very botton connection NO SMOKE at all

however FOUND the oil dipstick tube leaking right under transition in between the trunk ( hard to get to ) .. NOT sure how I missed it a while back maybe cause I did it with a hot engine

I m going to try to fix it tomorrow wrapp special insulation tape around it and glue /adhesive all over area - it has worked on some other hoses i have done well SEE ..i will do a smoke test the next day ..

[jaimster]

how could I missed it - it was there right under my eyes !!!

the oil filler tube connection under the firewall through the trunk - DID another smoke test after reinstalling the oil dipstick tube ( may or may not have been the culprit after all ) .

oil filler connection broken leaking real bad - just order one from ebay I m pretty sure that has been one of tghe biggest ISSUE all this time NOT the only one thought

vacuum system was all broken all good now ..

thank you very much specially to BLUE62

[blue62]

Originally Posted by jaimster

how could I missed it - it was there right under my eyes !!!

the oil filler tube connection under the firewall through the trunk - DID another smoke test after reinstalling the oil dipstick tube ( may or may not have been the culprit after all ) .

oil filler connection broken leaking real bad - just order one from ebay I m pretty sure that has been one of tghe biggest ISSUE all this time NOT the only one thought

vacuum system was all broken all good now ..

thank you very much specially to BLUE62

Sounds like your starting to get things sorted out.
Vacuum leaks can be pain to track down on these cars.
Everything is under vacuum including the crankcase which is usually under slight pressure on most engines.
When you get the oil fill tube replaced let us know if that fixes the problems.

[Gilles]

Since you will be replacing the oil filler tube, I would suggest to replace the accordion hose that goes from the bottom of the AOS to the top of the engine (driver side) as these plastic hoses are 20+ years old and get very brittle with age and heat.
To replace this hose you don't have to remove the intake plenum, as you can get to it from the engine cover behind the driver seat.