SaabCentral Forums banner

1 - 11 of 11 Posts

·
Registered
Joined
·
2,584 Posts
Fuel pressure regulator perhaps? You've got opposite the problem I'm dealing with in an '02 VW Passat code: P0171 Fuel Mixture Too Lean.
 

·
Registered
Joined
·
4,293 Posts
If the plugs are fouled or have some other problem, you should get the code for a random misfire or similar before engine running rich.

FPR vacuum hose: The fuel pressure regulator uses the intake vacuum to keep the fuel pressure constant relative to the intake air pressure. If the FPR vacuum hose has a leak, the FPR will not regulate correctly, and the amount of fuel from the injectors will be off. The result can be a lean or a rich mixture, depending on intake vacuum/boost.

Front O2 sensor: The ecu detects whether the engine is running lean or rich by using the output of the front O2 sensor. The sensor measures the amount of oxygen left in the exhaust gasses after combustion. The fuel left cannot be measured directly, just the O2. Too much oxygen means the engine is running too lean, too little means it is running rich. If the O2 sensor is old or fouled and cannot detect the amount of oxygen, the ecu may THINK the engine is running too rich or too lean.

MAP sensor: The air pressure sensor is also used by the ecu to regulate the air/fuel mix, but it does not seem to fail very often. There could be a problem with the connector or the hose leading to the sensor though.

TPS: The throttle position sensor tells the ecu how far the throttle is open. Not very likely to fail, because it is a very simple device (basically a single turn potentiometer), but the connector might be loose or need cleaning, etc.

Based on all the bad vacuum hoses I have replaced on my car, I would suspect those first.
 

·
Registered
Joined
·
337 Posts
Discussion Starter #4
I was thinking vac lines too, I have not been holding boost as long as I used to, and in 2nd gear boost seems to cut back a bit then regroup before kicking me back in my seat. Its been hot as hell to tho, so this could be the simple explanation for the performance loss.

Is there a good way to test the vac lines to find leaks? soapy water? which ones are the vac llines, i got so many hoses running all over concealed places i think it will take months...

oh yeah, and this CEL code has appeared twice in the past 2 weeks now and releared itself on its own accord. Not sure what that means other than it might not always be a big enough problem to detect for the ECU.
 

·
Registered
Joined
·
21,583 Posts
PMI said:
If the plugs are fouled or have some other problem, you should get the code for a random misfire or similar before engine running rich.

FPR vacuum hose: The fuel pressure regulator uses the intake vacuum to keep the fuel pressure constant relative to the intake air pressure (2.5 bar on most turbos). If the FPR vacuum hose has a leak, the FPR will not regulate correctly, and the amount of fuel from the injectors will be off. The result can be a lean or a rich mixture, depending on intake vacuum/boost.

Front O2 sensor: The ecu detects whether the engine is running lean or rich by using the output of the front O2 sensor. The sensor measures the amount of oxygen left in the exhaust gasses after combustion. The fuel left cannot be measured directly, just the O2. Too much oxygen means the engine is running too lean, too little means it is running rich. If the O2 sensor is old or fouled and cannot detect the amount of oxygen, the ecu may THINK the engine is running too rich or too lean.

MAP sensor: The air pressure sensor is also used by the ecu to regulate the air/fuel mix, but it does not seem to fail very often. There could be a problem with the connector or the hose leading to the sensor though.

TPS: The throttle position sensor tells the ecu how far the throttle is open. Not very likely to fail, because it is a very simple device (basically a single turn potentiometer), but the connector might be loose or need cleaning, etc.

Based on all the bad vacuum hoses I have replaced on my car, I would suspect those first.
This one should be "sticky FAQed"..... to be part of the SC repair manual....
 

·
Registered
Joined
·
21,583 Posts
Squoosh! said:
What parts can trip this code? bad sensor, plug gaps ? anything else?
As a guess, remove, examine, and clean the O2 sensors..
Probably the sparking plugs should be worked on first, if not already done...
 

·
Registered
Joined
·
337 Posts
Discussion Starter #8
I do have autolite double plat plugs in there, I know a lot of you are dead set against that. Someday I will toss some NGK's in there.

I was wondering if there is a Haynes manual or the like that includes the OG9-3, not one that is exclusively NG900's. There are those 1000 changes or so between the 900 and 9-3 and I would really like a repair manual that recognizes that. I cant find one anywhere online yet.
 

·
Registered
Joined
·
2,584 Posts
Squoosh!There are those 1000 changes or so between the 900 and 9-3 and I would really like a repair manual that recognizes that. I cant find one anywhere online yet.
Egh, those thousand changes were things like courtesy wipe of the rear windshield when you put the car in reverse....:cheesy:

I don't think Haynes has come out with an exclusive manual for the OG9-3 yet. Perhaps I could suggest going to their website (www.haynes.co.uk) and shooting them an email asking if they do have one or if one is in the works, or just outright ask them to make one. I think I once heard that someone did that and they said the interest in the book just wasn't there and that the NG900 covered the basics. So shoot them an email demanding satisfaction, they won't make the book unless people show them that their is a demand.
 

·
Registered
Joined
·
337 Posts
Discussion Starter #11
laf

ha! ok I will settle for the 900 one then. I didnt realize one actually did not exist. I just figured it was hard to find =P.
 
1 - 11 of 11 Posts
Top