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Discussion Starter #1
How's it going everyone? I'm working with a 99 SAAB 9 5 2.3t 5 speed standard transmission. I bought it used and it's got 139k. I know the PO has done maintenance on it because it actually runs great and I believe I'm only the 3rd owner. Well when messing around with the SID one day I noticed it said I was getting 13 MPG. After some city driving today it went all the way down to 10 and is now sitting at 11.5 MPG. Is there any way this is correct? Now I do have one CEL code - P0455 which I'm guessing could definitely be related. I'm planning on ordering new spark plugs and hopefully I don't need to order the CID, as well as fuel filter, fuel pump, air filter, PVC update kit, gas cap, and GFB DV+. Soon I would also like to replace the turbo with a TD04 and get a upgraded radiator and intercooler as well as a ecu tune when I get all the maintenance taken care of. I'm considering replacing the coolant bypass valve but I just learned about the Euro spec heater hoses that replace it and am thinking that sounds like a way more economical option. Anyway does anyone have any ideas what else this could be caused by?

EDIT: I figure I should mention as well that the P0455 code comes and goes... It was there a couple days ago but has been gone for the last day and a half
 

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That mileage is awful...our 2009 Suburban doesn't even get that bad of mileage, lol. What kind of driving are you doing? Are you calculating your MPGs manually, or relying on the SID readout? How many miles are you getting per tank, roughly? I doubt that P0455 code could cause that poor of mileage. I took mine on a road trip today and was getting 30 highway. My overall average is around 22-24 MPG with mixed driving. No way it should be as low as what you're seeing, unless you're driving in some really extreme stop and go conditions.
 

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I have a 2004 - the MPG suddenly dropped and the problem turned out to be the o-ring around the top of the throttle body. These deform and flatten, and can even roll out of the groove. New o-ring - back to normal. Vaseline it as you slide the charge pipe elbow on.

20200604_171600.jpg


P0455 leak could be anywhere, but the NRVs in the engine bay are the gatekeepers as far as the engine is concerned, and the blue ones fail open. I found mine near the power steer res. had done so, but I didn't perceive any performance or fuel consumption change with it failed. The consequence is that when on boost, air will leak out of the TB back into the evaporator system, but when not boosting, it just tries to suck towards the TB which is its normal mode. The result would depend on whether the other blue evap. NRV is also failed open.

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I can't recall whether I actually got P0455 with the NRV failure. I found it by inspection, sucking/blowing the valves. Also the 'T' joint near the cobra had split as well, also a common fail on these. I modified to the 2005 evap. system.

Whats a GFB DV+ ?

Plugs - only get the NGKs specified in your owners' manual. They are tuned to the SEM/NGK DIC and any other brand (of plugs or DIC) will run, but badly.
 

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Hit CLEAR on the SID until it beeps and says CLEARED and drive for a bit, checking estimated range and MPG. Make sure you have set it to US units (hold CLEAR and SET simultaneously to choose language and units).

Also compare SID estimate with actual economy. I find that SID is normally very accurate (within a few percent, which is close enough). There could be some issue with the SID or its configuration. You'd need a Tech II to investigate further.
 

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Discussion Starter #5
That mileage is awful...our 2009 Suburban doesn't even get that bad of mileage, lol. What kind of driving are you doing? Are you calculating your MPGs manually, or relying on the SID readout? How many miles are you getting per tank, roughly? I doubt that P0455 code could cause that poor of mileage. I took mine on a road trip today and was getting 30 highway. My overall average is around 22-24 MPG with mixed driving. No way it should be as low as what you're seeing, unless you're driving in some really extreme stop and go conditions.
alot of stop and go and sometimes highway.. it really depends. im in phoenix and theyre doing alot of highway construction right now so ive been on the surface streets alot more.
 

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Discussion Starter #6
I have a 2004 - the MPG suddenly dropped and the problem turned out to be the o-ring around the top of the throttle body. These deform and flatten, and can even roll out of the groove. New o-ring - back to normal. Vaseline it as you slide the charge pipe elbow on.

View attachment 274604

P0455 leak could be anywhere, but the NRVs in the engine bay are the gatekeepers as far as the engine is concerned, and the blue ones fail open. I found mine near the power steer res. had done so, but I didn't perceive any performance or fuel consumption change with it failed. The consequence is that when on boost, air will leak out of the TB back into the evaporator system, but when not boosting, it just tries to suck towards the TB which is its normal mode. The result would depend on whether the other blue evap. NRV is also failed open.

View attachment 274605

I can't recall whether I actually got P0455 with the NRV failure. I found it by inspection, sucking/blowing the valves. Also the 'T' joint near the cobra had split as well, also a common fail on these. I modified to the 2005 evap. system.

Whats a GFB DV+ ?

Plugs - only get the NGKs specified in your owners' manual. They are tuned to the SEM/NGK DIC and any other brand (of plugs or DIC) will run, but badly.
Thank you for reminding me, im actually going to go and put those on right now. I did happen to order the o-rings for both sides of the throttle body!

What are the NRVs if you dont mind me asking?

Also I have noticed it seems as if i have a power steering leak by the reservoir, but i dont know if that might be an intentional feature because i notice there is a little hole in the cap. Although i suspect thats not relatable to what youre talking about right?

GFB DV+ is Go Fast Bits brand DV+ (diverter valve +). Its supposed to have faster actuation and be better than the OEM Bosch unit because its not only 0-100%... Meaning the DV+ can open partially and close partially when less air is moving.

Lastly I did buy NGK 7 heat range 11 gap spark plugs which i believe might be for the V6 model but i have seen it recommended for a car with power upgrades. I have yet to bump up the torque or HP but i plan on it soon with a tune, TD04HL turbo upgrade and the King Cobra TIP. As well as other support mods: aluminum intercooler and perhaps radiator, silicone vacuum hoses, 3" turboback exhaust, fuel pump and injectors. Im still unsure of whether i should just stick with the normal TD04HL-15t or go all out and get a TD04HL-20t 7cm turbo. I just need to figure out if it will fit in the stock location and whether i need dioffoerent flanges or anything to make it fit.
 
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