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System Too Lean. Pls Help

J

jca1980

CEG'er
Joined
Jun 3, 2005
Messages
35
Location
Kelowna, BC, Canada
CEL CODES:
0171: System to lean bank 1
0174: System to lean bank 2
1131: Lack of upstream heated oxygen sensor switch. Sensor indicates lean bank 1
1151: Lack of upstream heated oxygen sensor switch. Sensor indicates lean bank 2

HISTORY:
For a long time Bank 1 was acting up causing the CEL to come on. But the car ran "OK"
At some point in the fall Bank 2 joined the party.

SYMPTOMS:
Really bad fuel efficiency. (approx 350km/tank)
Loss HP/Torque (really noticed in the hills)
Occasional drop in idle.
Very occasional stall.


PREFORMED MAINTENANCE:
Replaced the fuel filter in the fall.
Vacuum tested ERG valve in the fall. (Passed test)


From what I have read in the forums its is likely a Vacuum Leak.
I'm gonna go pick up some cleaner and see if I find a leak. Though at this point I'm not sure where I should start looking for the Leak. On the passenger side of the engine bay I can hear what I think sounds like air flow (near the belt so its hard to be certain).

Also I have picked up two O2 sensors (Bosch pt#13115)

Any pointers or help is very much appreciated.
I am aware of the BANK 1 O2 "How To".

Thanks Guys (and Gals?)
 
Cleaned MAF with pipe cleaners and contact cleaner. Reset CEL with reader. Car still runs rough.

UGH. I guess I will change out the O2 sensors tomrrow morning.

Any ideas ppl?
 
Don't change the O2 sensors. You will be wasting your money. You have a massive vacuum leak. The carb cleaner won't help. What year, tranny and how many miles on the car?

jca1980 said:
.... On the passenger side of the engine bay I can hear what I think sounds like air flow (near the belt so its hard to be certain).
......
Click to expand...

Look for a broken rubber or plastic hose. As you have reset the PCM, wait for the new CEL to come on, scan it and post the code(s).
 
Last edited:
Thanks for the reply Tony,

The car is a '98 Mystique LS MTX with 127,000km.

Just a general visual inspection didn't reveal anything to me but then again, its kinda hard since I don't really know what I'm looking for. The codes i posted at the beginning of this thread, where pulled this morning prior to me starting to work on it. I will repost codes as they reappear.

Any advice on how to better locate this leak?
 
jca1980 said:
Thanks for the reply Tony,

The car is a '98 Mystique LS MTX with 127,000km.

Just a general visual inspection didn't reveal anything to me but then again, its kinda hard since I don't really know what I'm looking for. The codes i posted at the beginning of this thread, where pulled this morning prior to me starting to work on it. I will repost codes as they reappear.

Any advice on how to better locate this leak?
Click to expand...
Okay. It appears to be an exhaust or manifold leak from the underside. Drive up Rhino Ramps or jack up the car and put on jack stands. Then go under and "feel" (not the metal) for air coming out or listen for air going in. It is probably near the O2 sensors or PCV valve. Note that I once had an "air sound" at the bottom due to a broken (in half) lower O2 sensor. However, that also gave a O2 sensor circuit code.
 
OK the CEL is back ON.

0171: System to lean bank 1
0174: System to lean bank 2
1131: Lack of upstream heated oxygen sensor switch. Sensor indicates lean bank 1
 
eepals said:
At your mileage it would not hurt to clean out the carbon/gunk in the lower intake and replace the LIM and UIM gaskets. Read this article.

http://www.motor.com/MAGAZINE/Pdf/042003_09.pdf
Click to expand...

Is it a hard job to perform the above mentioned work? I have ramps jacks stands and most common hand tools and some less common. Are specialty tools required? I'm at work right now but when I get home i will search for some "how-to"s. I lack vehicle specific maintenance/repair experience. But I quite mechanically inclined.

You help is much appriciated.

I'm just about ready to give up and send the car to the dealer.. My last tank of gas lasted 320km.
 
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