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P0174 - system too lean bank 2

8

8000RPM

CEG'er
Joined
Jun 21, 2005
Messages
328
Location
Washington, D.C.
So I have lost some power and when I accelerate hard from 60mph to 80mph there is this smell coming inside of the cabin. About 2 months ago I got a MIL P0174 - I reset it and it never came back. This morning I took out my sparkplugs, checked the gap and re gapped them to 0.05. Checked the resistance of the wires and they all seemed to be fine. When I cranked the engine I got a MIL again...same code - P0174.
I am about to clean the MAF, oil my K&N filter and add injector cleaner in the gas tank before I fill it up...what else should I check? All my EGR vac hoses seem to be fine, the throttle body is clean, can't find any cracked hoses... :((

i also noticed that there is some oil coming from the vac hoses that go from the air duct into the valve covers (I think they are called valve cover ventilation hoses). I haven't had that before. Is this normal?

I am lost at this point. Any suggestion will be welcome.

its a 98 E0 SVT Contour. I have homemade MIL eliminators and the upstream 02 sensors should be good...changed them about 20k miles ago. Car currently has 123k miles...
 
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When I started to get lean on only one bank the fix was replacing the seals between the fuel rail and the intake. I replaced all the seals because it's a 2 hour job. There are O-rings where the vacuum lines go into the top of the intake that dry out and disappear too.
Dirty MAF will throw off both banks at once.
How much oil is coming from the crankcase breather? Too much means the rings are worn allowing a lot of blowby. Check the PCV system - valve and the hose it sets in to be sure it is drawing a vacuum on the engine. Otherwise the vapors will go out the inlet side before the throttle plate instead of the intake manifold side via the PCV valve.
Outside chance on a code PO174 is an O2 sensor. I get rid of the sensors after 50-60k miles because they effect the gas mileage and power quite a bit. You will need and scanner to test them. At your cars age I would get rid of both of them.
Warning, don't used too much injector cleaner or too often because it will eat up the coils in the injectors. I've replaced 3 injectors due to bad coils.
BTW, a lean engine will produce a foul odor from the cat converter!
 
maybe one of your MIL eliminators is bad, the 02 sensor could be bad or the DPFE sensor can be bad.
 
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well i changed the bank 2 upstream 02 sensor when the car had about 85k miles and the bank 1 upstream 02 sensor when I had like 110k miles. I used bosh sensors from auto zone.

The gasket between the fuel rail and the intake..if we are talking about the same gasket, i changed that when I was cleaning the upper and lower intake manifolds. I changed all gaskets and the o-rings on the injectors. then i also changed the pcv valve. that was like 6 months ago. what are the chances that the pcv valve will go bad? (i got also got it from auto zone). The DPFE sensor i changed about a year ago, along with the egr valve. But wouldn't the DPFE sensor affect the entire engine and not just a single bank?

The smell?? well i can't describe it. smells bad. not like evaporating coolant, exhaust gases, or gasoline...it could be what someone described as smell coming from the cats...i can't tell.

there isn't too much oil coming from the crankcase breather...before it used to have no oil at all. it was really dry. now it is oily just a bit. maybe there are 2-3 sqare inches of oily area inside the air duct. hmmm i don't know what to think. I will check on that pcv valve again. it is really cheap (like $3) so i might as well change it. DPFE is expensive though...
 
A lean code means you have an air or vacuum leak somewhere between the MAF and cylinder head. The PCM is reading the combustion via the O2 sensor(s) and reporting that there's too much air vs. how much fuel it's metering.

Seeing as how it's telling you which bank it is, start looking there. However, my experience is that it could be either bank depending on how accurate/new your O2's are. Better yet, tap in to the OBD port under the dash and check your long & short term fuel trim readings. That will tell you for certain what's up.
 
8000RPM said:
.. DPFE is expensive though...
Click to expand...
Used one is $25 shipped. But I don't think that is the problem. Look for a vacuum leak first. Try and get a second opinion on the smell. Get a friend to drive with you.
http://www.contour.org/ceg-vb/showthread.php?t=21881

Per TSB, some of the causes of P0171 and P0174,

P0171 - System Too Lean (Bank 1) The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The code is set when the adaptive fuel tables reach a rich calibrated limit.

Fuel System:
· Contaminated fuel injectors
· Low fuel pressure or running out of fuel (fuel pump, filter, fuel supply line restrictions)
· Vapor recovery system (VMV)

Induction System:
· MAF contamination
· Air leaks between the MAF and throttle body
· Vacuum leaks
· PCV system concern
· Improperly seated engine oil dipstick

EGR System:
· Leaking gasket
· Stuck EGR valve
· Leaking diaphragm or EVR

Base Engine:
· Exhaust leaks before or near the HO2S
· Secondary air concern
Powertrain Control System:
· PCM concern

P0174 - System Too Lean (Bank 2) Same as DTC P0171, but Bank 2. See Possible Causes for DTC P0171
 
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Tony2005 said:
Used one is $25 shipped. But I don't think that is the problem. Look for a vacuum leak first.
Click to expand...

If it is a vacuum leak it will affect both banks, not just 1. But as I said already, it depends on the ability of both O2's to correctly read the oxygen content of the exhaust gases. Best method is to pull the fuel trim readings from the PCM.
 
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