1996 Geo Tracker Check Engine Light

[sina27]

Hello,

Got a 96 Tracker 2WD 5 speed. 
The check engine light turned on the other day, and I hooked up my Bosch OBD2 reader and got these codes:

P0171
P0443

Online forums said that the codes mean:
P0171 ( Fuel System Too Lean)
P0443:  EVAP I System Improper Purge Flow

Any ideas on what the underlying cause is, and if they are related? How to fix? 

Thank You

[sina27]

I'm thinking its my EVAP purge valve? (EVAP VSV).
I disconnected the hoses and wire, ans tried blowing air through it. Air passed through it freely with everything disconnected. This would mean it is bad, correct?
I'm having trouble finding a replacement EVAP VSV online. Any recommendations on where to get one? When I search autozone or RockAuto, I'm not seeing the correct part....

[fixkick]

the gas cap loose does that soeasy, or many other things, even a cracked vent hose. bad cap, loose cap, wrong cap, gee caps are cheap and every cheaper is tighten it , reset the ECU DTC and see it go away, doing the evap 1, leakdown tests on my page is not easy at all. lacking special test cap. to do that , (the regulator near tank could stick open)
and see if it goes away, cap now tight.
It could means the fuel tank will NOT hold pressure about 1/2PSI, ever hear a gas cap pulled off do that whoosh sound on hot day? bingo evap pressure. NORMAL. The cap correct has a vacuum breaker in it SO VACUUM neverhappen here ever.

but to be sure lots of ways for this to fail. sure ! do you smell gas fumes ever? be first. to mention.

the more important are 171s. lean This means the fuel trim has slammed and stuck on lean.
bad O2 sensor , or low fuel pressure, or dirty maf. (just need cleaning) type MAF on my page.
does car drive ok?, all the time, hot and cold and for sure flogged up hills?
id for sure fix 171 first. lean can burn exhaust valves up.

[fixkick]

443 is purge valve test but is dumb as brick
the tank must hold pressure so any purge test one must
check pressure first. and if good then open the purge and see it drop
if no drop fails.
my guess is that it sees either of 2 pressure test wrong, 433 fails.
there is gross fail test DTC too.  I think 433 is minor leak.  like  loose cap, would do.    this is all tricky FIRMWARE testing in the ECU.  poorly documented.

im going to look on 96 chapter 4 for 443 details now.
page 10 here
part 4 here,  443 section , and below the PDF below is 2nd coverage on this EVAP2 system.
http://ge.tt/6gvplbp2

the steps is does to do the actual test is not stated clearly at all, only the most vague.
but the tests are good. in the test logic table there.
the whole thing is here. suz 96


https://fixkick.com/sensors/EVAP/EVAP96.pdf

[sina27]

Thanks Fix Kick,

I cleared the error codes. The other day when driving for a while, I turned off the car and removed the gas cap and heard the "whoosh", so thats a good sign. 
The error codes have not turned back on (I've driven the car over 50 miles since....how long before the car recognizes the error again?)
For the valve purge test outlined in the manual - I removed the hoses and the connector, and I tried blowing air into one of the nipples (the one that connects to the evap cannister). Air was able to go through the valve purge. This means that it is faulty, correct? With the connector and hoses disconnected, the manual states I should not be able to blow through it.
Using a multi-meter, the resistance measured @ 35 ohms, which is within range.
I'll go ahead an order a valve purge unit just to be on the safe side.

[fixkick]

great, but it can take 3 driving cycles for some DTC to  set.  (OBD2 is very tricky rules and only reading the first PDF above, shows  this.
if you blow into the can hose, it is free air vented.  the can has 3 holes, 1: vent, vacuum to VSV and one hose to the take via regulator.
also the VSV valves are defaulted to open (with key off, so only key on 12vdc there are closed yes tricky but all VSV on this car work backwards key off.
id wait to see if it fails with tight cap or new cap on tank.  there are like 50 test to check the whole system ,  leaks, many, valves 3,  vacuum hoses bad, pressure sensor bad, tank rusted through the top center tank has plastic silly vapor baffle 6ghttp://ge.tt/6gvplbp2/v/17vplbp2box  that can crack.  the list is huge, for leaks, in shop or any smog station test 1 in with special cap with a hose fitting on it.
then they do a leak down test in 5min work if that passes then there are no tank leaks or vents leaking in the rear, all  in 5 mins work , leaving all the easy stuff up front to  test, 1 by 1.

SEE HERE I TOOK THE PDF ABOVE AND CUT THE PHOTO OUT OF IT AND ADDED RED HOSE LETTERS
which hose did you blow? on.
the tank pressure test proves all is ok from E to the right side,  all in 1 test. the 1/2 PSI pressure leak down test it is called if fails we hold that pressure with shop air and1/2 psi paint regulator (shops use nitrogin gas) and use spray bottle and find where the vents leak, bubble test. just like finding heater natural gas leaks. same deal.

when car starts and moves down there road, valve 7 opens. letting vacuum  can-tank #4
and valve 11 opens to let in fresh air, so that fresh air, lets the canister, flood with clear  fresh air and engine sucks all gasoline fumes and burns them.
engine off, ,both those 2 valves above are closed, preventing fumes, from leaving the CANISTER as you sleep, etc.

all other parts there electric are self tests DTC tests.  like 443 . valve 9 is a 3 way valve,  i think it can artificially open regulator #2 and it  opens. E to B/
valve 9 i think, at its bottom arrow, means vent port.
if a filter is seen there,that vent port. and normally D pipe goes to vent making the regulator work at 1/2psi.

 

[sina27]

Thanks for the reply. 
So for the VSV (evap can purge valve, diagram 7 on the image you posted) - with the car off and connector unplugged from 7, the FSM says to diagnose it you blow on hose D (hoses F and D are connected to the purge valve, but disconnected from throttle body / cannister). The FSM says that with 7 disconnected and the car off, I should not be able to blow air through hose D, since the purge valve is closed. It says it opens when you apply voltage to it. 
When I tested this, I was able to blow air through it with it disconnected - which means the purge valve is bad, yes? 
 However you mentioned that the valve is supposed to "defaulted to open with key off". Is the FSM wrong? Or by "open" do you mean I shouldnt be able to blow air through it? 

Additionally, I think the diagram you posted is for the enhanced EVAP. I don't think I have enhanced EVAP, just the regular EVAP. Would this make a difference?

Below is an image of how I tried diagnosing #7 you listed, the evap purge valve vsv




https://imgur.com/a/aHFpInE

[sina27]

after clearing the check engine light and driving for some time, the light came back on only this time I got the p0171 (engine lean) code and not the p0443; 
does this mean my evap VSV is okay? Or can both codes be caused by a bad evap VSV? what about a bad gas cap? 
Womdering if I should order a new evap vsv...

[fixkick]

after clearing the check engine light and driving for some time, the light came back on only this time I got the p0171 (engine lean) code and not the p0443; 
does this mean my evap VSV is okay? Or can both codes be caused by a bad evap VSV? what about a bad gas cap? 
Womdering if I should order a new evap vsv...

keep in mind the EVAP test does not run on a full tank of fuel.
it needs air  space above the fuel level in tank to be accurate,
evap system testing is NOT EASY,  but leaks tests are always first or cleaning and bench testing all VSV valves to is easy.
VSV is just  air valve, vacuum.   electro solenoid air valve but designed for vacuum.  and some work backwards from basic thinking,  ... type vsv in my main page, see lots of testing examples.

171  is lean code.
does the engine ACT lean?  that is first,  post all things the engine does good and bad or  ugly,   all things matter in diagnosis, (evidence matters big time) all.