Emissions Problems...

[vengeful]

OK. This is going to be lengthy, so bear with me. I've got a few problems with my truck, and need some guidance. I don't have time to go through all of the diagnosis in the FSM, especially for the O2 Sensor and EVAP codes.

 

List of Codes and Translations:

 

P0325 - Knock Sensor - An excessively high or low voltage is sent from the Knock Sensor to the ECM (I'm not worried about this one right now).

P0158 - Left Bank, Rear Heated Oxygen Sensor - The maximum voltage from the sensor is not reached to the specified voltage.

P0159 - Left Bank, Rear Heated Oxygen Sensor - It takes more time for the sensor to respond between rich and lean than specified.

P0505 - Idle Air Control Valve/Auxilliary Air Control Valve (IACV-AAC) - The IACV-AAC Valve does not operate properly (uhh...DUH!)

P1440 - Evaporative Emission Control System - Small Leak - Positive Pressure - EVAP Control System has a leak or EVAP Control System does not operate Properly.

 

What I know and Symptoms:

 

P0325 - I'm not worried about this, because I'll pass emissions with it in the ECM, and it wont effect anything with the vehicle.

 

P0158/P0159 - This one I'm kind of worried about because it has a rather expensive list of check items. Harness or connections, The sensor itself, Fuel pressure, air intake leaks, fuel injectors. I've already got a replacement sensor (aftermarket, not Nissan), and a full set of intake and top-end gaskets. I'm kind of hoping the malfunction is the Oxygen sensor itself, or an intake air leak, because then I wouldn't be out of pocket anything.

 

I know I need to replace the fuel filter. It's pretty old. However, if the fuel filter was clogged up and causing low fuel-pressure, it would affect both banks of the engine and not just the left bank. Also, at my malfunctioning IACV-AAC Valve set idle speed of 500RPM, the left side exhaust pipe vibrates. The right side is steady.

 

The list of check items for both codes is the same, which is why I put them together here. I'm wondering if there is any reason to eliminate any possible causes because of the fact that both codes are present. I didn't see anything in the FSM, though I may have overlooked it. I also do not recall any TSBs about this.

 

P0505 - The IACV-AAC valve is malfunctioning. My truck idles at about 500RPM when warm. I'm hoping that it's just gummed up and not actually broken, because then, as before, I wouldn't be out of pocket anything. The list of check items on this code is SHORT. The Valve, or the wiring. I have no reason to suspect that the wiring is to blame, but you never know. Has anyone ever had to work on their IACV? Any tips? Anything that I'm overlooking other than the Gasket.

 

P1440 - This is the one I'm worried about. This has a list of check items a mile long, ranging from a loose gas cap, to bad valves. I had to replace my Charcoal canister at about 75,000 miles because it was full of water - my fault. At that time, I did not blow out the EVAP lines or any of that. I used the old VCV and all of that stuff.

 

I have been battling this code for a long time, and haven't been able to get it to go away. I really hope its not a leaky gas tank, because that would just suck. I'm going to inspect the canister tonight, and hope that it's that, because that's a relatively inexpensive repair and it's easy to do. Any other suggestions on where to look?

 

Thanks in advance, and speedy, on-topic replies are appreciated.

[vengeful]

Dean, Lewis, I know you guys have dealt with emissions crap before...any ideas?

[vengeful]

I just thought of something else to add:

 

P0158/P0159

 

I had not had these codes present before I moved to Phoenix. I'm used to using whatever is the cheapest gas around, and in NY, that's Delta Sonic, which uses Shell gas.

 

Here in Phoenix, the cheapest gas stations are Arco. I thought Arco would be good, being that they're subsidiaries of BP, the gas stations I use when I'm in VA. I guess I was wrong. My truck rattled like a son-of-a-gun using Arco Gas, but I dismissed it as simply a rattling heat shield - I was wrong. I recently filled up at a Shell station, and the rattling disappeared. My truck was pinging like nothing I've ever heard.

 

I wonder if that would have caused these O2 sensor codes. I'm going to leave the O2 sensor stuff be for a few days, and recheck the ECM after running more of this detergent Shell gas through my truck.

 

Comments?

[02silverpathy]

Hey Venge,

I have done tons of homework on these parts with all my other troubles.

 

That IACV, gets gummmed up all the time in Nissans, particularly with these intake manny's...something to do with the location of PCV and how they flow by each other. Unbolt from the back and try to clean it. I have yet to do mine, but the dude working on my truck says that is the same reason that my Idle flexes up and down quickly when it first starts.

 

Your knock sounds like the connector has had enough...it needs cleaned out of any debris, we all know that the knock goes dead at a young age in these rigs, however mine made quite a difference with cams. This part actually helps the truck advance its own timing. I would bet that you got some dirt in the connector making it arc funny.

 

That 1440...positive pressure...I would definately check that large plastic one way valve that is just behind the bumper...if those hoses are dried up it may allow the system to breath back wards...of course any of those pesky hoses under neath could be dry due to location and that fact that you actually drive your rig offroad!!

 

O2 sensors...well break open the wallet...I think that 88 had a method for cleaning them that my be useful.

 

good luck my man!

[lewisnc100]

Mine was easy, had vent control error with small leak, replaced both canister and valve and haven't had the error again. Didn't really have to investigate very far since I also had the vent control valve error.

 

Beyond doing a smoke test and checking the lines for the small leak, you might look at the gas cap. It's not just a question of whether its on tight, it also has an internal vacuum relief valve that could be leaking.

 

This is from the gas cap testing procedure: Check valve opening pressure and vacuum. Pressure: 15.3 - 20.0 kPa (0.156 - 0.204 kg/sq.cm, 2.22 - 2.90 psi) Vacuum: -6.0 to -3.3 kPa (-0.061 to -0.034 kg/sq.cm, -0.87 to -0.48 psi)

[vengeful]

Update:

 

I've replaced the fuel filter and I've done the electrical diagnosis on the O2 sensor and the IACV Valve. The O2 sensor is functioning properly...crap. The IACV Valve circuit is OK, meaning the IACV Valve itself is at fault, whether it's simply gummed up, or it's broken is left to be determined.

 

I did a scan on the DTCs and came up with the following list:

 

P0505

P0325

P0505 Pending

P0325 Pending

P0158

P0159

P0440

P1448

 

Now the EVAP Vent Control Valve is stuck open, and the EVAP System has Negative Pressure.

 

I have all new EVAP parts, Canister and the two valves that go by the Canister, as well as the O-Ring seals and what not. I'm waiting on the bolts and mounting hardware to arrive before I tackle it, because the bolts on there now are severely rusted and will probably just break when I try to take them out. I've been spraying them with loads of PB Blaster in hopes that I can get them out whole, but I'm skeptical.

 

The continued O2 sensor codes lead me to believe that the problem is either a fouled injector or an intake air leak. I'd almost prefer a leaky intake gasket to a fouled injector.

 

I've erased the codes, and we'll see what comes back in the next couple days.

[vengeful]

Ok, I was just going back through all of my old posts, and found this...Figured I ought to update everyone on the situation.

 

Over Christmas break, I brought my truck into the shop to have it checked out because it was going to fail emissions, and I needed to renew my registration. Anyhow....here goes.

 

After a week in the shop, it was determined that I had several problems.

 

The Bank 2, Sensor 2 O2 sensor was faulty - replaced.

 

The Throttle Position Sensor had a bad connection in it at 5% throttle, which was causing the IACV-AAC valve and the EVAP Vent Valve to flutter, causing my stalling problem. Replaced the TPS.

 

The truck had been in the body shop since my idle issues began and apparently the body shop had attempted to adjust the idle using the adjustment screws on the TB and totally FUBAR'd it. Replaced the Throttle Body.

 

The IACV-AAC Valve was experiencing intermittent shorts, so it too was replaced.

 

After replacing the EVAP Canister, lines, and valves twice each, the EVAP codes still existed in the system. After replacing the TPS, the EVAP codes went away.

 

So, if you're experiencing an EVAP code, the problem may be something not-so-obvious.

 

All of this, including the long hours of diagnostic labor, cost me about $2200.

 

However, the truck is running better than ever, and on the way back from VA to NY (non-winter blend gasoline), I recorded 18.4mpg on the highway!! Beating my previous mileage account of the same trip by nearly 4mpg!

[zonianbrat]

Glad to hear your truck is running good Vengeful but dam :o $2200. That is a kick in the pants!!

[zonianbrat]

Hey Vengeful, did you ever do that tranny swap???

[nissandoms47]

he hasnt yet.

[Casey.T]

All of this, including the long hours of diagnostic labor, cost me about $2200.

Dam.... You could have bought a nice little WD21 for that...

 

Seriously, glad it up and running the right way again...

[r0x]

Re:

 

P0505 "Idle Air Control System" IACV-AAC

 

OK, here's my story... My 1998 Pathfinder stalled on I-95 this past Thursday @ 187,200 miles. The repair shop's diagnosis was a complete ignition system failure. They replaced the distributor assembly + cables + all 6 plugs. (There was an obvious crack in the ignition coil and a couple of burn-throughs on the cables.) All was good until the "Service Engine Soon" light came on within blocks of the shop. I returned right away and they took an error code reading ("EGR"-related? I'm not sure...) that prompted them to clean the air intake on the fuel throttle body, which was indeed dirty. (The fuel throttle body assembly had been replaced within the past couple of years.) I drove around for a while on city streets and all seemed to be good again. I then got on I-95 and things were still good. About 30 minutes later the "Service Engine Soon" light came on again just after I had exited the highway, at which point I was on city streets in slower traffic. Other than the "Service Engine Soon" light being on there doesn't seem to be anything wrong with the truck.

 

Later that evening I decided to buy an OBD-II reader and it returned P0505. When I erased the code it comes back almost right away and the "Service Engine Soon" turned on again soon thereafter.

 

Questions:

 

- Is the P0505 error related in any way to the distributor failure and subsequent repair?

- Where is the IACV-AAC idle control valve located? I can't find the thing for the life of me... Is it really somewhere close to the firewall next to plug #6? (A photo would be very helpful if somebody happens to have one handy...)

- What is the usual repair? Replacement?

- The truck starts right away, runs fine, and idles at about 750 to 1000 RPM when stopped and in gear. Is there any urgency to getting this repaired? I just spent $640 on a brand new ignition system...

 

Thanks, r0x

[chappy]

I'm about to tackle an evap issue myself with the vacuum cut valve bypass valve. Is there any precaution that I should take. I know one of the lines to the cut valve is attached to the gas tank to process the vapor so should I cinch the vapor line from the tank?

[r0x]

UPDATE: I discovered that the idle control valve is inconveniently located behind and under the EGR valve and that it faces the firewall. It's just about the most inaccessible part of the engine. My local Nissan dealer says that repair is by replacement. They want ~$200 for a new valve and ~$550 for labor, which involves removing the exhaust manifold in order to be able to get to the freakin' thing.

 

The only good thing is that in my case the idle control valve is stuck in a somewhat open position. The practical effect is that I get high RPM's, about 1500, only when the engine is cold. Idle goes down to about 750 RPM when the engine is warmed up and in gear, which is normal. So in my case I can live with the bad valve and the SES light. Perhaps if there is another reason to remove the exhaust manifold I'll have the idle control valve replaced at the same time. The bottom line is that it's a bad design - there's no reason for the valve to be there when it could have been up front near the throttle body.

 

Re:

 

P0505 "Idle Air Control System" IACV-AAC

 

OK, here's my story... My 1998 Pathfinder stalled on I-95 this past Thursday @ 187,200 miles. The repair shop's diagnosis was a complete ignition system failure. They replaced the distributor assembly + cables + all 6 plugs. (There was an obvious crack in the ignition coil and a couple of burn-throughs on the cables.) All was good until the "Service Engine Soon" light came on within blocks of the shop. I returned right away and they took an error code reading ("EGR"-related? I'm not sure...) that prompted them to clean the air intake on the fuel throttle body, which was indeed dirty. (The fuel throttle body assembly had been replaced within the past couple of years.) I drove around for a while on city streets and all seemed to be good again. I then got on I-95 and things were still good. About 30 minutes later the "Service Engine Soon" light came on again just after I had exited the highway, at which point I was on city streets in slower traffic. Other than the "Service Engine Soon" light being on there doesn't seem to be anything wrong with the truck.

 

Later that evening I decided to buy an OBD-II reader and it returned P0505. When I erased the code it comes back almost right away and the "Service Engine Soon" turned on again soon thereafter.

 

Questions:

 

- Is the P0505 error related in any way to the distributor failure and subsequent repair?

- Where is the IACV-AAC idle control valve located? I can't find the thing for the life of me... Is it really somewhere close to the firewall next to plug #6? (A photo would be very helpful if somebody happens to have one handy...)

- What is the usual repair? Replacement?

- The truck starts right away, runs fine, and idles at about 750 to 1000 RPM when stopped and in gear. Is there any urgency to getting this repaired? I just spent $640 on a brand new ignition system...

 

Thanks, r0x

[Fukinitupagain]

F*ck emmissions laws! If it weren't for these frivulous laws I'd have a Nissan Skyline.

[r0x]

I found these "urban" IAVC-AAC cleaning instructions on another forum:

 

http://forums.nicoclub.com/zerothread?id=251133

 

Ghetto way to clean iavc is.

step 1. start car

step 2. while having a friend rev engine, partially remove the 2ND (bigger of the 2 hoses) right beside eachother on your intake(stock - going from engine to airbox)

step 3. if you have managed to keep car running while pulling it PARTIALLY OFF then continue if not restart

step 4. spray a **** load of throttle body cleaner in there and reatach hose while keeping engine running.

repeat as needed

 

I am toying with the idea of trying this because the idle control valve is virtually impossible to get to on a Pathfinder without taking half of the engine apart. Any comments appreciated.

[Fukinitupagain]

I think eventually I am just going to re-title my Pathy as a '95 so I don't have to worry about that crap here in NC

[13bravo]

this may help alil.

 

 

SERVICE PROCEDURE

IMPORTANT: Before disconnecting any hose, make sure you mark the hose so it can

be correctly re-installed later. If a hose is incorrectly re-installed, the MIL will come

on.

1. Disconnect the vacuum hose from the EVAP System Pressure Sensor (see Figure 3).

CAUTION: The vacuum hose must be disconnected from the Pressure Sensor to prevent it

from being damaged.

Figure 3

2. Disconnect the Purge hose from the EVAP canister port labeled “Purge” (see Figure 3).

3. Disconnect the hose from the EVAP Purge Volume Control Valve (or Purge Cut Valve, if

equipped). Refer to Figures 1, 2, and 4 to determine which hose to disconnect based

on the type of Purge Volume Control Valve on the vehicle (i.e., duty cycle or step motor

type).

IMPORTANT: Before disconnecting any hose, make sure you mark the hose so it can be

correctly re-installed later. If a hose is incorrectly re-installed, the MIL will come on.

B. Cover the EVAP System Pressure Sensor hose with your finger, then blow air

through the Purge hose/EVAP system piping to remove charcoal particles

C. Repeat steps A and B until ALL charcoal particles are removed.

If all charcoal particles cannot be removed from the EVAP system piping using this

method, remove the piping from the vehicle. Then blow air through the piping while

moving it in different positions until all particles are removed. If this does not work,

replace the underbody piping.

5. Inspect the following components (refer to Figures 1 and 2) for charcoal particles. If

charcoal particles are found, carefully remove the particles from the component(s) and

the hoses that connect to them.

• Purge Volume Control Valve

• Purge Cut Valve (if equipped)

• EVAP System Pressure Sensor

• Vent Control Valve

• Vacuum Cut Valve Bypass Valve

• Vacuum Cut Valve

• Water Separator (and associated hoses)

IMPORTANT REMINDER: Before disconnecting any hose, make sure you mark

the hose so it can be correctly re-installed later. If a hose is incorrectly reinstalled,

the MIL will come on.

NOTE: It is very important to remove all charcoal particles as it only takes a small

amount of particles to store DTCs and cause the MIL to turn on. If you cannot remove

all charcoal particles, replace the contaminated (un-cleanable) component(s).

6. Re-assemble the EVAP system.

7. Erase all stored DTCs.

8. Road test the vehicle until the EVAP SRT shows “Complete”, then re-check for any

stored DTCs.

CLAIMS INFORMATION

For replacement of the EVAP canister and EVAP system charcoal debris

cleaning/removal, submit a Primary Failed Part (PP) line claim using the following

claims coding. To claim for diagnostic time(s) associated with the DTC code(s)

and/or the replacement of those components that have been rendered non-functional

due to charcoal contamination, reference the current Nissan "Warranty Flat Rate

Manual" and use the indicated Op Codes and FRTs