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Discussion Starter #1
2002 G20, Auto.

Hi, I've run the gamut trying to repair surging, bucking at low speeds and now I'm on to the "replace the IACV" theory. Yes, I had the computer repaired, thanks, and everything else I've discovered over the past three years. I've just lived with it until I found the Hitachi OEM IACV cheap on eBay from an Infiniti dealer.

My question is how to change it. I can't seem to access the screws well enough. Do I remove the manifold that it is attached to? If so, should I have a gasket or gaskets on hand? Which gaskets? I have to try to prepare so I don't have too much down time.

Thanks guys.
 

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Which code(s) appears when you pulls codes from the ECU?
I ask because 7 or 8 years ago when my engine was bucking and chugging fuel, it turned out to be the knock sensor that was causing the problem. I thought that sensor was fine because it didn't appear to be cracked, but that was because I didn't remove it, inspect or test it (resistance). It was impossible for me to remove it due to the lack of space to maneuver a wrench where it is mounted on the engine block, under the intake.
I should have removed it and tested it first, primarily because that knock sensor code was the code that the ECU was producing. Instead, I went about investigating and suspecting other things, testing a bunch of other stuff, removed and cleaned the IACV, replaced the Auxiliary Air Valve, fuel regulator etc. Lesson learned.
Recently, my engine started chugging fuel and running rougher. Turned out to be due to several things. I had a kinked and shorted knock sensor sub-harness, a shorted ground wire from the MAF sensor, and a torn rubber vacuum hose running from the EVAP Carbon Canister to the hard line running back to the gas tank. I replaced the KS sub-harness, replaced the torn hose and re-grounded the MAF sensor with a new ground wire. Now, no more problem codes on the ECU, but this time my starting point was where the ECU said the code problem was.
 

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If your IACV is on the end of the Intake plenum, it should be accessible without too much difficulty. Regardless, if you remove the plenum in order to access your IACV, you will need to source an IACV Seal and intake manifold gasket. If you separate the plenum from the throttle chamber, your need to replace the TBC gasket You can identify the parts better using this Nissan resource:
ENGINE MECHANICAL and FUEL AND ENGINE CONTROL:
2002 Nissan Sentra > Fuel & Engine Control > Throttle Chamber
IACV
IACV Seal O-ring
and Manifold gasket,
and Throttle Body Gasket
Just confirm that the 2002 Sentra and 2002 G20 have the same engine set up before buying anything.
For my wiring sub-harness, I contacted Wiring Specialties out of Brookfield, CT.
 

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Discussion Starter #6
If your IACV is on the end of the Intake plenum, it should be accessible without too much difficulty. Regardless, if you remove the plenum in order to access your IACV, you will need to source an IACV Seal and intake manifold gasket. If you separate the plenum from the throttle chamber, your need to replace the TBC gasket You can identify the parts better using this Nissan resource:
ENGINE MECHANICAL and FUEL AND ENGINE CONTROL:
2002 Nissan Sentra > Fuel & Engine Control > Throttle Chamber
IACV
IACV Seal O-ring
and Manifold gasket,
and Throttle Body Gasket
Just confirm that the 2002 Sentra and 2002 G20 have the same engine set up before buying anything.
For my wiring sub-harness, I contacted Wiring Specialties out of Brookfield, CT.
Thank you. That's really helpful. I'm getting P0505 and P0420.
 

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Check out this thread. The first post has a list of Engine Trouble Codes.

There are a few threads on this forum that talk about the code P0420, Catalyic Converter related. TroubleCodesP0420 info
P0505 is IACV related.
I took mine off and cleaned it out with a metal pick and then carb cleaner. It was very sooty. Not that it is indicative of the problems your codes point to, but when you pull your intake plenum, look inside it. If it is coated with sludge inside, there is oil-laden blow-by air entering the intake via the crankcase ventilation hose (which connects to the main air intake boot just before the throttle body. A very knowledgeable fellow told me that was due to running the throttle (driving or revving) while the engine is cold or damaged piston rings that allow oil mist to escape more than normal into the crank case and be pulled out and into the intake recirculation, where it would eventually end up accumulating inside the intake plenum, IACV and intake manifold. If the plenum and intake manifold are gunky inside, you might also change the pcv valve. It might be gunked up, too.

What do your spark plugs look like?
 

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Discussion Starter #8
Check out this thread. The first post has a list of Engine Trouble Codes.

There are a few threads on this forum that talk about the code P0420, Catalyic Converter related. TroubleCodesP0420 info
P0505 is IACV related.
I took mine off and cleaned it out with a metal pick and then carb cleaner. It was very sooty. Not that it is indicative of the problems your codes point to, but when you pull your intake plenum, look inside it. If it is coated with sludge inside, there is oil-laden blow-by air entering the intake via the crankcase ventilation hose (which connects to the main air intake boot just before the throttle body. A very knowledgeable fellow told me that was due to running the throttle (driving or revving) while the engine is cold or damaged piston rings that allow oil mist to escape more than normal into the crank case and be pulled out and into the intake recirculation, where it would eventually end up accumulating inside the intake plenum, IACV and intake manifold. If the plenum and intake manifold are gunky inside, you might also change the pcv valve. It might be gunked up, too.

What do your spark plugs look like?
Plugs are clean and dry. The information you provided is over the top helpful. Thank you. Have many children and teach them your ways.
 

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Ahhh, yes. There must be a thread for that here. hahaha The clean and dry plugs is a good sign, but the ceramic tip should be a little toasty instead of gleaming white. (That is what you want.) I was asking in order to see if the oil was getting past the a piston ring into the combustion chamber and fouling out that plug, which would then be unable to ignite the fuel like it needed to, the excess fuel and wet oil in that cylinder be pushed out with the exhaust where it would probably mess up on oxygen sensor and/ or the catalytic converter. I want to say that a catalytic converter code could be an oxygen sensor and not necessarily the catalytic converter. You'll have to research that one, but it somehow rings a bell with me.
 

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Discussion Starter #10
Ahhh, yes. There must be a thread for that here. hahaha The clean and dry plugs is a good sign, but the ceramic tip should be a little toasty instead of gleaming white. (That is what you want.) I was asking in order to see if the oil was getting past the a piston ring into the combustion chamber and fouling out that plug, which would then be unable to ignite the fuel like it needed to, the excess fuel and wet oil in that cylinder be pushed out with the exhaust where it would probably mess up on oxygen sensor and/ or the catalytic converter. I want to say that a catalytic converter code could be an oxygen sensor and not necessarily the catalytic converter. You'll have to research that one, but it somehow rings a bell with me.
Yessir. I r&r'd the O2 sensors but no joy. I'm not sure I want to replace the catalytic converter. The car may be on it's way to being done. I'm original owner with around 250k miles.
 

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Discussion Starter #11 (Edited)
Ahhh, yes. There must be a thread for that here. hahaha The clean and dry plugs is a good sign, but the ceramic tip should be a little toasty instead of gleaming white. (That is what you want.) I was asking in order to see if the oil was getting past the a piston ring into the combustion chamber and fouling out that plug, which would then be unable to ignite the fuel like it needed to, the excess fuel and wet oil in that cylinder be pushed out with the exhaust where it would probably mess up on oxygen sensor and/ or the catalytic converter. I want to say that a catalytic converter code could be an oxygen sensor and not necessarily the catalytic converter. You'll have to research that one, but it somehow rings a bell with me.
Yessir. I r&r'd the O2 sensors but no joy. I'm not sure I want to replace the catalytic converter. The car may be on it's way to being done. I'm original owner with around 250k miles.
 

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Don't take my suggestion as fact. Let a mechanic tell you what's going on with it. If the spark plugs are clean and dry, not oily, crusty-white or wet, that motor is still in good shape. If your cylinder compression is still around 160-180 psi, it is stll aliiiiiiiiive!! I wouldn't give up on your car over the catalytic converter, assuming that is in fact what is causing the problem codes.
Where are you located?
 

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so here's what i've found hope this help


Step 1: Disconnect the battery. Disconnect the negative battery cable from the battery and set it aside.

Step 2: Locate the valve. The location of the idle control valve will depend on the make and model of your vehicle. Your vehicle’s owner’s manual will have information on the exact location. The valve will nearly always be located on the intake manifold.

Step 3: Disconnect the wiring harness. Locate the wiring harness connected to the valve and release the electrical terminal from the valve.

There will be a clip or a tab to disconnect, and it might be easier to gently remove it with a pair of pliers.

Step 4: Remove the old idle control valve. Remove each of the valve’s retaining bolts.

With the bolts and wires now removed, the valve should just pull out of place.

Step 5: Clean the seat. With the seat for the valve exposed, use the throttle body cleaner to clean the area you will attach the new valve to. This assures a clean seal between the valve and its seat.

Step 6: Install the new valve. First, compare the old valve you are replacing with the new valve. Verify that the wiring terminals, retaining bolt pattern, and seat placement are all the same.

Then put the new valve in place and install the retaining bolts, hand tightening them to the seat. Use your socket and ratchet to snug them down gradually one by one.

Warning: Do not overtighten the bolts because it may cause a leak or improper function with the system.
Step 7: Reinstall the wiring harness. Reattach the wiring harness to the valve. Ensure the terminal is making a proper connection and the clip is fully engaged to secure this connection.

Step 8: Reconnect the battery. Reattach the negative battery cable to the battery. Tighten down the bolt so that any engine vibration won’t rattle it loose. This will restore power to the vehicle.

Step 9: Test the idle speed. Start the engine and observe idle speed. Depending on your particular vehicle and ambient air temperature, your idle speed should hold steady between 550 RPMs (at the very lowest when it’s hot outside) and 1,000 RPMs (at the highest and at lower temperatures).

Having a properly working idle control valve will make a huge difference in the driveability of your vehicle. Even beginners should be able to replace this valve. However, you can always contact one of the certified technicians from governor automotive to replace your idle control valve for you.
 

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Discussion Starter #14 (Edited)
Don't take my suggestion as fact. Let a mechanic tell you what's going on with it. If the spark plugs are clean and dry, not oily, crusty-white or wet, that motor is still in good shape. If your cylinder compression is still around 160-180 psi, it is stll aliiiiiiiiive!! I wouldn't give up on your car over the catalytic converter, assuming that is in fact what is causing the problem codes.
Where are you located?
It' s not the catalytic converter that bothers me. It's the lack of driveability with tbe bucking and jerking at low rpms. The cat problem just adds to the growing expense of a vehicle needing unresolvable repairs, it seems. I mean, if I give this car to my teenager, I don't want to worry about it catching on fire. I might just buy him a newer Nissan sentra to get to get him safely fro A to B, for example. I'm in Santa Rosa, CA.
 

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That bucking and jerking at low rpms sounds like a disconnected MAF sensor or something bad in the knock sensor circuit, the sensor or the sub-harness. But if you are not getting either of those codes, I guess they are not the source of the problem. I didn't understand what you meant when you said you had "r&r'd the oxygen sensors".
If it were my car, I would be thinking "Hmmm, A new catalytic converter (if that is what is causing the symptoms) costs way cheaper than a newer Sentra."
I am not familiar with the 2002 G20. Does it have a distributor? If so, make sure your timing is where it should be and hasn't been retarded by a loose distributor bolt.
 

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Discussion Starter #16 (Edited)
Don't take my suggestion as fact. Let a mechanic tell you what's going on with it. If the spark plugs are clean and dry, not oily, crusty-white or wet, that motor is still in good shape. If your cylinder compression is still around 160-180 psi, it is stll aliiiiiiiiive!! I wouldn't give up on your car over the catalytic converter, assuming that is in fact what is causing the problem codes.
Where are you located?
Yes, removed and replaced the MAF sensor and every other easily replaceable part related to the symptoms. The catalytic conver is not related to the poor performance as far as my research has indicated. it just might cause the car to catch fire. If I can't resolve the driveability and there is a risk of fire, I won't keep the car. If I can resolve the driveability, I will then consider replacing the cat based on the code and temperature readings because then the car would be driven on a regular basis. Follow my reasoning? The distributor was recently replaced so I'll revisit that too. Thanks.
 

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Discussion Starter #17
so here's what i've found hope this help


Step 1: Disconnect the battery. Disconnect the negative battery cable from the battery and set it aside.

Step 2: Locate the valve. The location of the idle control valve will depend on the make and model of your vehicle. Your vehicle’s owner’s manual will have information on the exact location. The valve will nearly always be located on the intake manifold.

Step 3: Disconnect the wiring harness. Locate the wiring harness connected to the valve and release the electrical terminal from the valve.

There will be a clip or a tab to disconnect, and it might be easier to gently remove it with a pair of pliers.

Step 4: Remove the old idle control valve. Remove each of the valve’s retaining bolts.

With the bolts and wires now removed, the valve should just pull out of place.

Step 5: Clean the seat. With the seat for the valve exposed, use the throttle body cleaner to clean the area you will attach the new valve to. This assures a clean seal between the valve and its seat.

Step 6: Install the new valve. First, compare the old valve you are replacing with the new valve. Verify that the wiring terminals, retaining bolt pattern, and seat placement are all the same.

Then put the new valve in place and install the retaining bolts, hand tightening them to the seat. Use your socket and ratchet to snug them down gradually one by one.

Warning: Do not overtighten the bolts because it may cause a leak or improper function with the system.
Step 7: Reinstall the wiring harness. Reattach the wiring harness to the valve. Ensure the terminal is making a proper connection and the clip is fully engaged to secure this connection.

Step 8: Reconnect the battery. Reattach the negative battery cable to the battery. Tighten down the bolt so that any engine vibration won’t rattle it loose. This will restore power to the vehicle.

Step 9: Test the idle speed. Start the engine and observe idle speed. Depending on your particular vehicle and ambient air temperature, your idle speed should hold steady between 550 RPMs (at the very lowest when it’s hot outside) and 1,000 RPMs (at the highest and at lower temperatures).

Having a properly working idle control valve will make a huge difference in the driveability of your vehicle. Even beginners should be able to replace this valve. However, you can always contact one of the certified technicians from governor automotive to replace your idle control valve for you.
Thank you. I am needing advice accessing the IACV. Must I remove the intake plenum? I can't access all of the screws that fasten the IACV to the throttle body.
 
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