Model: XG350L, Year: 2004, Mileage: 70,000

I've recently become aware of a slight rough idle situation. I had the dealership replace the plugs and plug wires AND clean the fuel system. The rough idle persists. The service manager suggested I clean or replace the Air Flow Sensor. This unit is expensive and therefore I asked that it be cleaned to which he replied, "We do not clean them." I bought a can of CRC Mass Air Flow Sensor Cleaner BUT I cannot remove the 2 screws that secure the sensor. It appears to be a Torx Security bit however the center pin diameter in the screw socket appears to be too large for a T-20 Torx. The next standard size Torx is a T-25 and it is too large for the screw.

If I can't remedy the rough idle by cleaning the sensor then I will have to replace the unit. In either case I will need to remove the 2 screws holding the sensor in place. Why does Hyundai use this non-standard screw? It makes it impossible to service or replace the Air Flow Sensor.

Thank you for your assistance.

dikjenkins

 

Can you use a socket to remove the screws? I know here in the US, many times it's a bolt head with a torx or phillips pattern in the top.

I don't know what vehicle the pic below is from but it's similar to your setup and it clearly shows the clamps having both a phillips head and a bolt head.

 

Are you trying to remove the MASS air flow sensor body from the intake or are you trying to remove the sensor itself from the body? I now see NovaResource has responded with a similar thought. You only need to loosen the hose-style clamps that secure the sensor body between the air filter box and the throttle body intake tube. Swing the body up to look down the passage, you should see the business end of the sensor protruding inside.

I'm also thinking somethings not right with the dealer's recommendation. If the MASS air flow sensor is malfunctioning because of dirt or some other condition to the point it affects the idle, the check engine light should come on and generate a code. If the dealer is "guessing" that this is the problem without such indicators, I'll be surprized if cleaning the sensor solves the problem.

 

The image posted does not resemble my situation. In retrospect what I should have posted as my problem was that I wanted to replace my air flow sensor and could not locate the proper tool to remove it. That being said the air flow sensor is screwed to a tube approx. 4 inches in diameter that connects the air filter outlet to the engine.

I've been aware of a slight roughness in my engine idle. I've owed the car since new and I'm aware of the slight roughness. There is a requirement to change spark plugs around 60,000 miles and so I asked that the plugs be replaced and because of the idle I suggested they also replace the plug wires. After all the dismantling that's required to replace the plugs I'd hate to repeat it for plug wires. Hyundai service reported that the roughness still existed after replacing these components and suggested they clean the system. My impression was that it was a solvent of some sort that was allowed to pass through the system cleaning it. They did and the roughness persisted.

Don't quote me now on the price but service told me the PART price of the air flow sensor was around $300. Somewhere around I'm saying. Service suggested I try cleaning the sensor with CRC Mass Air Flow sensor cleaner. I want to remove the sensor by removing the 2 screws that secure it to the 4 inch diameter air inlet tube and clean it. According to the instructions on the can of cleaning solvent (CRC product mentioned earlier) removing those screws requires "a T-20 Torx Security bit". That bit looks like any other Torx head screw EXCEPT it has a pin in the center of the Torx screw head. When I attempt to insert the T-20 sercurity bit into the Torx screw I find that the center pin protruding up in the center of the screw head is a bit too large for the hole present in the Torx security bit. The next larger Torx bit is a T-25. That bit is too big in its outer shape to seat inside the screw. Therefore I must comclude that Hyundai is using a non-standard Torx type screw for this air flow sensor. If I can't clean it then I must replace it. I can buy a replacement sensor from NAPA for about $170.

Foot note: I've been to 6 parts and tool houses and we have gone to the car and tried their tool in the screws and they don't work.

 

The sensor is not meant to be removed from the "tube". One of two situations exist: 1) Try unplugging the harness from the sensor and then undo the clamps that hold the "tube" the sensor is mounted to (the "tube" is the sensor body). Apply a twisting motion to slip the tube away from the filter box and the remaining intake tube leading to the throttle body. 2) Again, unplug the harness. On some cars (my 08 Sonata is one), the intake side of the sensor body is directly connected to the lid of the filter box. In this case, undo the clamp on the back and remove the sensor body/filter box lid as one unit. You should be able to clean the sensor without seperating the two.

The CRC product is not specific to any particular make or model of car. Any instructions regarding removal of the MAF sensor are general at best.

 

I've become curious about the instructions on the CRC can regarding sensor removal. I found the label at the CRC web site (http://www.crcindustries.com/faxdocs/label/lb05110.pdf). As you know, step 4 says "Remove the MAF housing (Typically a screwdriver will work, you may need a T-20 Torx Security bit)". Quite simply, the MAF housing is the "tube" you refer to.

Also, I finally located a graphic of a XG350 MAF sensor. Unplug the sensor housing at the large black arrow below and loosen the two large hose clamps at the two smaller arrows above.


[IMG]local://upfiles/4972/25619C0EED9A4E63BBCB6F44A147D9A5.jpg[/IMG]

 

The MAF includes the tube. You remove the tube, you do not remove the wires from the tube to clean it. Just remove the tube and spray it with the MAF cleaner, allow it to dry and reinstall.

 

was the timing belt done on the car? if so the timing might be off. personally i don't think cleaning the maf sensor will cure your problem.

 

Thanks all for your help and suggestions. Let me try to answer your questions and better explain my actions:

Yes the timing belt was changed at the prescribed mileage by Hyundai.

The service invoice states that a BG Induction KT was used to clean the system. Comments on the work order were:

"Customer states it idles rougher than it used to. Spark Plugs? Completed manufacturer plugs/wires interval to try and fix issue and perform an induction service. Car still has a slight rough idle possibly due to mass air flow issue caused by oils from K&N air filter." (end of quote)

I replaced the K&N permanent air filter with a throw away filter. I hadn't cleaned the K&N unit as required due to my ignorance. What I had done was removed it, rinsed it with water, allowed it to dry and reinstall. I had forgotten that I needed to use their nasty cleaner. I've used enough acetone to know to avoid it. I suspect his statement about the K&N unit was made to protect him (Hyundai) and point out I was not using genuine parts. Not really the issue.

I've had the "tube" removed from the car before to clean the throttle body so that will not be a difficult task. I was under the impression that the air flow sensor (AFS) was the element attached to the "tube" and held in place with 2 screws and that alone (AFS element) could be removed for cleaning. If you say that when the "tube" is removed and the AFS wires disconnected I will be able to look down the "tube" and spray clean the elements of the AFS throughly than that is what I will do. Does it seem to you that I am duplicating cleaning that was already performed by the Hyundai service department? "a BG Induction KT was used to clean the system."

Again.. thanks all for your expert help, I appreciate it.

 

Yes. Unplugging the sensor (so long as the ignition is off) will not harm it, just make sure it is plugged into the harness before you start the car. That will generate an error code and turn the CEL on. If you have room to tip the sensor body or tube up without disconnecting it from the harness, that's fine too. Follow the remaining instructions on the CRC cleaner can.

No. From what I could find on the Internet, the "BG Induction KT" (aka, BG Fuel Induction Cleaning Kit) is a combination of fuel additives and a spray aerosol. The aerosol contains "cleaners and lubricants" designed for the throttle body and air idle control valve. I don't think lubricants would be good for the heated film portion of the MAF (AFS) sensor, so I doubt the kit was used to clean it.