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Mechanic recommends replacing intake manifold…fault code popped up while repairing something else: FOUND CODE 0521 THE CHARGE MOVEMENT FLAP (CYLINDER BANK 1) HAS A MALFUNCTION.
Dealer advised of defective intake manifold code when repairing airbag eight months ago. I demurred for financial reasons.
It’s a 2010 C300 Sport with 132,500 miles. I’m considering deferring unless check engine light comes on. No symptoms of bad intake manifold as far as I can tell. Any thoughts on pros and cons of would be greatly appreciated.
You can just about see the various small diameter rubber vacuum hoses (lot of them !) for the actuator diaphragms that move the intake manifold flaps. Usually when the plastic arms are broken or off completely, it will throw a permanent 05XX code and your acceleration from idle and gas mileage will suffer. Intermittent code can be from failing diaphragm or leaky vacuum hose(s), less often the internal flaps get hung up from shaft wear on the plastic. . Take off the 2 engine top covers and check out these components. Beside brittle hoses which at your mileage and Cali heat certainly may be leaking at metal connects, check the metal actuator rods aren't corroded. coated with that white oxide layer and sticking also.
If you are in the mood, change out all those rubber lines even if they look fairly OK and clean up any corrosion.
I'm not handy so on one hand I could just keep driving until the check engine light comes on, on the other I'm worried that doing nothing may compromise the engine overall.
Gotcha...the worse scenario, rather rare, is that the plastic pieces inside the IM which make up this "make intake runners longer at low loads, shorter at high engine loads" flap system break up and are ingested thru the intake valves..should have a CEL and poor engine response, stumbles before that strikes.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Gotta ask what side of the air filter these flaps are. Then consider, as mentioned, parts getting sucked into one or more cylinders. Not a chance I would want to take.
Gotta ask what side of the air filter these flaps are. Then consider, as mentioned, parts getting sucked into one or more cylinders. Not a chance I would want to take.
Talking 272 V6 C300 (08- 11) here..Post Air Filter(s).....the rearward upper engine cover with 2 air intake snouts contain the 2 air filters (look on underside where small Torx screws hold cover plates that access filters) . Filtered air from the 2 sides merge to exit rubber ringed 3" hole into IM where all the flap action occurs.
If I were getting a code P0521 I would remove the air filter box and inspect the front of the intake manifold looking for a broken lever. I would get it repaired as soon as possible.
Take the air filter box off and snap some photos and post them.
Figured better safe than sorry so had the intake manifold replaced yesterday. Picked the car up late afternoon and this morning when I started the car the CHECK ENGINE LIGHT came on. I connected my code reader and it said “P0301 Cylinder 1 Misfire Detected.” WTF?
Would check cylinder 1's coil/spark plug boot and fuel injector connectors first for poor connections. After clearing the code it may not reoccur.... Would check the crank/cam sensors connections too while at it but they would throw other specific to them codes if the problem.
I erased the code, started car, no check engine light. Drove for a bit and the check engine light came back on. Also noticed the engine feels a little bit bouncy while idling, like it’s going to stall even though it doesn’t. Since this came up exactly when I got the new intake manifold I assume there’s a correlation…?
Yep..that would be my guess. The shop who did the work needs to check her out. Pinched IM gasket sucking air for example causing lean AGE in a cylinder or 2.
If it were me I would remove and inspect cyl 1 spark plug. I would probably switch the coil with another cylinder to see if the misfire moves, indicating a bad coil. Obviously replace the spark plug while I'm at it.
I cant remember, do you have a Mercedes specific obd scanner or a basic one? Im surprised that is the only code that is showing.
I have a cheap crap scanner. I’m surprised it showed any code at all. I bought it because I’m a sucker and thought it would help when I replaced my rain light sensor but it didn’t work for that so I ended up having to bring it to the shop to have it calibrated properly.
I’m actually glad it’s not showing more codes because that would give me an aneurysm since I have to wait until Monday morning to bring it back in.
I had my 120K mile service and there’s now 133K on the car. I am assuming they replace the plugs but not the coils when they do that service…? I’m hoping it’s something as simple as a little boo-boo on the install like gamma300C suggested or the spark plug/coil.
Last edited by Aging C300; 01-27-2024 at 02:55 PM.
I have a cheap crap scanner. I’m surprised it showed any code at all. I bought it because I’m a sucker and thought it would help when I replaced my rain light sensor but it didn’t work for that so I ended up having to bring it to the shop to have it calibrated properly.
I’m actually glad it’s not showing more codes because that would give me an aneurysm since I have to wait until Monday morning to bring it back in.
I had my 120K mile service and there’s now 133K on the car. I am assuming they replace the plugs but not the coils when they do that service…? I’m hoping it’s something as simple as a little boo-boo on the install like gamma300C suggested or the spark plug/coil.
Fingers crossed is just a boo-boo as you said.
Intake manifold replacement is time-consuming, and requires care when assembling back:
1 - Careful not to introduce anything in the fuel rail if by any chance injector, or the rail were disconnected upstream. Minor debris will end up at the entrance of an injector and it will trigger a misfire on the cylinder the debirs stopped at
2 - Careful to set the gasket correctly; otherwise, a leak will trigger a misfire
3 - Careful with any electrical connection, for example, poor coil connection due to connector internal wear -> drag test they call it.
4 - Careful not to crack already brittle parts (like coils) and trigger arching, etc.
The shop said a leaky vacuum hose was the culprit in this case. Seems to be running great now. Actually, it seems a bit peppier, before the repair there used to be a (very) slight delay when I accelerated quickly, while changing lanes for example, and that is now gone -- but of course this could be a figment of my imagination as I try to justify this expensive repair to myself.
Thanks to all for all the advice, it has been very helpful and educational..
The shop said a leaky vacuum hose was the culprit in this case. Seems to be running great now. Actually, it seems a bit peppier, before the repair there used to be a (very) slight delay when I accelerated quickly, while changing lanes for example, and that is now gone -- but of course this could be a figment of my imagination as I try to justify this expensive repair to myself.
Thanks to all for all the advice, it has been very helpful and educational..
Great to hear. Keep up with the maintenance, and you will have a car for a long time.
I have the same exact car (2010 c300 sport) and I too am looking at replacing my intake manifold or just upgrading the flap in the front with the aluminum part made my URO. Is it advisable to clean the existing manifold, or would it be better to just get a new/remanufactured one. And if there are any remanufactured units out there with the upgraded aluminum flaps.
Since I didn't have the knowledge to make my own diagnosis or repairs, I took the technician's recommendation to replace the part with an OEM part that was about $200 less than the same part at the dealership. I guess I could've asked the shop to take everything apart to see if they could just fix the flap malfunction noted on the fault code, but at 133k I got nervous something else would break.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
It's not so much mileage as it is age. You were probably right to replace the whole assembly since you cannot do this yourself. You don't want to pay labor more than once.
01-23-2024, 11:46 PM
