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Discussion Starter #1
I have a 2005 300c that has developed a surge when it is at a constant speed, (most notably around 35). I had a code “P3497” pop up a few weeks ago, I changed the oil and it went out. About a month ago I had the transmission flushed at the local dealer so the fluids are fresh. The car is all stock and I pull a trailer with this car but the load is under a 1,000 pounds. I am perplexed with this issue, if anyone has any ideas please let me know. Thank you.
 

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What weight oil did you use? That code is related to MDS (Multiple Displacement System) operation:

Possible causes
- Low oil pressure
- Restricted oil passage
- Engine mechanical condition
- Multiple Displacement System (MDS) Solenoid fault

Although in some cases changing the engine oil may fix the problem, usually the Multi Displacement System Solenoid needs to be replaced.

The Engine Control Module (ECM) has detected a lean condition on bank 2 while in the 4 cylinder mode which why it set a code.
 

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Discussion Starter #3
I know about the oil that is why I changed it. The code went out after the change but the symptoms started about 600 miles later. The car stalled on me twice yesterday and has yet to pop another code. After restarting it ran fine. I’m starting to get a little worried that it is going to strand me on the side of the road and that is the last thing I need.
 

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In part, here is what the service manual says:

P3497-MDS RATIONALITY BANK 2
Theory of Operation
When all criteria has been met, power is supplied to each MDS Solenoid when the engine is making a transition
from 8 cylinder mode to 4 cylinder mode. By actuating the solenoid, oil pressure is raised to the pair of lifters that
coincide with each particular solenoid. The oil pressure pushes in the locking pins that allows the lifter to collapse,
decoupling the valves and camshaft.
When Monitored:
Transition from 8 to 4 cylinder mode.
Set Condition:
O2 sensor readings on Bank 2 side indicate a lean condition while in 4 cylinder mode.
Possible Causes
INSUFFICIENT OIL PRESSURE ACTING ON THE LIFTER LOCKING PINS
OIL PASSAGES RESTRICTED
LIFTER
MDS SOLENOID

There is much more in the service manual, most of which requires the Starscan tool and engine disassembly.

How many miles are on the engine?
Have the oil and filter been changed at recommended intervals with recommended type and grade of oil?
Has the engine operating temperature been pushed to high extremes?
Do you frequently drive short distances during which the engine does not reach proper operating temperature?
Are you using the recommended octane fuel?

If I were having this problem I'd start with an engine flush followed immediately with an oil and filter change to more or less assure that the oil passages were not restricted, and go from there.
 

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It sounds to me like he was having the code before he did the oil change. Since then his code is clear and no more issues that way... the surge and stall at 35mph seems to be a new issue. No more codes with this new issue, correct? Do you have any mods at all? Tune etc?

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Discussion Starter #6
Silver06hemic: You hit the nail on the head, (no wait that’s an old Buick lol) Yes the code cleared after the oil change and this is a new issue. The car is stock; no mods or tunes. It is also a sporadic issue I drove the car all day today with no problems yet yesterday I didn’t think I would get to my destination. No new codes have popped, yet.
Thanks.
 

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A quick and easy change that can sometimes assist with rough idle and surging is the cam position sensor... also the crank sensor can cause some issues as well. The parts are inexpensive and anyone can change them who could change a tire or do an oil change. My cam sensor was puking and she ran rough and stalled a lot... no codes... 5 min change and fixed. Now if its not that then it was a cheap start... from there crank sensor... from there it gets more technical and more expensive. Not a for sure fix but its a good start and cheaper than dumping it at the dealer to pour money into or to hear 'could not replicate'...

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Discussion Starter #9
Still got the hiccup

Ok folks I changed out the crank sensor and it was no help. However I did notice that this problem seems to happen just after I get gas, (and no I do not over fill the tank). The problem does seem to lessen after a few miles. Before I go out and buy a cam sensor are there any other suggestions related to fuel? BTW on the 5.7 the starter must be removed to replace the cam sensor. Not recommended when the engine is hot. Still an easy job though.
 

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Discussion Starter #11
Cleaned the throttle body first. It was caked but a clean unit didn’t change the problem. What would cause a fuel fill up to make the problem worse?
 

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There has been a lot of excellent suggestions thrown at you so I will add a few more

*Sticking PCV valve
*EGR valve going bad
*Throttle Positioner needs recalibrated

If at anytime you have overfilled the gas tank then there is a good possibility that you have damaged the Evap System. Next time you need gas, only fill to 3/4 full and see if that makes a diff.
Also see if the "surge" goes away (temp) if you downshift or drive in 4th gear at the "surge" speed. Keeping the tranny from going to 5th gear will keep the MDS from activating.

Keep us posted on your progress.
 

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Ok folks I changed out the crank sensor and it was no help. However I did notice that this problem seems to happen just after I get gas, (and no I do not over fill the tank). The problem does seem to lessen after a few miles. Before I go out and buy a cam sensor are there any other suggestions related to fuel? BTW on the 5.7 the starter must be removed to replace the cam sensor. Not recommended when the engine is hot. Still an easy job though.
Actually the crank sensor is behind the starter... the cam sensor is just below the throttle body on the passenger side of the car held in by one bolt ;) Both are pretty simple... just to change the crank sensor you have to pull the starters couple of bolts and slide it out of the way... it takes five mins more than the cam sensor... but it is in a more awkward spot.

You could try a new gas cap... no clue why it can cause an issue but I had a VW that threw codes every time I started it after a refill... dealer had no clue... changed all kinds of stuff. One day I found my auto popper for my gas door had been forced and my gas cap missing... I cursed and went and bought a new one. Took two mins to realize why it was stolen... stupid pricey and at that time only at the dealer, long story short... never had another code issue again. Now that was a code, car ran fine, just seemed possibly relevent! Lol.

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Discussion Starter #14
The crank and cam sensors are switched out and the throttle body is clean as a whistle this is not my problem. The problem seems to be worse after getting gas so I’m starting to think Evap, but no codes so I’m very confused.
 

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Hmmmm.... ok.... back to the drawing board.... :( Have you done a suction test on the gas cap? Napa used to do them... I will ask my local one which is five mins away tomorrow. You could try a PCV and see if that helps, but I feel it wouldn't make that big of a difference if it was not completely functional. EGR can be shut off completely and when my first valve went bad it threw a code but responded perfectly normal... hmmm. Let me think on this one... I am amazed it wasn't cam or crank sensors... :confused: :banghead:

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