Having issues with engine running bad, mostly at idle or just starting to accelerate. Coughs and shutters sometimes. Replaced mass air flow sensor but still doing it at random. Have put 500 miles on car running it hard in arkansas but still not fixed. What else can be the issue? EGR valve? Help appreciated.

 

Forgot to mention the codes that are showing up , lean band one and two

 

It is actually Lean Bank 1 and Bank 2, not band.
Put the codes in the Google Search used on this forum and the answers appear as if by magic.

 

Diagnostic Trouble Code (DTC) List

P0171 System too Lean (Bank 1) ) faulty air mass flow sensor
P0174 System too Lean (Bank 2) )

 

Problem Solved
Figured I'd let others know what the problem was. Engine running lean and throwing the P0171 & P0174 codes due to small air leak. Only at idle would this symptoms appear. Ran great other wise. Searched and searched for leak using starter fluid on vacuum lines - found nothing. MAF sensor replacement didn't affect it. This rough engine at idle started soon after the oil change. Never put the two together.

On the oil cap is two triangles that one is to line up, I assume to indicate the cap is sufficiently tight. Well that was the issue. The triangles were lined up perfect. Problem was is the seal under the cap wasn't fulling mating with the surface (all the time) and was the source of the small air leak. The engine pulls a vacuum and was getting a little air from the oil cap. Had I tighten it like normal and not lined the triangles up, I would have never had then lean codes/engine running rough.

Local shop pressurized the engine via the intake with smoke of some sort and saw it coming out of the oil cap area. A new oil cap solved the problem. go figure.....

 

I have the same problem of a rough engine after the oil change.
Codes P0171 and P0173.
I'm going to buy a new oil filler cap today from Mercedes (7 Euros) and hope my problem will be solved.

 

I noticed a long time ago that these engines will idle just fine UNTIL you remove the oil cap - then they sputter and surge. It is OBVIOUS that the oil cap is sealing well when you see THAT.

If your idle speed varies and does NOT get worse when you remove the cap, you probably have a cap that is not sealing well OR you have a massive vacuum leak elsewhere.

 

Very valuable info. It is great when folks follow up and take the time to let everyone know the solution to their problems.

 

Good people,

I realize this is an old thread, but didn't want to start a new one since I seem to have the rough idle and slight sputtering intermittently on my "new" 05 roadster. Happened after I changed the air filters. My son also washed the engine a bit while the cover was off. A friend came over with his scan tool and got the P0170 and P0174 error codes. See below pic I took of his scan tool.


Scan codes after stumbling ixle and sputtering under acceleration.


I will keep reading to see if I missed something from the other posts.

Any thoughts? Don't mind replacing parts, but don't want to do it mindlessly.

Also any decent scan tools out there someone could recommend?

Many thanks, John

 

Do you think he let water get in the intake? If so, that can cause issues.

 

The engine cover is on correctly with no tears in the donut seal?

 

He said he washed the engine when the cover was off, water could get in the MAF.

 

Thanks, guys. I removed the engine cover and refit it. This morning, the check engine light didn't come on. However, it went on on the way home from work even though it ran well. That is my fourth time driving it and I still haven't gotten used to the car to know what is normal. Will need a few weekends to figure it out. Also, since we moved and haven't received our stuff yet, I have none of my tools with me to help me diagnose.

All that said, am thrilled with the car and will get it into tip top shape.

From this list, I gathered it will be good to replace the cam and crank position sensors so have ordered those, but realize they may not be related to this P0170 and P0174 issue. Will need to chase a potential air leak before I look at replacing the MAF. However it turns out, am confident knowing you all are here on the forum. Thanks again.

John

 

There is not much point in replacing parts that are working, buy ONLY Bosch cam and crank sensors and keep them as spares in the car along with the tools to install them if needed.
A spare RCM is advisable as a spare as well.

 

You don't ever want to wash the engine with the Airbox off the car - MHO. This opens up the top end of the motor to potentially serious consequences. BAD JUJU!! If you need to clean the motor with the Airbox off, make sure you have something covering the air intake inlet that seals off any water, soap, whatever from entering the motor's intake.

 

Assuming you actually mean the oil cap on the valve cover, this is why I never take this loose during an oil change. I doubt that the oil cap has been off over 5x since I've owned the car. Once the oil filter element is removed, I pour all the new oil back into the engine using this port. Then I re-install the oil filter element and torque that cap to the 25 N-m (18 ft-lbs) stated in the Service Manual. Never had any issues.

I gotta go look for these triangles!

 

So, if you're getting the same codes as orbit398, and his issue was a loose oil cap, you may want to check out his solution which would be easy to do & of only minor cost. The simple test offered by pizzaguy would confirm this issue.

 

Thanks. Was the first thing I checked, but will have to wait until Saturday to have enough time to dig around. Engine light came on again and is sluggish and sputtering when cold, but seems to run fine once warmed up engine light still on). Will get my tools and scan tool next week so I can delve into this a bit deeper.

Have other issues I also want to address such as getting a second key and getting the key fob buttons to work.

I bought it to have something to do so am not upset. Just frustrating moving, starting new job, no stuff and having a great car that needs a little attention to make it even better.

 

Update -- check engine light and P0171 and P0174 code problem solved. After verified there are no vacuum leaks, I swapped out the MAF sensor for a new one, reconnected the battery and now have a well-running Crossfire. Thanks, all, for your help!

 

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Lets hope this is the final answer! Thanks for coming back to tell us what worked! Many do not... Have FUN!


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