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2006 S350;2016 GLC 300
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Discussion Starter #1
I couldn't find a DIY for this. Also, what tools would be needed?

I'm still trying to resolve my P0170 and P0173 CEL codes!!!

Thanks!
 

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1990 Mercedes-Benz 420 SEL(RIP),1997 Mercedes-Benz E420
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Note: this may/may not repair codes as I am not sure what the codes stated specifically mean.

Courtesy of alldata.com
Fuel Pressure at Closed Throttle
With Vacuum 3.2 - 3.6 bar
Without Vacuum 3.7 - 4.2 bar

Fuel Rest Pressure
Note: After more than 30 minutes. 2.5 bar
Note: Minimum

I would also recommend taking a look at youtube's videos regarding this, there are tons of them all over the site.
 

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If you do a search, someone found a basic little pressure gauge that threaded onto the rail, it was under $20 IIRC.

Do you have a comprehensive thread regarding your codes that lists all the details and what you've done to try and eliminate them?
 

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E320/E250 Bluetec Ford F350 6.7l
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Good find Brandon on that adapter part number.
The adapter is hard to find and at least one member put a Tee on the hose at the fuel pump for testing purpose. Sure having the adapter is much easier.
 

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Discussion Starter #5 (Edited)
Hi Greg. Yes. I joined someone else's thread with the same/similar problem.

http://www.benzworld.org/forums/w210-e-class/1658151-problems-codes-2.html#post5306600

Brief background: CEL light came on. Scanned for codes:
P2017 Self-adaptation of mixture formation to limit value of engine control module (P0170) at idle speed.
P2086 Self-adaptation from the mixture forming (left engine) (P0173)

Other errors (not related to above):
B1439 (Central locking secure time to long. air capacity to high) - Other PSE errors too.
B1217 Rain Sensor


Here's what I've done so far:
- Checked for leaks in vacuum hoses. Found no leaks.
- Replaced MAF sensor with genuine Bosch sensor
- Replaced Air Filter
- Replaced Fuel Filter
- Replaced Transmission connector plug. Trace of oil on the plug. It wasn't leaking on the ground or going up the cable to the control module though.
- Last week, code P200F Right O2-probe before KAT (P0130) came up. So I replaced all four O2 sensors. The error code P200F now gone.
- Erased all codes
- Reset ME Adaptation
- Reset transmission adaptation
- I double checked the status of the transmission connect plug. A very small trace of oil on the plug, but nothing on the pins/wires.

P0170/P0173 keeps coming back. The engine at times seems a little rough, but it's not bad. Maybe I'm being picky. I don't know. I would think the slight roughness is probably caused by whatever is tripping the error codes. I'm getting 25.5-27.5 highway MPG, so it's not eating gas too aggressively.

Other work done to the car (not associated with this problem):
- Replaced the motor mounts
- Replaced the transmission mount
- Replaced the rear flex disc
- Replaced the differential fluid
- Replaced transmission fluid, gaskets, filter
- Front headlamps - Crystal view to remove foggy/yellow finish
- Replaced serpentine belt, idler pulley, tensioner pulley
- All wheel alignment (by dealer)

I spent hours researching the potential causals of this P0170/P0173 issue. I found many potential causals:

• Ignition coils
• Cam and crank sensors
• Oil sensor for leakage contributing to oil intrusion in wiring harness
• Defective fuel pressure regulator
• Leaking camshaft adjuster solenoids
• Crank case vent hose located under the intake manifold. It should be checked for leaks/cracking and also operation of check valve in the hose. The check valve should flow only one way.
• Check fuel pressure and ensure that there are no leaks at the regulator internally or externally
• Make sure there are no vacuum leaks at the intake manifold gaskets or tears in the air supply hose
• Intake air leaks
• Injector defects or carbon build-up,
• Air Flow Sensor defects
• Pressure regulator defects, such as a blown diaphragm
• Fuel tank purge control valve defects or EVAP system leaks
• EGR defects
o EGR pipe clogged?
• Vacuum leaks of any kind.
• Mechanical engine wear, such as, chipped valves or leaking rings.
• Weak fuel pump
• clogged or leaking injectors

The car seems to run fine. No stalling, etc. The only issue is that (perceived) rough idle every now and then.
 

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Discussion Starter #6 (Edited)
Brandon, what is the diaphragm pressure regulator that is referenced above? I can't find it in EPC anywhere.

I assume those values in the chart are good the E320 2001 W210?

Thanks.
 

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Discussion Starter #7 (Edited)

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E320/E250 Bluetec Ford F350 6.7l
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Brandon posted that residual pressure should hold for 30 minutes at 2.5 bars min.
You have pressure leaking somewhere, Leaky injectors would flood the engine and made it hard to start hot. When this is not happening, that means the check valve is bad.
 

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Discussion Starter #10 (Edited)
Goes to show how much I don't know. The check valve you are talking about is the one in the fuel pump? Does the entire fuel pump need to be replaced for that? thanks again! The funny thing is that I don't have any problem starting the car, stalling, etc.
 

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I think it is attached to fuel pump, but I don't drive gasoline for years, so loose touch with details. I would call knowledgeable parts supplier and ask or maybe one of professional technicians on the forum will answer.
 

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Discussion Starter #12
Hmmm....I found a crack in the vacuum hose connecting the pressure sensor (0115420617) and intake manifold. So, I replaced that hose and the one next to it which connects the check valve (0021408460) and intake manifold.

That seemed to resolve the pressure reading at the fuel rail test port. However, I need to run all the tests listed above.

Test #2 says to disconnect the vacuum hose from the diaphram pressure regulator. Would somebody mind identifying what that diaphram pressure regulator is and where it is located? If I had a part number, I could look it up on EPC and look at the diagram.

thanks!
 

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'04 G55 '80 280GE '99 S420 '98 E320 2011 E350 2016 GLA250
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Todd,

You will have to double check with your engine number, but I believe you are like me and have the Pressure Regulator BUILT INTO the Fuel Filter. (One reason why they are on the expensive side...) Here's a pic
 

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Discussion Starter #16 (Edited)
For future refererence, or if anyone is following this thread:

After replacing the two vacuum hoses, I'm now getting rpm surges. Never had that before. It is very noticable when braking to stop - especially between 1000-2000 rpms. A 300-700rpm surge kicks in 2-3 times on its way to idle (around 700rpm). The surge is not very noticable at idle. I also notice the rpm needle move just a tad (lets say 100 rpm) when traveling at high rpms on the highway using cruise control. No addiitional codes. Still have P0170 and P0173.

I've read so many posts and articles about similar symptoms, I'm just about sick. Some thoughts:

1) Vacuum hoses. I already inspected all vacuum hoses (except for the electric change over valve hose - see below) and replaced the suspect hoses. I can order and replace every vacuum hose, vacuum connector, and air hose I can find on EPC. About $75 in parts. Does anyone know how to access the vacuum hose from the electric change over valve (A0025401897) to the intake manifold? This hose routes behind the back of the air pump and up a conduit into the intake manifold. I don't see any way to access the intake end of that hose without ripping out lots of hardware - and I'm not sure which hardware to rip out! One thought. The vacuum hoses I replaced all seem to be the bulk generic vacuum hose (1179970982). Autohausaz says that its a 3.5mm (approx 1/8") inner-diameter hose. I used local parts store hose that was only 7/64" ID hose. Should that be a concern? I know it sounds petty (1/64inch difference), but I'm not going to leave any stone unturned. Finally, maybe I can use a hand-held vacuum pump/gauge to check the pressure of the various vaccum lines. Is there a list of the vacuum lines and what pressure each should have?

2) Take off the EGR valve and a) inspect/clean the EGR exhaust line, b) check the EGR valves. This is probably the top action item on my list.

3) I read a thread where someone had a similar surge issue and it was a cat problem. See post #15. http://www.benzworld.org/forums/w210-e-class/1470358-e320-idle-surge-when-comming-stop-2.html. Is there a way to determine if you have bad cats (front and/or back)? I used a rubber mallet and didn't hear any rattling.

4) Other posts indicate fuel pump and/or fuel filter. The fuel filter was replaced on July 2 with a Mann OEM fuel filter. I don't feel like laying down $200+ for a fuel pump just to see if that fixes the problem. But, the car has 146k miles on it. I've owned it since January (139k miles). The prior service records do not indicate when (or if) the fuel pump was last replaced. I don't think it would be frowned upon to replace it under those conditions. But still, $200+.

5) MAF replaced with original Bosch. I seriously doubt its a bad MAF sensor.

Anyone have any additional thoughts or suggestions? thanks!
 

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It would seem to my Non-Expert opinion that you have an Air Leak somewhere??

I would change out ALL Vacuum lines & Rubbers (go the extra step and securely affix the connections with Tie-Wraps).

You could also get a can of Carburator Cleaner/Starting fluid and spray around the various Intake locales.. see if you get a Jump in RPM's.

It also won't "Hurt" anything, to throw a can of BG 44K into the gas tank.
 

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2010 E350 P1/P2, 2008 S550 Designo, 2002 ML320
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If your fuel pressure is still at 0 when resting then your check valve is shot. It is integral to the fuel pump on your car. I looked through your data (and may have missed it) but are you seeing good, constant fuel pressure when you see these idle issues? For reference, here's my thread on one fix for extended crank, not your issue it seems but there is some cheesy goodness in there on how the fuel pump works and some expected pressures at the rail.

http://www.benzworld.org/forums/w210-e-class/1645448-fuel-pump-extended-crank.html
 

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Discussion Starter #19 (Edited)
Thanks for the response. After I replaced the two vacuum hoses, I didn't seem to have any issues with the fuel pressure at the rail. I saw 58psi with the key is position #2. When the engine turned on, the pressure went to 60psi. After I stopped the engine, I monitored/measured the fuel pressure for 30 minutes. After stopping the engine and removing the key, the pressure was:

9:16pm 58 psi
9:19pm 56 psi
9:22pm 55 psi
9:25pm 54 psi
9:27pm 53 psi
9:31pm 51 psi
9:33pm 49 psi
....from there it dropped 1 psi per minute....after 30 minutes:
9:46pm 36 psi

I'm thinking that the fixed vacuum hose had an affect on the fuel pressure at the rail. Or is it a red herring?

---edit:
I haven't monitored the fuel pressure since the surge doesn't seem to happen at idle and I don't think it would be very safe to put a pressure gauge on the fuel test port and drive the car with it on. I did notice that with the car in park or neutral, if I rev the engine to 2500 rpms or so and let off the gas, it doesn't surge on its way down. I also reset the transmission adaptation. no change.
 

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Discussion Starter #20
I just went out and checked the fuel pressure at the rail. Key in position #2, 58 psi - steady - no needle movement on the pressure gauge. After I start the engine, the needle moves rapidly between 58 and 62 psi. Is that normal? Should the needle remain steady with the engine running at idle?
 
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