Andres Morejon

2002 E55 with 115k miles. Codes were PO170 and 173. Car was sputtering and undrivable. Replaced MAF and worked for a day and a half, codes came back. Changed all the spark plugs and ran much much better. No codes for a day. Now the 2 codes are back, car is lacking power and stumbles and hard to start sometimes. My searching has considered the CPS but I do not know. Any tips or help is appreciated.

AndreNY

Replaced MAF sensor but P0170 P0173 are still on

If the CEL stays on after you replace the MAF there is a good chance there is a vacuum leak somewhere. You will need to check for vacuum leaks. In one case, a ML-Class we worked on had a vacuum leak by the brake booster. The vacuum helps to add pressure to the brake system. Vacuum on one side of the brake booster diaphragm pulls the brake cylinder when you press the brakes. When there is a crack on the diaphragm or the O-rings of the brake booster, you will hear air hissing sound near the brake pedal. Air is being pulled into the engine and is not being measured by the MAF sensor triggering the P0170 P0173 fault codes.

fabbrisd1

1. Did you replace the "gasket" on the back side of the MAF - which with that heat back there gets hot and brittle ? MB OE part - careful not to drop anything down the throat back there

2. Did you change your air filters - Mann or Hengst 0- equivalent OE = like $35

3. What/where did you source your MAF ? Genuine OE Bosch MAF for real is tricky - easy to get ripped - about $120-$140 ONLY from a reputable source - if a auto parts store knock off money down the drain.

4. Stumbling - air leak (which can be that gasket) - good time to replace fuel filter w/Bosch or Mann ONLY - about $50 - the rest/others are junk - drop 1/2 bottle Stabil Marine Formula (blue) in the tank.

Fotoflame

When you replace that fuel filter, while you're down there, start it up and see if any fuel leaks out of the fuel pump. I just discovered that I had a fuel pump leak that way. It only leaked when the car was running. About one drip every 2-3 seconds. From reading the forum it usually leaks from the top of the can where the fuel is going out and into the fuel filter. I'm getting P0170 and P0173 codes with occasional long cranks. I found this fuel leak after I replaced my MAF. I'm not sure if it will fix my engine codes but I should get better gas mileage!

Andres Morejon

Thanks for all of your responses! Since then i have read the responses, I have gone through 3 Bosch OEM new MAF sensors, got brand new (mann i think) filters, replaced the gasket behind the maf in the intake, and have looked for vacuum leaks but cannot find any. Every time i clear a CEL the same PO 170 and 173 come back 2 or 3 days afterwards. I have no idea what else it can be

Andres Morejon

I will double check the vacuum line to the booster, I have also replaced the fuel filter with a mann filter too. Any help would mean the world. The car is not stumbling and it just seems a little bit lacking on the top end (my dads words). Thanks for any help you can offer!

fabbrisd1

You have been diligent - the good news with your work the driving symptoms have gone away.

If it was me - I would dose the fuel tank with 1/2 $9 bottle of Stabil Marine Fuel Stabilizer (blue bottle any auto parts retailer) - and after erasing codes once or twice after the next 4-5 see if Codes go away.

"

Andres Morejon

Long Update:
Car was still throwing the codes. Took out the intake manifold and found a small whole towards the front. Then committed the sin of taking the top half off (without a hole in it) and merged with the bottom of a sl550 intake (same part number). Siliconed it together and problem remained. Ran a smoke test. Slight smoke from egr (opened plunger?) And from the front plunger of the intake(open again?) And then very very slight smoke from silicon seal and a decent amount from the boooster connection at the back. Does it need to he a pretty big leak to trigger the codes or are the small bits enough? Also, injector o rings are kinda worn and a few don't have the retaining clips. Where is the best place for the clips and can this also cause the codes? Seems to trigger after you go above 3 or 4k rpm. Thanks again!!!

Fotoflame

I finally took care of my P0170 and P0173 issue on my vehicle. A smoke test revealed that there was a leak in the gaskets between the intake manifold and the head. Once those were replaced the codes went away.

The mechanic let me observe the smoke coming out of the gaskets while he was performing the test. It wasn't a lot of smoke so I would say if you see a little smoke it's going to throw a code.

Tall Giraffe

Went through this last year as well, chasing mine for months. My issue was from the intake manifold as well. What made mine confusing was the CEL came immediately after I straight piped and de-cat but in retrospect might have been something to do with back pressure.

Anyway, small leaks can frustratingly still trigger the CEL, if sealed correctly will go away after a few starts. My trouble spots were around the manifold RTV seal at side rear and front vacuum hose that comes from the inside of the manifold. I hope you checked yours for longevity as they rot and crumble. I did a mod with a new hose and male connector to resolve longterm. When I sealed my manifold, I went the extra step of spreading RTV along the outside seam and scraped smooth for an absolute seal. Think icing a cake on the side.

While apart, I cleaned the inside of the manifold, replaced the manifold gasket below, cleaned EGR and replaced seals, cleaned the throttle body, replace that seal as well and checked all vacuum hoses. Wiped my problem out.

I cleaned and lubed my o rings for now. The plastic washer was chipped on a few injectors. Injector rehab kits have o rings and possibly washers or you could check RMeuropean or AZ Autohauz for replacement. Cant help you on clips and not having some indicates someone was there before. They were a puto to clip on again but I think the fuel rail keeps them in place. While a tight space, you can apply the replacement clips while back together (use lubricant to slide on).

Good Luck!