W124 gradually losing power on acceleration - PeachParts Mercedes-Benz Forum

texasgirl3 · #1 06-02-2013, 11:56 PM

1994 E320 wagon--my apologies for the long post--trying to include all relevent details.

Drove fine for 5 hours to Mercedes event yesterday, including 95+mph (up to 110) for 30 miles up Hwy 130 (including only b/c it could be relevant?).
On return (after resting 2 hours), started to hesitate and lose power with accelerating from 65 (for a pass), and over the next 60 miles continued to lose power each time I accelerated (never flooring it, but if going up a slight hill or tried to speed up), each time if I let off the gas a little bit it seemed to go OK for while, but gradually kept hesitating and going slower and slower, again each time I let off the accelerator completely it seemed to regain a fraction more power for a short time. Finally died completely. Was able to restart and get off the road and park it, and tow driver was later able to start and drive onto his truck. This felt the whole time like a fuel problem.

RPMs were always steady--no racing. Car temp normal (outside 90+ degrees). Oil pressure normal. No indicator lights. No odd noises. And turning off A/C didn't make any difference.

I was forced to leave at dealership as I was 100mi away from home and my indy mechanic.

This is the third time in <2K miles (10months) the car has behaved exactly this way--the previous times happened when gas tank was in Reserve.

First time the dealer "could not duplicate problem", but replaced OVP and fuel pump relay--report also says "air filer hosing loose, no seal between hosing and mass air flow sensor" and suggested replacing air filter housing (not done due to $$). This first time also happened immediately after Costco here had a bad batch of gas and reimbursed me $1000 to repair damage to my CLK's fuel system (and many other MBs in the area). But dealer insisted the bad gas could not have caused the problem on the E as it has an older, less sensitive fuel system.

Second time dealer said possible clogged fuel filter or screen, but my service advisor suspected likely just debris in gas tank being sucked into fuel system, and advised I just keep tank >1/4 full, which I have done faithfully.

Yesterday never let it get below 1/3 full, so seems unlikely its debris? (ALWAYS buy premium gas)

Looking for advice--don't have a lot of $ to throw at what is not my daily driver. Or short-term fix to get home where I can get fixed cheaper. Tow truck driver suggested C-foam, but friend who is a service advisor at another dealership said to stay away from that.

And still suspicious if it could be related to the bad gas. I never saw/heard exactly what the gas problem was, only that the tanker driver messed up somehow. Costco sent letters to all affected customers, and quickly paid for the repairs, reimbursed me for the gas bought, and gave me a $50 gift card for my trouble. Later saw them emptying out the underground gas tank.

If you got this far, thanks for reading! :-)

Gilly · #2 06-03-2013, 04:18 PM

HAH piece of cake (the reading part anyways)

Sounds an awful lot like a plugged catalytic converter. Cheap to test, but noisey, you would loosen the header pipe from the exhaust manifold, you want to be careful not to let fumes build up in the interior when you do this. Only makes sense to do it if it actually is acting up.

hookedon210s · #3 06-03-2013, 07:59 PM

Equally long-winded answer follows: Don't let them convince you that the CLK fuel injection system is more delicate than the system found on your E320. I bet your problem is caused by the contaminated gas. Years ago we had a fuel injected shop car (280TE Euro) that was fueled with contaminated gas containing a fine white powder. Repair costs were $$$ due to having to clean/replace the entire fuel system a couple of times. The powder was so fine it bypassed the main filter and the non-replaceable filters in the warm up regulator and injectors and coated the insides of the entire fuel system including the hoses and lines.

My guess is you have a particulate type contamination that gets stirred up the longer your vehicle is operating and may be large enough to temporarily plug the in tank fuel filter. Once the car is shut down for a bit it settles down, the in tank filter unclogs and your car will operate normally for a time. I would contact whoever performed the repairs on your CLK to determine exactly what kind of contamination was found in your CLK's fuel system. Whatever it was it's a pretty good bet that that is your problem. Now the bad news---since the problem occurs only after an extended period of operation you will probably be the only one to diagnose whether the fault is fuel pressure related. If you feel comfortable doing this obtain a fuel pressure gauge and check the fuel pressure when the car is running properly and then keep the fuel pressure gauge in the car with you (detached from the fuel rail) and connect it when the problem recurs and observe the fuel pressure to see if it is substantially reduced/at 0 psi. If so, your problem should be solved by draining the the fuel tank and replacing the fuel tank filter and main paper fuel filter. You may also need to have the tank removed and professionally cleaned.

Now the obvious and not so obvious warnings: Proceed at your own risk. Don't do this if you are not competent to safely carry out these tests. Gasoline fires can quickly ruin your life. Have the proper fire extinguisher handy and know how to use it. Operating your car for an extended period of time with a fuel pressure gauge connected is a fire hazard and never operate your car with the fuel pressure gauge in the passenger compartment. Also, the fuel rail will/may have gasoline under pressure when you connect the fuel pressure gauge so gasoline WILL leak or spray when you attempt connect the gauge. Wear eye protection, wrap the schrader valve connection and gauge hose with a rag and connect quickly.

Good luck. Mark

texasgirl3 · #4 06-04-2013, 03:31 PM

Thanks Mark! What you say sounds very logical--and my gut kept telling me it didn't make sense that I never had this problem until right after buying the bad gas (put gas in both cars on the same day). Talked to the other dealer in town and they just said they didn't see cars like mine have this problem--only newer ones. Well there aren't that many on the road anymore and most owners probably don't take them to the dealer--my indy mechanic didn't know anything about the contamination until I told him.

Maybe I will see if dealer can run this pressure test--not sure I feel comfortable doing it myself.

Either that or if its driving again now (after sitting a few days), drive it home to my indy mechanic to do.

Renate

duxthe1 · #5 06-04-2013, 08:35 PM

With that set of symptoms, I'd be very suspicious of the fuel pump itself. With the engine falling off during higher demands and recovering during lower demands it sounds as if the pump is barely putting out enough volume and pressure to run the engine.

pawoSD · #6 06-04-2013, 08:38 PM

Are the pumps noisy? They should be very quiet if healthy. Could also be a plugged fuel filter especially if bad fuel has been run through it.

colincoon · #7 06-04-2013, 08:52 PM

Did you check the tank vent? If its plugged this could cause your problem.

hookedon210s · #8 06-04-2013, 09:25 PM

How much time has passed since the Costco issue? Since Costco is very good on customer service, is insured for events like this, will hold the negligent transporter liable for any damages and has a record of your purchasing gas on "bad gas delivery day", I would contact Costco about your problem and tell them that you are taking your car to the dealer or competent indy to diagnose the problem at Costco's expense. Be sure to tell them when the problem started and that it is a dangerous situation with the car stalling, etc. Then get the dealer/indy on board to truly diagnose the problem instead of telling you to keep the gas tank full, the contamination doesn't affect "old" cars like yours, and other nonsense. In fact your fuel system may be more delicate than a newer system in that it pumps excess fuel to the fuel rail and returns the excess to the tank essentially circulating contaminants that aren't trapped in the various filters over and over again offering multiple opportunities, if you will, to clog the system. Be sure the dealer documents what they find. It may be that one of your fuel pumps is failing due to mileage/age but it is a simple matter for the dealer to pull the tank screen to check whether it is plugged with crap (have to drain and collect the gas in the tank when this tank screen is pulled) and the main fuel filter to check whether it is restricted. Surprised they haven't done this yet---either they are too busy with other gravy jobs, incompetent or just don't want to work on older vehicles. Mark