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Thread: Won't Hold An Idle

  1. #1
    Junior Member [deleted]'s Avatar
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    Won't Hold An Idle

    My '93 has been acting funny. It started at wide open throttle, around 4500 rpm, the car would lose total power for a few moments come all the way back on, and repeat until full WO throttle was removed. At first, this would only happen if I was already up to 25-30 mph, it eventually creeped lower in mph to the point that even from a start, I'd have these total losses of power. During this period, the car would still start and allow me to drive it in a more responsible manner. Until recently.

    About two weeks ago, my wife took the car about 40 miles. During that trip she noticed what I described above, but at much lower speeds and throttle openings. When it was time to go 15 minutes later, the car would start, but not stay running. I had the car towed. In my mind, I felt ignition, or fuel pumps. Maybe a vacuum leak... Dealer says there was an EGR fault code (check engine light has been on ever since I bought it. Never given me any problem. I figured it was due to the still original after over 270K miles lower harness which is frayed beyond belief.) So, we replace the EGR, handle a few other non-associated issues while it's in.

    I get it back Thursday (2 days ago) and it's smooth. Starts, a little stubborn though. Kinda like it lacks compression... But it starts and runs. I warm it up and test it at WOT, problem is still present. But it started after a 10 minute break. I parked it for a few hours, drove it 40 miles home after work, no problem. I figure, well I'll baby it until I can diagnose the issue and fix / have it fixed.

    I opt to drive it to work this morning. Stop about 2 miles from work. When I get in to go, it starts, I put it in R and it dies right away...


    Insulators have been covered in depth here. I'm sure we didn't handle that when I replaced the caps and rotors about 10 months ago. I know that is a starting point, but I'd love for the collective wisdom of these pages to discern whether or not the issues I've described here are one and the same with those experienced by other users.

    Thanks in advance.
    Last edited by [deleted]; 2 Weeks Ago at 09:05 AM.

  2. #2
    E500E Guru doolar's Avatar
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    Re: Won't Hold An Idle

    Check codes is the first step I'd say. You say that the dealer did, do you know if he found anything else? But it would be good to know what codes are present now after you replaced the EGR.

    The first gut feeling I get is the NSS. But first step here is to pull the codes!

    Thomas
    1994 E420
    1993 500E - (my fathers)

  3. #3
    Junior Member [deleted]'s Avatar
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    Re: Won't Hold An Idle

    They told me the EGR was the only fault code.

    The car is in a parking lot now, I'm hoping I can go over and start it to get it the last two miles to the dealership. Will know more then, hopefully. I fear that my local master MB techs are woefully under skilled on the older stuff.

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    Re: Won't Hold An Idle

    If lower harness was changed, how about the upper one? Also I would change the insulators as it is well documented. Check and clear codes after insulators are in.
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    199/268
    2014 E350 Cab 799/264

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    Junior Member [deleted]'s Avatar
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    Re: Won't Hold An Idle

    From what I can understand from inspection / previous owners records, it is the top harness that has been replaced. The bottom is in dire need. It's something I've been dying to do, but have been without the space and tools since I purchased the car. I'm now in a space where I'll be able to tackle some projects... For anyone that's done the lower harness, on a scale of 1 - 10, where's this rate. Any good resources out there to start researching this job?

    Insulators are the first things to get swapped. In this forums opinion, are my observances similar to others who have solved their issues with new insulators?

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    E500E Guru doolar's Avatar
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    Re: Won't Hold An Idle

    Quote Originally Posted by [deleted] View Post
    They told me the EGR was the only fault code.

    The car is in a parking lot now, I'm hoping I can go over and start it to get it the last two miles to the dealership. Will know more then, hopefully. I fear that my local master MB techs are woefully under skilled on the older stuff.
    That is sadly often true, they just don't know these cars. Perhaps someone from the US can help you with recommending a good indy shop in Portland, if there's any? That's usually a better option than making the local dealership richer, IMO.

    You could also get a code reader yourself and read the codes. There's plenty of info here on how to do it, not difficult at all, and a simple code blinker box is not expensive.

    nocfn's suggestions are spot on to, if it was my car, I'd start off by checking if the harness has been replaced (the original ones are all bad, but might not cause problems, yet) as well as insulators/rotors/caps. Even if you replaced the caps just 10 months ago, there could be moisture in there. I've had moisture in mine after a week.
    Thomas
    1994 E420
    1993 500E - (my fathers)

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    Re: Won't Hold An Idle

    Lower harness is diy, and if you follow the how-to, you see the simple way to thread it through in 30 minutes. 1 hour tops gets it done.
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    199/268
    2014 E350 Cab 799/264

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  11. #8
    Junior Member [deleted]'s Avatar
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    Re: Won't Hold An Idle

    Well, I went to the car after work hoping it hold an idle... it didn't. Fires, catches, then sputters out. Almost exactly like it's running out of fuel. Spose that should be the next thing I check, eh.

  12. #9
    E500E Guru TerryA's Avatar
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    Re: Won't Hold An Idle

    [deleted]

    Sounds like you need your 500e as a daily driver if not PARK IT. If your car is going to WOT that is a BIG SAFETY ISSUE (actually life threatening issue) and shouldn't be driven until corrected especially by your wife.

    That said don't go off half cocked shotgunning in all directions before you get some expert advise on what codes are coming up. A 500e will break you if just start throwing $$$ at it and keep going to a Mercedes Dealership with your problems.

    You definitely need to find and Indy Tech in Portland area and first get the codes read properly or find out why no codes are showing up. As soon as he spots your post our esteemed leader Gerry VS lived in Portland for around 10 years and I'm sure he will be able to recommend a good Indy Tech for you. You could try sending him a PM.

    You can get great advise on our forum but as you have already seen they need codes to send you in the right direction. There is a built in blink code button on the firewall in the engine compartment that will help. I believe there are instructions on it's use somewhere in the "How To" thread.

    Good Luck & Be Safe
    Terry

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    Re: Won't Hold An Idle

    Thank you.

    FYI, I put it to WOT. The car doesn't intermittently just go there. I'm sorry if I wasn't clear. It has been my daily for the last 18 months, but I do have several other cars to select from, luckily.

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    Re: Won't Hold An Idle

    What is the date code on the ETA, and do you have a spare E-GAS module to test with?

    Also, "EGR was the only code" sounds fishy to me. Did they check ALL SIX powertrain computers, or just the DM? The DM is what triggers the CEL, but there can be many other codes on the other 5 modules with no CEL.

    Dave M.
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    1994 E420 (Blondie)
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  18. #12
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    Re: Won't Hold An Idle

    Back in the garage... how's this plug color look?
    Attached Images Attached Images

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    Re: Won't Hold An Idle

    Quote Originally Posted by [deleted] View Post
    Back in the garage... how's this plug color look?
    Can't see the insulator very well, but that does look a bit darker than normal. However, if the last time the engine was running it was a cold start and moved from the parking lot to the garage, they could be darker than usual.

    Photos below of 'normal' used plugs.

    Attached Images Attached Images
    Dave M.
    1997 E420 (Bugeyes)
    1994 E420 (Blondie)
    1994 E500 (Q-ship)
    1992 500E (Mach 5)
    1987 300D (Sportline Stage 2)
    Click here for my website
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  22. #14
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    Re: Won't Hold An Idle

    Seemed a little dark. But, there were multiple cold starts prior to this pic.

    So, the cap and rotor were still looking perfect. Also, back of the insulatir is clean, and mostly dry. In fact, it looks like it was replaced with the cap and rotors. The guy I had do the work knows these motors pretty well... this was a nice surprise.
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    Re: Won't Hold An Idle

    What brand is a gold insulator?
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    199/268
    2014 E350 Cab 799/264

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    Re: Won't Hold An Idle

    Quote Originally Posted by nocfn View Post
    What brand is a gold insulator?
    I think it is black (Doduco brand, OE on older motors) and the color looks funny due to the camera flash.

    I've never seen any insulators besides Bosch (orange) and Doduco (black). Although the OE/dealer caps are Bosch, the OE/dealer rotors are Doduco.


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  28. #17
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    Re: Won't Hold An Idle

    iPhone flash and poor quality caused it to look orange. It's Bosch, or old OEM.

    Fuel pressure sits around 60, some probably excessive leak down, it fires and flutters around 50. Drops pretty sharply and dies at about 20.

    Replace fuel pumps and regulator, methinks...

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  30. #18

    Re: Won't Hold An Idle

    Hello, I am from Portland (currently in the Bay Area) and a former '93 500E owner. There are two good independent shops I can recommend: Burback Motors (503-236-1737) and MBI Motors (503-231-0444). Both shops are well versed in the 1990s era cars and the 500E. I personally went to Burback but both shops are good. Both located in SE Portland. I would be wary of taking a 500E to the dealer -- the techs are not well experienced on these older cars.

    Good luck and keep us posted!

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  32. #19
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    Re: Won't Hold An Idle

    I've heard good things about MBI. I feel like I've heard of Burback...

    So... seemingly the leakdown on the FPR is w/in spec. Leads me to believe the fuel pumps must be at fault.

    this was after 25 minutes. After an hour it had dropped below 40.
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    Re: Won't Hold An Idle

    Quote Originally Posted by [deleted] View Post
    So... seemingly the leakdown on the FPR is w/in spec. Leads me to believe the fuel pumps must be at fault.

    this was after 25 minutes. After an hour it had dropped below 40.
    That mostly confirms the check valves at the pumps are OK. If pressure ever drops below ~40psi while the engine is running, the pumps are likely at fault - replace both with Bosch, not aftermarket.


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    Re: Won't Hold An Idle

    Pumps it is, then... I'll circle back upon completion.

    is there an easy way to do this!?
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    Won't Hold An Idle

    Do not reuse the washers, buy new and consider replacing the fuel hoses as well.
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    199/268
    2014 E350 Cab 799/264

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  37. #23
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    Re: Won't Hold An Idle

    Great advice. In my previous life as a tech, that would have been obvious. I've been pushing paper around for too long.

    Thank you.

  38. #24
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    Re: Won't Hold An Idle

    Quote Originally Posted by Allen_Stephens View Post
    Hello, I am from Portland (currently in the Bay Area) and a former '93 500E owner. There are two good independent shops I can recommend: Burback Motors (503-236-1737) and MBI Motors (503-231-0444). Both shops are well versed in the 1990s era cars and the 500E. I personally went to Burback but both shops are good. Both located in SE Portland. I would be wary of taking a 500E to the dealer -- the techs are not well experienced on these older cars.

    Good luck and keep us posted!
    I've used MBI at least a half dozen times for things that I did not feel like doing myself. I have never used Burback. MBI will install customer parts. Burback will not install customer supplied parts. MBI has loaner cars. I don't know if Burback does.

    1992 500E
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  40. #25
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    Re: Won't Hold An Idle

    I’d replace the fuel filter while you’re in there too if it’s not done recently.
    Thomas
    1994 E420
    1993 500E - (my fathers)

  41. #26
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    Re: Won't Hold An Idle

    Quote Originally Posted by [deleted] View Post
    Pumps it is, then... I'll circle back upon completion. is there an easy way to do this!?
    It's straightforward but not easy. If you can't drive the car into reserve to get under 3 gallons in the tank, siphon remaining out of the gas tank (or, drain from the large hose that goes into the first pump). If anything goes wrong, you want as little gasoline as possible in the tank. On a different forum, a guy had his car AND garage burn to the ground due to things going awry during fuel pump/filter service. </PSA>

    New copper seals highly recommended, Klink says to use a THIN coat of the neon green wheel bearing grease on the copper seals.

    Also highly recommended is to replace the high-pressure fuel hose that exits the filter, must buy OE / Genuine MB only, yes it's expensive, no the aftermarket hoses won't last and will be a fire hazard. More info here:
    https://www.500eboard.com/forums/showthread.php?t=8977


  42. #27
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    Re: Won't Hold An Idle

    I’m 80 miles from Full... Doh!

    I’ll read thru the link. Thanks for the info. Will report back.

  43. #28
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    Re: Won't Hold An Idle

    It was a relatively easy swap. Little bit of gas, I didn’t have the main line from the tank adequately pinched, so when I pulled it, I got a little wet. After that, though, smooth as silk. Once I put the car on the ground it fired up and ran like a top! Warmed it up, and did a few pulls, felt great!

    I swapped plugs also. While I was in there, the front cylinder, left side, had some dampness on the threads and in the coil pack... I’m wondering if anyon else has experienced this. I wonder if wet weather has creeped in through the gap in the black cover which allows the wires out, and settled there in that first spark plug access cylinder...?

    Otherwise, a relatively easy job. I’m grateful that I was able to diagnose the problem. I should have trusted my gut, instead of taking it to the dealer. By the way, the EGR valve they replaced kept the check engine light off for a dozen starts, or so. I trust that it needed done, but can’t help but feel I threw that money away...

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