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Thread: 1994 E500E - Unresolved Misfiring [Pulled Codes]

  1. #1
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    1994 E500E - Unresolved Misfiring [Pulled Codes]

    Hello all! Longtime lurker, first time poster.

    I have a 94' e500 with 110k miles on the clock that could use your help. It has an updated upper wiring harness, original lower harness.

    Over the past month or so I've been experiencing an issue with an engine misfire while driving. The vehicle would be at cruise (say 45mph) at light throttle to maintain speed and the engine would suddenly feel lean for just a moment and then return to normal. Over the course of a month this issue manifested into a more prominent but momentary "blip" in power, and now to a rather severe lurch while at partial throttle. Heavy or WOT the car pulls fine. So I don't it's a fuel starvation issue.

    I started with the usual suspects: caps, rotors, plug wires, and plugs. I installed new bosch caps & rotors, and F8dc4's. The insulators are original but in fine condition. The wires had already been replaced by the PO with Bremi wires. All appear and feel new, though in typing this I just realized I haven't actually checked their resistances. No improvement with the issue after the above changes.

    Next I suspected the ETA. It's original to the car (93' production date), so I replaced it with a shelved unit that I picked up from a junkyard a year or so ago. It's an old unit as well, but since I had it on the shelf I figured I'd try it out. Once installed and calibrated, I test drove the car. No change in run quality (though it does rev' a bit higher on startup which is neat). I replaced the throttle body boot and the the PCV hoses during the change too.

    So next I did what I should have done from the start and pulled the codes. This was new for me, as I've only ever used the DM module LED blinker. This time I tried out the HFMscan software/ adapter to pull the codes across all the modules. Two codes were stored: 004; and 010. I've paste'd the readout below:

    004, Post
    4 Voltage at air mass sensor with hot wire.
    Voltage too large/small or ground cable at air mass sensor
    open circuit. (The fault may be ignored on vehicles up to 07/91)
    Verify voltage at air mass sensor with hot wire.
    While IGNITION=ON = 1,0-1,2 V - ENGINE=IDELING = 1,3-1,7 V.
    Verify also the ground cable for sensor. (While IGNITION=OFF < 6 Ohm)
    __________________________________________________ ___________
    010, Post
    10 Idle speed recognition from electronic accelerator pedal faulty.
    Control unit has short circuit.
    Verify idle speed recognition signal voltage from EA pedal actuator.
    While IGNITION=ON, and accelerator in idling position < 4,8 V
    While IGNITION=ON, and accelerator in full throttle position > 5,5 V
    On vehicles up to 7/91 fault may be displayed although no fault exists.


    Looks like a fault with the MAF sensor, and what I believe is the momentary switch above the pedal? I think I saw another post on here about an issue with that. I'm new with HFMscan, but I'm pretty sure it pulls fault codes from all modules right? Not just the diag module.

    Before I throw more parts at my problems, what do you guys think?

    I did try driving around with the MAF unplugged. But I experienced the same issue.

    Open to all thoughts and criticisms lol. Thanks!
    1995 E320 - 1988 300CE - 1993 400E - 1987 300D - 1987 300D - 1984 500SEC - 1985 500SEC - 1986 190E 2.3-16V EFI - 1987 300TD - 1994 E500E

  2. #2
    .036 Hoonigan™
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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    Quote Originally Posted by CRodgers View Post
    So next I did what I should have done from the start and pulled the codes. This was new for me, as I've only ever used the DM module LED blinker. This time I tried out the HFMscan software/ adapter to pull the codes across all the modules. Two codes were stored: 004; and 010. I've paste'd the readout below:
    Minor clarification... HFM Scan for LH will only pull codes from the LH module. AFAIK, it can not pull codes from all 6 powertrain modules. You need a hand-held blinker box, or MB-specific digital scanner (Star/SDS), to check the other modules. More info in the "sticky" posts in the DeCoding forum at this link.

    Anyway, code #4 does make the MAF appear to be suspect. However, first clear that code and see if it comes back. It could be a phantom code from aeons ago. And the fact that driving with the MAF unplugged doesn't change anything, makes me thing the MAF could be a red herring.

    Code 10 may be related to your ETA replacement. The throttle linkage is very, very picky about being set up just right.

    Total wild guessing here, but the one time I encountered something similar to what you describe, it ended up being a vacuum leak due to a deteriorated rubber hose elbow. I'd start by chasing down every vacuum tube under the hood (there are only a half-dozen total) and verifying everything is intact and holding vacuum. A smoke machine might speed up the process if you have one.

    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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  3. #3
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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    Quote Originally Posted by gsxr View Post
    Minor clarification... HFM Scan for LH will only pull codes from the LH module. AFAIK, it can not pull codes from all 6 powertrain modules. You need a hand-held blinker box, or MB-specific digital scanner (Star/SDS), to check the other modules. More info in the "sticky" posts in the DeCoding forum at this link.

    Anyway, code #4 does make the MAF appear to be suspect. However, first clear that code and see if it comes back. It could be a phantom code from aeons ago. And the fact that driving with the MAF unplugged doesn't change anything, makes me thing the MAF could be a red herring.

    Code 10 may be related to your ETA replacement. The throttle linkage is very, very picky about being set up just right.

    Total wild guessing here, but the one time I encountered something similar to what you describe, it ended up being a vacuum leak due to a deteriorated rubber hose elbow. I'd start by chasing down every vacuum tube under the hood (there are only a half-dozen total) and verifying everything is intact and holding vacuum. A smoke machine might speed up the process if you have one.


    Thanks for the info GSXR!

    I finally got around to putting a DTC code reader together. Pulled the codes and cleared those that I could. Results are as follows:

    Pin4 - LH Fuel Injection Module - error code:

    • 4; voltage at hot wire MAF sensore insufficient, or too high, or open circuit in ground wire at hot wire MAF sensor

    I tried clearing this code, but it persisted.

    Pin6 - ABS & ASR - error codes:

    • 13; stop lamp switch
    • 21; ABS/ASR hydraulic unit, pressure switch
    • 32; CAN data bus to DI module interrupted

    All codes cleared

    Pin7 - EA/CC/ISC - error code:

    • 5; Stop lamp switch

    Code would not clear

    Pin8- Base Module - Error code:

    • 5; Module box max temp exceeded

    Code cleared

    Pin16 - HVAC Control Unit - Error code:

    • 30; Circulation Pump short circuit/interupt

    Could not clear code. I checked the pump and found that the motor housing was burning hot. Significantly hotter than the coolant temp. So there may actually be a short there. I unplugged it for the time being. I'll swap it out.

    Pin17 - EZL - No error codes

    Pin19 - DM

    • 10; Voltage at MAF sensor too high/low.

    Could not clear code.

    Pin30 - SRS

    • 5; Front drivers seat belt buckle switch. (Oh lawd, gonna have to scrap the car now.)

    Code would not clear

    I need to do some more reading, but I doubt the brake switch would affect fueling or spark. Could maybe affect ASR. So I'm squinting harder at the MAF right now. Any thoughts? My dad has a 400e that I'm thinking of borrowing the MAF from.

    I'll also note that the lower harness is original, and is shedding insulation like snake skin. I haven't read about them causing drivability issues like this since it mainly supports the charging system. But perhaps I'm completely overlooking that.



    1995 E320 - 1988 300CE - 1993 400E - 1987 300D - 1987 300D - 1984 500SEC - 1985 500SEC - 1986 190E 2.3-16V EFI - 1987 300TD - 1994 E500E

  4. #4
    .036 Hoonigan™
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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    With all the powertrain codes cleared, drive the car until it hiccups again... then pull codes and see what popped back up. Most of the above are junk/phantom codes that I wouldn't worry about, but if the MAF codes return, definitely borrow your dad's MAF to swap out and see if your issue goes away (and if the glitches move to his 400E).

    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
    Click here for my YouTube channel

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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    I actually was not able to get the MAF codes to clear. I followed the clearing procedure, then held for another 2-3sec to confirm that it had been cleared, but the MAF codes remained.
    This afternoon I swapped out the MAF sensors. My sensor didn't have any ill effect on the 400e. I didn't bring the code reader with me so I didn't check for a new code on the 400e. I still brought the 400e's MAF home and popped it in. Sure enough the open circuit MAF codes went away and there is a significant improvement in throttle response. I thought that was the ticket, but the same blip in power came back on a short test drive.

    While the MAF sensor evidently is due for replacement, something else is still going on. But at least I'm code free at this point. The car thinks its running great lol. I've attached a link of a short clip below that better shows what it's doing. In the video I'm in park idling. But the blips in the RPM's shown in the video translate to some serious bucking while on the road. It truly feels like the car is dropping down a gear.

    Link: https://photos.app.goo.gl/teePArfjqxZHKtyt7

    I'm suspecting something back on the ignition end of things. I have new plugs, wires, caps, and rotors. All bosch. The only thing original in that equation is are the insulator discs. Wondering if there's a crack thats allowing an arc to the cylinder head. Should have grabbed those too from the 400 lol. At least my dad is happy though, he gets a new MAF boot since I broke his old vulcanized one removing the MAF
    Last edited by CRodgers; 08-04-2018 at 01:25 PM. Reason: Typo
    1995 E320 - 1988 300CE - 1993 400E - 1987 300D - 1987 300D - 1984 500SEC - 1985 500SEC - 1986 190E 2.3-16V EFI - 1987 300TD - 1994 E500E

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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    Update on this. I've bought a replacement MAF sensor which cleared the code MAF code on the LH module and DM module. Also checks out the insulators again. They look brand spanking new.

    I'm not really sure where to go from here other than to throw parts at it. Any suggestions?
    1995 E320 - 1988 300CE - 1993 400E - 1987 300D - 1987 300D - 1984 500SEC - 1985 500SEC - 1986 190E 2.3-16V EFI - 1987 300TD - 1994 E500E

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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    Didnt read the whole thread, but have you verified the spark plug wires are screwed in tight to the suppressors?
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

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

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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    Thanks for suggestion nocfn!
    Sorry, probably overkill with the info in my first post. By suppressor, do you mean the insulator posts on the caps? I have confirmed that all the plug wires are fully seated on the posts. I'll double check and make sure the coil wire are seated properly as well. I'm wondering if maybe I should be looking a little harder at the coils at this point. Wild guesses though lol. I may take it to an indy mechanic local to me soon to see if we can get some more clues from an SDS.
    1995 E320 - 1988 300CE - 1993 400E - 1987 300D - 1987 300D - 1984 500SEC - 1985 500SEC - 1986 190E 2.3-16V EFI - 1987 300TD - 1994 E500E

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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    I had a misfiring problem that turned out to be a bad suppressor/resistor spark plug boot.

    Measure resistance from the cap to the end of the spark plug boot. Should be around 2,000 ohms.

    However, after reviewing your video, the above is only a guess. My symptoms were more pronounced under load.

    If Jono, Klink, or GSXR review this video, they will know the answer.
    Last edited by Trae; 08-26-2018 at 06:35 PM.
    Trae
    1992 500E Renntech
    1993 500E
    1990 560SEC/ 2001 SL500
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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    I just realized this was a video link: https://photos.app.goo.gl/teePArfjqxZHKtyt7



    The issue is around the 1:00 mark. That looks like a throttle oscillation to me, not a misfire. Have any codes returned? If there are no codes, the next items I'd want to see are in the live data via SDS. I'd also check for a vacuum leak - probably a big one. Your idle RPM is way high. At 90C, you should never have a 900rpm idle. Normal is 650rpm in P or N, and 500rpm in gear.


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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    you are not alone on that link. Halfway thru it the video shut off to render audio for me. Some reason the Surface I use tends to be viewed as a hand held mobile device by these forums, same with a 27" all in one PC.
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

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

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    Re: 1994 E500E - Unresolved Misfiring [Pulled Codes]

    Thanks for the input guys. And sorry for the intermittent responses.
    NOCFN - I'll check the resistance at the wires thanks.

    Youtube was taking forever to process the video so I used google photos. I'm guessing it doesn't play nice with mobile devices. Here's a link to youtube for those having issues:
    GSXR - If it makes a difference, I had just restarted the vehicle a few seconds before beginning the video. Typically the rpm is slower in park than what you're seeing. Since it was already at operating temp though after restarting, should it actually drop rpms immediately after start? I assumed it's supposed to start high and then modulate down regardless of coolant/ambient temp. Sounds like that may not be the case. No codes are present now. As for vacuum leaks, the only one I've found was a line to the secondary air injection pump had popped off. It was making a puttering sound for a little while before I dug into it. Its back on now though. I might try smoking the intake plenum and see if anything serious pops up. Need to visit a friend to do that.

    I'll ask around to see if any enthusiasts have access to an sds. I've I uploaded a data log file, would you find that helpful?

    1995 E320 - 1988 300CE - 1993 400E - 1987 300D - 1987 300D - 1984 500SEC - 1985 500SEC - 1986 190E 2.3-16V EFI - 1987 300TD - 1994 E500E

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