95 S600 Coupe failed emissions - PeachParts Mercedes-Benz Forum

Hatebreed · #1 11-12-2018, 03:21 PM

Ok, Just got this S600. I paid very little for the car. This is the only reason I even entertained this purchase. The PO reported that the car did not run and was losing all of its fluid. I bought not running the car and it is in excellent condition. Repaired the coolant leak from behind the engine and it run really well. It drives great on the highway and does not stall or even run rough. The only issue is it failed emissions at idle. The idle seems to hunt very slightly and I have a fuel smell from the exhaust....hence the failed emissions. Any ideas on this one? I am more of a diesel person and this car has considerably more going on. Also, I have no check engine light. The rest of the stuff actually works...ASR, some weird shock thing, all the bells and whistles all function. My first guess would be the easy stuff oxygen sensor, MAF sensor.... but I would think I would get some type of light? Any ideas?

sixto · #2 11-12-2018, 07:39 PM

I read that throttle actuators can go bad. I don’t know if that will mess with idle or throw a CEL.

Has the wiring harness been replaced?

Sixto
98 E320s sedan and wagon
02 C320 wagon

Hatebreed · #3 11-12-2018, 07:53 PM

Yeah, that’s what I have been reading as well. I was messing with the throttle body a bit and I managed to get it to throw a ASR code. My guess is from a miscompare from left to right. So the system is working. I am going to pull a plug from the night and left bank and see if I can narrow it down a bit. The exhaust smells like raw fuel. It’s still running well with little indication of an issue outside of the smell. The ASR code went away after I restarted it. I am really appreciating my 300SDL right now. LOL.

jhodg5ck · #4 11-13-2018, 10:16 AM

You need to inspect the wiring @ the actuators, upper harness and the leads coming off of the MAF's. All of this will fail...Did it All on our 94 w/ 35K miles a few years ago. Also, be sure to pull the caps and rotors and give a close look for any carbon tracing. These like to burn up their insulators Behind the rotor and arc through to the block. Causes all manner of Fun.

I like to smoke the intakes on these looking for leaks, unmetered air will through the mixture into a tizzy.
I'd also just 2X check and make sure the cat's are there just for fun...wouldn't be the first time I'd seen an M120 sans cats after they failed from poor running.

Awesome, Awesome car but staying ahead of her/keeping on top of things is going to make owning a Fleet of SD's look like a nap;-)

jono

gsxr · #5 11-13-2018, 02:15 PM

Quote:

Originally Posted by Hatebreed

Yeah, that’s what I have been reading as well. I was messing with the throttle body a bit and I managed to get it to throw a ASR code. My guess is from a miscompare from left to right. So the system is working. I am going to pull a plug from the night and left bank and see if I can narrow it down a bit. The exhaust smells like raw fuel. It’s still running well with little indication of an issue outside of the smell. The ASR code went away after I restarted it. I am really appreciating my 300SDL right now. LOL.

You're going to need to pull codes to help diagnose this without throwing money at it. More specifically, clear all existing codes (don't bother writing them down - likely will be a zillion from many years past), verify codes are cleared, drive the car a bit, then check what new codes appear quickly. A hand-held blink code reader will get you the basics.

The fuel smell is a mixture issue, could be related to MAF's, O2 sensors, or LH modules. Assuming the cats are present and original, it's hard to diagnose without live data, which requires a digital scanner (Star/SDS, Snap-On MT2500 with MB kit, or similar).

Jono is right, start by checking the MAF wiring and the rest of the upper harness, and a smoke test would be a good idea as well.

Hatebreed · #6 11-13-2018, 03:37 PM

Guys I really appreciate the feedback. I will definitely get some type of code reader. I was able to isolate this to the RH bank of cylinders. They are all black and show signs of fouling, while the LH side is clean/normal looking. I will do an inspection of the MAF and actuator wiring tonight. My understanding from reading is that the left MAF controls the RH bank of cylinders? Is it normal to have codes without having a engine light?

jhodg5ck · #7 11-13-2018, 04:11 PM

Quote:

Originally Posted by Hatebreed

Guys I really appreciate the feedback. I will definitely get some type of code reader. I was able to isolate this to the RH bank of cylinders. They are all black and show signs of fouling, while the LH side is clean/normal looking. I will do an inspection of the MAF and actuator wiring tonight. My understanding from reading is that the left MAF controls the RH bank of cylinders? Is it normal to have codes without having a engine light?

Codes can move you up a step or two but these things can ghost you to death with codes...ask me how I know

SDS/HHT and a good DVOM coupled with your wiring diagram will prove to he priceless when diagnosing early 140's.

Jono

Sent from my SM-G960U using Tapatalk

gsxr · #8 11-13-2018, 04:29 PM

I'm not sure about right vs left controls, as I've never owned a V12.

The CEL only illuminates for emissions-related faults. It's possible to have component failures where the computers don't realize emissions are being affected. And, also possible to have the engine running terribly but never trigger a CEL because there's nothing faulty with emissions stuffs.

I don't have a 140 + M120 diagnostic document, but this one for the 140 + M119 will cover quite a few of the various systems except for the engine:
http://www.w124performance.com/docs/mb/diagnostics/DTC_List_W140_M119_1992-95.pdf

And, this factory DTC manual will cover what you need for the M120:
http://www.w124performance.com/docs/mb/diagnostics/DTC_Reference_Guide_Ed.B.pdf

If the wires to your MAF's are disintegrating (I assume you've read up on the biodegradeable insulation problem), fix that first.

gsxr · #9 11-13-2018, 04:34 PM

Almost forgot - the online diagnostic manuals will be a huge help, once you learn how to navigate them. And, they include the DTC's which may be easier than poking through the big PDF... or not:
http://manual.startekinfo.com/manual/JSP/sitemap.jsp

Jono is right, you could chase ghost codes if the wiring is hosed. Live data is a huuuge help but you need to know what you're looking at. On the M120 this can be a bit easier as you can compare left bank readings to right bank and see if anything is drastically different.

Hatebreed · #10 11-14-2018, 06:21 AM

Quote:

Originally Posted by gsxr

Almost forgot - the online diagnostic manuals will be a huge help, once you learn how to navigate them. And, they include the DTC's which may be easier than poking through the big PDF... or not:
STAR TekInfo

Jono is right, you could chase ghost codes if the wiring is hosed. Live data is a huuuge help but you need to know what you're looking at. On the M120 this can be a bit easier as you can compare left bank readings to right bank and see if anything is drastically different.

Thank you guys for all the information! This car is a beast on the road. I am probably going have to slow down before I get arrested. I have a code reader coming and I am looking into the live feed option. Really appreciate the links.....I am super excited about digging into this thing..

gsxr · #11 11-14-2018, 10:56 AM

If you are seriously interested in live data, I'd strongly recommend a Star / SDS Compact C3 setup. Probably ~$500 including a used IBM or Dell laptop for the internal HDD option and native serial port. Lots of threads on this topic.

Here's a good one... you'll need to copy/paste and replace the asterisks with "500E board", minus the space. If you click the link, you'll get an error like "page can’t be displayed", 404, etc:

Exploring the MB STAR C3 (SDS)
https://www.*********.com/forums/showthread.php?t=2651

anziani · #12 11-14-2018, 11:49 AM

hatebreed, definitely take a hard look at a Star system or pay your dealer to scan your engine. Most decent indies also have the Star scanner.
I bought my '97 CL600 a couple of years ago. It is the finest and last car I will ever own. And you're right about the speed and power. I had mine up to 145MPH and it was barely breathing hard! And I've had little if any problems outside normal maintenance items. Did I understand you right in that you have no CE light? or has it been disconnected? These are very complex cars and I would suggest you find a GOOD indie to help you.
Anziani
'97 CL600 68K

sixto · #13 11-14-2018, 03:21 PM

Does a ‘95 S600 blink actionable codes with an LED at the X-11 port?

Sixto
98 E320s sedan and wagon
02 C320 wagon

gsxr · #14 11-14-2018, 03:23 PM

There should be a built-in LED and button, however this ONLY displays blink codes from the DM (Diagnostic Module), which only has codes related to the CEL. If the CEL is not illuminated (and the bulb in the cluster is good), there are probably no codes here. Even if codes are present, the important ones will be on the two LH modules, two E-GAS modules, two EZL's, and ASR module. A hand-held blinker box (or, SDS) is needed to view & clear codes from all those other modules.

Hatebreed · #15 11-15-2018, 05:36 AM

Quote:

Originally Posted by gsxr

If you are seriously interested in live data, I'd strongly recommend a Star / SDS Compact C3 setup. Probably ~$500 including a used IBM or Dell laptop for the internal HDD option and native serial port. Lots of threads on this topic.

Here's a good one... you'll need to copy/paste and replace the asterisks with "500E board", minus the space. If you click the link, you'll get an error like "page can’t be displayed", 404, etc:

Exploring the MB STAR C3 (SDS)
https://www.*********.com/forums/showthread.php?t=2651

Cool thank you! , Checking it out now.