Still running rough

[tewfiks]

Okay, I am stumped again. My 95 E420 is running rough again. The check engine light has illuminated again. Checking the code results in 3 "flashes" that indicates the intake temperature sensor. I changed that to no avail. Where do I go from here?

 

[gsxr]

DM code #3 is "Lambda control inoperative".

DM code #9 is "Intake air temperature sensor".

Are you sure it's code 3, and if so, what document indicated code #3 was intake air sensor?

Lambda inop means the LH module isn't happy with something and/or the O2 sensor has issues. You need to pull blink codes from the LH module (pin #4 on the 38-pin socket).


EDIT: LH code #3 is "ECT sensor (B11/2) sensor circuit 2, open/short circuit"... make sure you are checking the correct code translation sheets! B11/2 is the 4-pin Engine Coolant Temp sensor, not intake air...

 

[JC220]

I'm stumped at the lack of information provided by OP

By "Again" what work was done before to get you where you are now PLZ

 

[tewfiks]

Thanks, I will pull codes from the specific socket.
The 420 has both the 38 pin and 8 pin socket.
The resource I used was the one that came with a "code reader" I purchased years ago.
I also noticed the ambient air temperature sensor is loose in the back of the driver's side headlamp housing.
It seems that it is missing something to hold it tight.



I installed an LH module from a 92, shall I revert back to the original units?

By "again" I mean I have replaced: plugs, wires, rotors, rotor caps, engine mounts, air filters, air temperature sensor.....all within the pst 12 months

 

[JC220]

By "again" I mean I have replaced: plugs, wires, rotors, rotor caps, engine mounts, air filters, air temperature sensor.....all within the pst 12 months

Suggest removal of the ignition caps, rotors, brackets and insulators.

Were the insulators renewed?

If not - renew them now and remove all traces of moisture.

 

[gsxr]

Thanks, I will pull codes from the specific socket.

While you are in there, check all 6 powertrain modules, but the LH and T/LLR (for your non-ASR car) are the more important ones.

The 420 has both the 38 pin and 8 pin socket.

The 8-pin setup on the front is only so you can check DM codes to see why the CEL is on, without a hand-held blinker box. Otherwise, that block has no other function whatsoever.

The resource I used was the one that came with a "code reader" I purchased years ago.

Use the PDF file attached at the bottom of this post, nothing else. Most of the lists floating around the interwebs are wrong. I created some directly from the WIS for specific engine/chassis combinations, which is the PDF in that post.

I also noticed the ambient air temperature sensor is loose in the back of the driver's side headlamp housing. It seems that it is missing something to hold it tight.

You may be missing the metal clip, available new, but not cheap. This will have ZERO effect on your engine operation. Tape it in place for now until you can get the proper clip.

I installed an LH module from a 92, shall I revert back to the original units?

It shouldn't matter, but you can swap back for grins. If you didn't reset adaptation on the '92 module before installing, it should have been done, but the system is supposed to adapt either way. Resetting speeds up the process.

 

[gerryvz]

OK, first of all, you NEVER NEVER NEVER use any resource for translating codes for the V-8 W-124 models OTHER THAN the GSXR resource that is attached, or located here:

http://www.w124performance.com/docs/mb/diagnostics/DTC_List_W124_M119.pdf

You want to go to the "Diagnostic Module" pages to get the correct codes.

THROW AWAY any other so-called "code translation" document into the recycle bin, as it is completely useless. Use the attached/linked document ONLY.

 

[Kyiv]

I also noticed the ambient air temperature sensor is loose in the back of the driver's side headlamp housing.
It seems that it is missing something to hold it tight.

This is what you are missing. If the air charge temp sensor itself is bad it'll trigger CEL and a limp mode. Missing clip/bracket and sensor being lose does NOT trigger a CEL and limp mode (significantly reduced engine ouput)

 

[frall]

Error code 3 from the LH-modul (Pin 4 of X11/4) refers to the
ECT sensor (B11/2), sensor circuit 2.
That is not the air temperature sensor!

 

[tewfiks]

Already took care of the moisture check.
First thing that was done.
Thanks.

Part number on the clip?

 

[JC220]

Already took care of the moisture check.
First thing that was done.
Thanks.

Part number on the clip?

And insulators are new too? Both of them? Lots of owners caught out by that.

What spark plugs were installed and what gap?

(Trying to help by the way- not nit picking!)

 

[Kyiv]

Already took care of the moisture check.
First thing that was done.
Thanks.

Part number on the clip?

 

[Kyiv]

And insulators are new too? Both of them? Lots of owners caught out by that.

What spark plugs were installed and what gap?

(Trying to help by the way- not nit picking!)

I like your irksomeness towards uncouthly presented information

 

[gerryvz]

Insulators should be replaced at the same time that caps and rotors are replaced. If any one of those three pairs of parts is not replaced, when one pair is worn or not working correctly, then the entire ignition system is compromised, and at minimum suspect. Insulators MUST be replaced when caps and rotors are.

 

[a777fan]

And here are a couple of pics with the IAT sensor clip installed correctly. Courtesy of @Hakie !

 

[tewfiks]

Insulators should be replaced at the same time that caps and rotors are replaced. If any one of those three pairs of parts is not replaced, when one pair is worn or not working correctly, then the entire ignition system is compromised, and at minimum suspect. Insulators MUST be replaced when caps and rotors are.

Insulators?
Caps, rotors, dust shields, coils all replaced.

 

[gerryvz]

This is an insulator. I'm not aware of a dust shield in the ignition system. The insulator provides electrical isolation between the cap/rotor (which is actively transferring electrical sparks) and the cylinder head/camshaft area.

You should also check the resistance of your plug wires, to make sure they are conducting the electrical signals properly.

 

[tewfiks]

https://www.autohausaz.com/pn/1191580188

I assume this is the same as an insulator

 

[gsxr]

Dust cap / insulator... different names, same item. Should be a 1-time replacement.

On a problematic car, I'd consider replacing the seals on the camshaft sprocket as well - cheap insurance, but another hour or two labor.

 

[gerryvz]

Insulators should be replaced at the same time that caps and rotors are replaced. If any one of those three pairs of parts is not replaced, when one pair is worn or not working correctly, then the entire ignition system is compromised, and at minimum suspect. Insulators MUST be replaced when caps and rotors are.

Insulators?
Caps, rotors, dust shields, coils all replaced.

This is an insulator. I'm not aware of a dust shield in the ignition system. The insulator provides electrical isolation between the cap/rotor (which is actively transferring electrical sparks) and the cylinder head/camshaft area.

I assume this is the same as an insulator

Dust cap / insulator... different names, same item. Should be a 1-time replacement.

I just finished a long, un-interrupted read of @robm.UK's technical white paper on the cause and remedies for the common ignition mis-fires that are very frequently occurring with M119 engines using distributor-based ignitions (119.97x and 119.96x variants).

As I noted, and this passage from @robm.UK's white paper mentions, on page 70, the primary and pretty much SOLE purpose for these round caps is for the electrical isolation of charges inside the distributor cap from shorting to ground, which would be on the distributor recess on the end of the cylinder head cover.

Note the passage below, from Page 70 of @robm.UK's white paper, which expressly reiterates what I mentioned above in my quoted post:

 

[tewfiks]

I will order a new set of "insulators" and see if this help smooth the idling of the engine.

I did pull the code off of the LH module, it flashed 13 which leads to the IAT sensor (B17/7), open short circuit.
Now I need to determine what the IAT sensor is.

 

[tewfiks]

IAT sensor is the intake air temperature? I have already replaced this and am awaiting for the clip that holds it in place.

 

[gsxr]

If the IAT was ever unplugged with the ignition turned on, it will store that code. If the code keeps coming back with the sensor plugged in, then it may be faulty. All the IAT does is pull some ignition timing if it's REALLY hot outside.

 

[frall]

You can measure up the ressistance as shown in the attachment.