Suspect ETA?

[Dan O.]

Hi all, I'm starting a new thread as a follow-up to one that died out back in November (E420 fails smog miserably). Still haven't passed smog but I've been busy with the holidays, etc and just got back to working on the car. In the interim I replaced a badly needed flex joint and a throttle cable; shortly afterwards I started seeing some odd behavior that could be related to my smog problem.

On start up the car is now exhibiting an unstable idle that eventually levels out around 750 rpm, the previously working cruise control is now inoperative. Turning on the a/c brings the idle speed down to 500 rpm. Pulled codes today and I got 2 from pin 7 and 6 from pin 19. I had a hard time clearing the 2 from pin 7 so I tried clearing and re-checking w/o cycling the ignition and that seemed to work, that is until I re-checked after the ignition was cycled; it would appear code 2 is resetting immediately after the ignition is switched on.

Per the bit of research I've done this looks like it could be an ETA issue. The upper harness is a replacement Delphi part and looks to be fine, I don't want to touch the ETA harness because I'm sure it's original to the car ('94, non-ASR). Does it sound like I'm close?

 

[gsxr]

I am not sure if non-ASR cars have the same issue with the ETA, since the ETA (and control module) is completely different. However, it is a good possibility. Check the date codes (see the forum Wiki) and if your ETA is original, I'd start looking for a used one with a late date code as a replacement...

 

[gerryvz]

Idle problems can be the result of a vacuum leak, and the erratic behavior can be caused by the computers trying to compensate for poor conditions.

Before assuming it's the ETA, I'd do some basic diagnostics and get a smoke test done to ensure you don't have any vacuum leaks. Often times, it's the most simple/cheapest things that cause the problems, not expensive items.

 

[emerydc8]

My guess is that you disturbed the ETA cable when you were working on the throttle cable and the cable itself is toast. I had this happen on my old non-ASR 93 400E. The idle problem would happen along with the inop cruise control. I accidentally discovered it was the ETA cable that was bad as I was leaning on the air box, which moved the ETA cable. Without the engine running, but the key on, I heard the ETA motor move when I pushed down on the air box. You might want to try carefully repositioning the ETA cable to see if there is any effect on the engine idle or cruise control. I was able to get mine to work again for several years and never messed with the ETA cable again.

This is assuming the problem is not what Gerry pointed out in the prior post.

Also, check the Delco fuses on the control module.

 

[Dan O.]

I've given the engine compartment a few cursory glances for vacuum leaks but I'm all for doing a smoke test in order to put any remaining doubts to rest. I'm the last one that wants to blame the ETA harness but the dead cruise control, the lack of a/c idle up and the likelihood that the ETA has never been touched is leading me down that path. I'd really like to get my hands on a used one and tear into it, from what I've read they can in most cases be repaired for far less than $1500 worth of effort. I did stop by the self-serve yard and just missed my chance as there was an E420 with a freshly stripped engine, I managed to pick up the LH module that was left on the passenger seat though.

Also, with key on/engine off should the ETA be making noise? The ETA on my other E420 (ASR-equipped) does make a clearly audible noise under the mentioned conditions but no such noise from the non-ASR car.

 

[emerydc8]

The non-ASR ETA should also make noise.

As for rebuilding a used ETA, unless you are really good at soldering electronic components, and you have the spare reference potentiometers that usually fail (I think the original vendor no longer exists), it is better to find a late model ETA on ebay. Go to the wiki page and read all about the date tags. I think they stopped using the bad insulation after 1996, so any used ETA that you get prior to that time is probably equally as bad as yours. If you vertically slice a small section of your ETA cable, you will probably see that the insulation is toast.

Out of curiosity, when you replaced the throttle cable, did you adjust it correctly? The Idle Speed Control function of the ETA is supposed to regulate the idle speed -- not the throttle cable.

You might want to turn the key on and move the ETA cable around slightly to see if you can get the ETA motor to run.

 

[Christian_K]

That is corret.
The non ASR ETAs also make noises and if its dont, something is broken. At my Friends E320 it was the fuses that were corroded and a broken over-voltage regulator thingy (that at the V8 cars is embedded in the Basemodule (GM)).
You have to notice here that the electrical Part of the non-ASR ETA is only used for idle speed and cruise control. Everything else is still drive-by-cable/wire-rope/bowdencable
So there is no limp mode with the pedal, that only in the last 1/3 it will go forward.

 

[Dan O.]

Jon D. had asked earlier if I adjusted the throttle cable correctly, truth is I don't know and I'd like to go through the procedure again to rule out any weirdness in that department. I attempted to figure out the adjustment procedure by referring to this:

http://www.w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Engine/119/30-1010EB.pdf

The wording for step 7 is throwing me for a loop, this sounds like a two man job requiring one guy to hold the accelerator pedal down to the point where it contacts the kickdown switch (but doesn't actuate it) while the other guy verifies that the throttle bell crank has made contact with the WOT stop on the ETA (and adjust bowden cable nut if necessary). Unless I'm reading this incorrectly it sounds like the cable should be adjusted so that the bell crank will run against the WOT stop before the pedal can actuate the kickdown switch, how then does the kickdown switch ever get actuated when you "floor" the pedal? Is this where the spring at the end of the bowden cable comes into play, allowing just enough cable "stretch" to operate the kickdown switch? Since I didn't fully comprehend step 7 I simply adjusted the cable so that everything was in the same position as it was with the old one, so yeah, the adjustment is probably off from where it should be. Is something getting lost in translation or am I not understanding correctly?