[luschka]

I've had an ASR limp mode for a while, and I replaced the electronic throttle assembly (ETA) from a known good car that was fully serviced for the eco wiring harness.

After replacing, initially I was out of the ASR limp mode, but under acceleration, the throttle hunts as if it has a massive vacuum leak. The car can be driven with the hunting/surging throttle but only at about 5mph.

I re-checked all of the vacuum connections I made (new MAF to TB coupler with clamps), new crankcase vent hose (part closest to the TB; other 2 sections not yet installed - existing hoses in apparently serviceable condition). I checked for vac leaks by spraying with starter fluid. Nothing obvious.

After re-installing the ETA to double check vacuum lines, ASR AND ABS lights are now on again.

Blinker code reader blinks 30 on pin 6 - indicates "CAN data bus to EA/CC/ISC control module (N4/1) interrupted"
I have previously had this error but it went away after re-seating the EA/CC/ISC (EGAS) module.
STAR diagnostic computer is in the mail from china, ordered several weeks ago.

I have checked all vacuum hoses, tried to detect a vacuum leak by spraying starter fluid around suspect parts, and checked all the pins on all the electrical connectors. The return spring for the throttle linkage is properly installed. I adjusted the throttle cable linkage per attached WIS manual so that there is just enough tension to take the new ETA to WOT position.

I think either:
EGAS module is bad (I believe this car had a bad ETA, which can short and damage the EGAS module)

I believe I have a good EGAS module from my parts car, but I don't want to swap it in and destroy it if the ETA is bad (below)​

"Known good" ETA could have still had eco wires? Which broke after all the manhandling when I swapped and removed/reinstalled to re-check all vacuum lines
Discrepancy with length adjustment on the throttle linkage?
Some sort of WOT calibration procedure which I don't understand? codes making me crazy!!

The above seems to just say to push the gas pedal down to the kickdown switch with the engine off, key in the on position - I did, it doesn't seem to do anything.​

​

If anybody has any advice or had a similar issue, let me know. It really seems like a vacuum leak; I simply just can't see anything I could have damaged.

 

[luschka]

Updated, apparently solved s/p 12 mile test drive (EDIT: ASR light came back on after 25 miles, but the car is driveable). Not only is the car drivable again, but the ASR light/limp mode is GONE!!!:

I really needed a working car again, so I swapped the original-to-the-car ETA assembly back on. Fired it up and, wow, the ASR light was out. The ONLY net change after this whole ordeal (aside from replacing some hardened rubber parts) was that I calibrated the mechanical throttle linkage per the above attachment, when closed and at WOT (but before activating the kickdown switch at the gas pedal).

The mechanical throttle lever arm at the ETA needs to rest on a stop when the throttle is closed, and rest on another stop at the other end of its travel when at WOT. My mechanical throttle was too "loose": pulling the ETA open but not far enough at WOT; it was only going about halfway to the WOT stop as seen on the ETA's lever arm.

This car has been serviced by some backwoods mechanics; unlike my previous W140 that was dealer-only serviced for anything important. I think someone clueless had adjusted the plastic adjustment nut controlling the throttle cable tension (easily accessible back between the air box and the firewall), and this brought the mechanical throttle out of sync from the electronic throttle.

So, just pull the airbox and check the tension on your throttle cable/linkage if you buy a car and it has an existing ASR limp mode.

PS: Still a complete mystery to me why the known good ETA from my parts car would cause horrible vacuum leak type symptoms. I will have to double check the part numbers, but the two cars are both ASR equipped, 1994 model year cars. Maybe there is some sort of "learning" procedure involved with the ETA units? In most forum threads, people send out their existing units for rebuild, I haven't read anything about anyone swapping one ETA for another from ebay/a different car.

 

[luschka]

Solved: The "Known good" ETA I swapped in, with these weird fluctuating throttle symptoms, was in fact affected with soybean biodegradeable wire disease. Somehow, in the previous car it worked flawlessly until it was removed. It has been sent out for repair.

 

[luschka]

The ETA suffering this fluctuating throttle was found to have a bad clutch per Don Roden at RFC electronics who rebuilt it.

It did not occur to me at the time of installation, but I imagine if the ETA was simply unplugged, the fluctuating throttle would likely disappear, as the ETA would then act as a purely mechanical throttle plate. Worth trying if an ETA related problem like this happens when you're out and you need to limp home.