First off sorry for the wall of text, try to bear with me.

I picked up a cheap E420(Non ASR) ,145k miles, just to toy around with a couple months ago, cant find any 500E/E500s around here sadly.

I bought it knowing it had a few issues. Car had a couple cylinders misfiring. Fixed it by changing valve cover gaskets( which is now slowly leaking again at front driver side, wonder if i tightened it too much), changing plug wires to beru, ignition coils, and I also cleaned cap and rotors(replaced in late 2010 iirc, probably needs more).

This fixed my misfire, car ran much better after this, but it still runs rough. Im not sure where to go from there. The exhaust is leaking in the center, where i believe the resonator is and whoever tried fixing it did a terrible job(previous owner). I figured the cat was plugged but it gets real hot, probably need a new o2 sensor.

Other than that its been running decently, until today. It started this morning, idle rpm bounced down to 400ish for a split second a few times and went up to normal. Then The car goes into limp home mode, pedal does absolutely nothing, even if you floor it and shakes violently at idle, rpms go to 400ish. Limp home mode wont go away until i turn it off and sit for a second, then restart. It also fixes it self after some duration and LHM goes away. Its never done this before.

Last Saturday i replaced the LH module from a 92 400E at a local pull a part. Car responds better, especially at WOT. I am unsure if this would cause any issues of the sort but just putting it out there.

Later that day, i went to autozone picked up some vacuum tubing, due to seeing some dry rotted tubing at egr, ezl, etc. After replacing those i put my hand on the radiator and the neck broke in half. Dry rotted, looks like i have to order a new radiator. Which is better nowadays nissen or behr? Also seen a hella, i figured that would be good as well.

More issues i can think of at the top of my head...

I checked codes with a blink reader i built, got all codes on all the pin outs for the 38pin DTC and the self checking one. All codes i found from 2 months ago, i should have cleared them all beforehand but w/e


****************Codes [spoiler]Pin 4 LH-SFI (LH Sequential Fuel Injection)
4 - Voltage at hot wire MAF sensor (B2/2) insufficient or too high, or open circuit in
ground wire at hot wire MAF sensor

Pin 6 ABS (Anti-lock BrakeSystem) - For models without ASR
13 - Brake lamp switch (S9/1)
25 - Left front axle vehicle speed sensor (L6/1), implausible signal
26 - Right front axle vehicle speed sensor (L6/2), implausible signal

Pin 7 CC/ISC (Cruise Control / Idle Speed Control) - For models without ASR
2 - CC/ISC control module (N4/3) N4/3
23 6.0-8.0
Safety contact switch (M16/3s1)
23 17.0
Stop lamp switch (S9/1)
23 2.0
Cruise control switch (S40) OFF
CC/ISC control module (N4/3) N4/3
23 3.0, 5.0
Actual value potentiometer (M16/1r2)
23 11.0
Starter lock-out/back-up lamp switch (S16/3) (transmission range recognition)
23 14.0
Engine speed (TNA) signal
23 15.0, 16.0
Vehicle speed signal (VSS)
Safety relay within CC/ISC control module (N4/3) N4/3
CC/ISC control module (N4/3) N4/3
Engine harness Check harness wire insulation.

45 Fuel safety shut-off of electronic accelerator or cruise control active
2 EA/CC/ISC control module (N4/1) or Safety contact switch (M16/1s1) or Stop lamp
switch or Cruise control switch or Actual value potentiometer or Starter lock-out/back-up
lamp switch or engine speed signal or vehicle speed signal or closed throttle position
switch or safety relay in EA/CC/ISC control modu
11 - Fuel safety shut-off signal to LH-SFI control module (N3/1)
Closed throttle recognition signal to LH-SFI control module (N3/1

Pin 8 Base Module (Power supply for the other modules – has 4 fuses on top)
5 - Maximum allowable temperature in module box (F23) exceeded
6 - A/C electromagnetic clutch (A9k1) jammed or poly-V-belt broken
11 - Base module (N16/1) voltage supply output fuse F3, open circuit.
13 - Base module (N16/1) voltage supply output fuse F4, open circuit.[/spoiler]
************Codes

Some of these codes i have tinkered with, ie swapped fuses in BM. fixed maf, brake lamp switch. Remember all these codes are from when i got the car. Now today i tried checking codes again, but i get no power from the 38pin, what could be the issue? I get power from the pin 1 on the built in blink reader, but not the 38pin, makes it hard to hunt problems when that does not work.

Also, when i start the car, the SRS comes on for a few seconds and goes away, i dont think this is normal, my 94 e320 has never done this. The module box has a vacuum tube going into the car, i assume there is a fan supposed to be sucking the hot air out of the box but i hear nothing from it.

Another quirk is an annoying whine from the transmission when manually selecting first or second(less pronounced), reverse takes a second or two to engage as well. I reckon a trans oil change + filter would suffice?

Things i have changed
New
Bosch non resistor plugs
Beru ignition wires
Ignition coils(one bremi one bosch)
valve cover gaskets
timing change guides
most relays under fuse box
copper ceramic fuses
delphi 2010 upper wiring harness
92 400E LH module
fuel filter

Lower wiring harness has not been changed. Insulation crumbles. I believe its shot, the oil pressure gauge does nothing in the car.

If anyone has any insight on my issues, it would be greatly appreciated. Hope you made it through that wall of text

Sorry I did not go thru your posting completely, but knowing these cars, 2 things are foremost to be repaired:

1.- Upper wiring harness
2.- ETA wiring harness

All other issues are off until those 2 problem areas are addressed

__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

Upper wiring harness has been replaced. Have not touched ETA or lower harness. I plan to have a look at the ETA this weekend and rewire it if need be.