560SEL Bogging AT Wide Open Throttle - PeachParts Mercedes-Benz Forum

Frank Reiner · #1 03-13-2016, 12:12 PM

Quote:

Originally Posted by davestx

I have not checked the compression but the spark plugs, wires, cap and rotor are fairly new. will pull a few plugs and see what they look like. The coil is older. The ECU is from a 560. To reiterate, the car has never run smoother since I changed the ICU the other day. Everything is perfect until I try to accelerate hard in the upper RPMs. It will get to the redline but just much slower than it used to and with an occasional buck. I read in another post that throttle linkage is sometimes the culprit. I will check that tomorrow or Monday. I will also check the air filter. It has been a while since I changed it.

I changed a number of things in the last few months trying to get the idle straightened out.
1. injectors ( it just occured to me that I did not change the seals because I did not have new ones handy. Could that be it?)
2. EHA. I damaged the one that was in the car but had a spare (untested) . can the EHA cause this symptom?
3. ICU. Can the new ICU somehow be causing this problem?
4. Fuel filter
5. Accumulator

Where does the signal from the throttle switch go? Could the signal not be making it to its destination?

Could something with the timing advance cause this?

The WOT signal is used by the ECU to a) ignore the O2 sensor value, and b) to provide a fixed-map mixture signal to the EHA. In addition, the WOT signal is used by the ignition controller (EZL) to slightly retard the timing.

What type(s) of spark plug wires, and plugs are installed?

davestx · #2 03-13-2016, 01:09 PM

Quote:

Originally Posted by Frank Reiner

The WOT signal is used by the ECU to a) ignore the O2 sensor value, and b) to provide a fixed-map mixture signal to the EHA. In addition, the WOT signal is used by the ignition controller (EZL) to slightly retard the timing.

What type(s) of spark plug wires, and plugs are installed?

Thanks for the explanation. That helps me rule out the O2 sensor.

The EHA is suspect to me because that is the newest part that was swapped in (prior to the ICU) and it was used. Is it possible that the EHA is the culprit or that is set too lean?

Regarding the spark plugs and wires, It is raining but I am 99% sure that the spark plugs are NGK BP5ES (they could be BP6ES). The wires are the correct Bosch resistor wires. I can get the numbers of the wires later today.

Frank Reiner · #3 03-13-2016, 06:34 PM

Quote:

Originally Posted by davestx

Thanks for the explanation. That helps me rule out the O2 sensor.

The EHA is suspect to me because that is the newest part that was swapped in (prior to the ICU) and it was used. Is it possible that the EHA is the culprit or that is set too lean?

Regarding the spark plugs and wires, It is raining but I am 99% sure that the spark plugs are NGK BP5ES (they could be BP6ES). The wires are the correct Bosch resistor wires. I can get the numbers of the wires later today.

If by "resistor wires" you mean copper conductor w/resistor cartridge at the spark plug connection, then that is correct. If RFI suppression, non-metallic conductor type, not so good; total resistance is likely to be too high.

There is an off chance that the fuel pump relay is the culprit. Since it serves as the rev-limiter, it could be triggering early, OR, mechanical vibration of one of the internal contactors, in sympathy with engine vibration could be interrupting the pump circuit.

davestx · #4 03-20-2016, 09:11 PM

I found the problem today. One of the power wires to one of the fuel pumps had broken. It was hard to see because it was the one furthest in the shroud and the furthest wire in. I discovered it by disconnecting one of the wires from the pump that was visible. With the wire disconnected, the car would not start.

Thanks for all the responses.