Problem: throttle not always responsive under engine load.
'88 260E

Hello,

In order to troubleshoot the intermittent problem of throttle not being responsive on my '88 260E, I meaured the EHA current while I was driving. I also hooked up a vacuum gauge to see vacuum use.

At engine operating temperature, key on , ignition off, I read +19 mA at EHA.

At idle speed, I get 0-4 mA . I think this meant that due to vacuum guage connections I was getting a bit of vacuum leak and the ECU was trying to correct it. The vacuum reading at idle was about 15 inHg. Is this normal?

As I started driving, the EHA current was moving between 0-8 mA. However, often, after a stop at any traffic light, or acceleration from a slow down, the throttle is not responsive. I the have to lift my foor off the pedal and depress even more to get the response I need.

I checked the readings of EHA and the Vacuum when I depressed the accelerator (but no immediate response). EHA current stays around 0-4 mA. The vacuum guage will go to zero, stays there for couple of seconds and then it goes to about 15 in-Hg or higher.

My understanding is that, under engine load, such as acceleration from a slow down or from a stop, or uphill, when the gas pedal is depressed, ECU, based on inputs sensors such as Air Flow Meter, O2 sensor etc, should increase the EHA current to 8-10 mA to cause more fuel flow to flow. I did see this increase in current at times when throttle response was OK. However, the current never reached +13 mA and the vacuum gauge always dropped to zero for a second or two whenever I depressed the gas pedal.

What would prevent the ECU from detecting the engine load? o2 sensor is new and I checked the Air Flow Meter for continuity. I also cleaned the throttle body and links. What else can I check?


Thanks.

__________________
Zorin

'88 Benz 420 SEL
'79 Porsche 911SC ('87 Carrera Engine)
'00 BMW 540 Sports Package
'99 Land Rover Discovery

86 300E - Manual (sold)
88 260E (sold)
84 944 (sold)