1988 240DL will go into a retarded timing type of power loss. It will do this whether the gas tank is full or empty. Mostly when the humidity is high, although not always. I think I can hear an electrical relay type of click when it derates, and again when it returns to normal. One fitful time the car would accelerate from stopped to 10 MPH normally, then just switch to no power. Pressing the gas pedal did nothing for increased speed, just got the low "waaah" sound like a carburated car starving for fuel. It did this repeatedly, 5-6 trials, then when I shut the engine off and restarted right away the car ran okay again. I've changed all the fuses, O2 sensor, fuel relay, under body fuel pump, distributor cap, rotor and set timing. Once the car is up to steady speed it runs reasonably well, but will not accelerate like it used to and takes a very long time to wind up RPM's. Air Mass Meter is original as is wiring and Catalytic Converter. Air filter has been changed recently. I'm ready to take it to a repair shop but like to be armed with some information from people who may know what this condition stems from.

Your comment about it possibly being related to humidity should get you thinking along the lines of some triggering event or condition -- similar to heat causing electrical problems in a faulty component or circuit.

So, check the wiring harness for rot. When my '86 harness failed, the engine died wheile the blower fan speeded up to High.

Do the multimeter diagnostic checks of the pin connections where the harness fastenes to the FI/ECU inside the car. Maybe you have a burned spot on the circuit board chich is responding to environmental contitions, while not being totally failed yet.

Lastly, could be the pin connection sleeves at the ignition ICU (right fender) have some corrosion, or were loosened by a previous owner/technician if this mudole was ever disconnected. (Bentley manual says don't disconnect this harness, or you need to replace the ICU dur to breaking the pin connector sleeves. I have heard of someone saying they have replaced those sleeves.)

My '83 245 did the same thing 8 months ago. It was only an occasional occurance, but an annoyance nonetheless. Hard wire your main and fuel pump relays to a manual switch, see if car runs. Mine's been rigged up like that since I decided to stop looking for the culprit, and it has worked fine ever since. Just don't forget to turn off the switch at night, if the ecu is drawing current too long, it'll eat your battery for a late night snack. An added bonus of this setup is that if you make the switch look inconspicuous enough, its a brilliant anti-theft measure. If you turn off the switch when you get out of the car, any theif will just think the car they're trying to steal is a piece of crap that won't start. All I can say if you don't feel the need to do this is, don't worry, your car will probably just fix itself. I know mine does sometimes.

I had to replace my cat. converter about 1-1/2 years ago. It started to break up on the inside and caused power restrictions especially noticible uphill. I wouldn't be surprised at all if this is your problem as it is kind of an overlooked item. I picked up an exact fit lifetime part for $160.00 installed. It has run sweet ever since.

Good luck,

Jack W.

Is your exhaust system restricted? Remove the rear muffler as a test.

Cheers,

Richard,

When the air mass meter took a dump on my '84 242 back in '92 at about 86K miles, I was sitting at a traffic light. The car had been running fine all day. When the light turned green, the car accelerated normally up to about 15mph and then very abruptly lost power. It surged up and down all the way home, took me about 30 minutes to make the 4 miles back to my driveway. I poked around under the hood for awhile, couldn't figure out what in the hell was going on, and finally broke down and called the dealer. They had me disconnect the AMM (with the ignition OFF) and then start the car. I took it out for a drive around the neighborhood, no more surging, but it really wasn't driveable as it wouldn't revv higher than about 2500rpm. Volvo calls this "limp home mode."

Try this, and let us know what happens.

But remember to turn the ignition OFF before disconnecting your air mass meter, or you will definitely be shopping for a new one!