Hello all,

I have an '86 240DL sedan (M46 manual transmission) with 250k miles. Even though it drives generally well for a high-miles car, it has a weird problem that nobody seems to be able to fix. So I'm turning to you Brickboarders for opinions, ideas, or any clues for where to look next. (I'm not a mechanic at all, but I try stay as informed as I can). This may get a bit long, but I beg of you, bear with me if you can.

The problems:

1) (INTERMITTENT - happens about one in twenty times) After driving for a while at highway speeds, then starting up (from 1st gear) after stopping for a red light or stop sign (not turning ignition off, just going to stop and go driving after an hour or so of highway driving), sometimes the car just will not 'go' -- There is a whirring noise (sounds like the pumps are all working), but the engine acts as if it is not getting any gas. Sometimes pumping the gas will get it going again, but in worst cases I have to turn off ignition and crank it back up, almost like 'resetting' the car. Then the car drives away. Sounds electrical, right? Or maybe fuel system? Sometimes the car just hesitates really hard for a half-second, then 'catches' and takes off with a loud chirp of the rear wheels. Very sloppy. People stare at me as if I'm a menace to society or something...

2) I got caught in a snowstorm in western Pennsylvania on Tuesday. After driving at 65+ mph for four hours, I hit the bad weather. When I slowed down to cruise at about 45-50 mph, the car started to 'buck' -- as if the engine was getting fuel for a second, then the fuel system went dry for a half second, then gets fuel for a second, then goes dry, etc. I could not keep a steady 50 mph in either 3rd (3000 rpm) or 4th gear (2200rpm). If I sped up to 65mph (3000rpm in 4th), it would drive along steadily. I was very upset about this and decided to turn back. It seems that once I got back down to sea level, the car settled down and I could drive along at 55 to 65 mph without the bucking. However, it was still bucking and hard hesitating when I stopped at red lights, the whole way home.

3) After driving for a couple of hours at 70 mph in OD, even after going out of overdrive (depressing the OD switch on the shift knob to turn off the "5" dash lamp) the overdrive 'sticks' -- Even if I slow down to less than 50 mph or downshift to 3rd, it seems as if the overdrive is still engaged, i.e. I'll be trying to drive along at 40 mph in 3rd gear, but the revs will be *way* lower than normal, like 1200 rpm. If I come to a complete stop and start up again from 1st gear, usually the OD will finally disengage.

At no time did the car overheat or appear to be losing oil pressure. The engine does not leak or burn oil, or leak radiator fluid.

4) If I do a little 'back road barnstorming' (high revs in low gear around curvey country roads), the car will do its bucking 'hesitate, choke and start off with a screech' dance every once in a while. It's almost as if the stress of higher rpm's (3500 and up) causes the car to freak out.

---

Here is what has been replaced or serviced in the car, in efforts to fix this problem, as well as some other problems.

1) New engine wiring harness installed.

2) New alternator and battery installed.

3) New distributor cap and ignition wires installed.

4) OD ATF drained and refilled with new.

5) OD switch (both the switch on gearshift and the switch on transmission) and solenoid replaced (in-dash relay seems OK).

6) Air filter replaced.

7) Injectors checked, one replaced with rebuilt part.

8) In-tank fuel pre-pump replaced. (This was just done on Wednesday, and did help general driveability -- but did not cure the intermittent hesitation problem).

9) New ECU (supposedly) installed when I purchased the car a year ago.

I've been told that the air mass meter is working fine, and it "just isn't likely to be causing the problem".

I've also been told that the vacuum level in the air and fuel systems seems fine.

I've also been told that the compression reads good in all cylinders, appropriate for a car with a lot of miles, but they all match up pretty well. So there's apparently not a situation where there is one strong cylinder and three weaker ones or anything like that.

I will be replacing the fuel filter, which looks like it may never have been replaced. Could this cause a problem like this? Of course, one mechanic told me this could definitely be the problem, while another one told me 'no way could it be the problem'. Argh.

So please, give me any ideas at all, so I can try to trace down this bizarre problem. I bought the car for $3000 about a year ago and have put another $3500 into it, and I still can't seem to get rid of this incredibly annoying (and possibly dangerous) problem. I've told this story to several mechanics, but they don't seem to believe that I'm telling them what's actually happening.

Thanks to all for your time reading this and any suggestions you may have.