Still working on this 280SE coup. I have fixed the injection thermostat problem. The car should not be running rich. I have re-set the points and timed (I'm running it now at TDC give or take 2 degrees). At 3500 rpms + when acceleration (passing) in the 65 to 80 mph range the car seems to miss or fires in the exhaust. Has hesitations and chokes a bit. when you let off the gas just a hair this stops. Low speed acceleration does not have the same result, seems fine. I was thinking the vacuum advance wasn't working right. Does anyone have any suggestions on what to check?

Michael

The basics - plugs and plug wires?

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Bad coil?

Too lean? [duck]

:p

__________________
Johan Limcangco
Manila, Philippines
79 350SE (W116)
86 230E (W124)
http://www.geocities.com/johan01.geo

Check your vacuum lines . If the cheap fix doesn't make itself apparent, bite the bullet and pay for a diagnostic, it will pay for itself in the peace of mind and point you in the right direction. Unless you are like myself and enjoy the challenge of a problem driving you to edge of raving lunacy while viewing a professional opinion as cheating.

Very Funny reply!! I often feel the same way. Somehow it is cheating to give in and take it to a shop.

The car has new plugs and wires, mouths old. however all this was done before I owned the car. I don't know about the coil. The car fires on all 6 through out the range except when pushed into the 4000 rpm range. I have a spare vac advance, and some lines, I'll check that. Could there be a problem with the point ?

In terms of "too lean" the car was running way too rich, the injection thermostat was stuck. I freed it but now I think it is stuck in the hot postion. But that should be a problem at highway speeds.


Thanks,
Mike

You want to time these at 30 degrees @ 3500rpm.
The vac on these mech FIs is retard, not advance.

Re-timed at 3500 rpm, at 30 degrees. I really thought you could time this year at idle. Still it makes better sense to time at speed. Also, the injection t-stat was still not opening fully so it was running just a little rich, just enough to screw things up. I think I have finally fixed that. It work now with out getting stuck, what a pain that was.

No miss now at any speed, will see how the fuel economy is.


Mike

These seem to run best when , after the 30 degree-3500 rpm timing is set, you then get the idle around TDC.
This can be accomplished without moving the dist setting by shortening the rod adjustment to the vac retard .
The retard is at its highest at idle because the air plate is fully closed. As soon as the throttle opens, the advance comes right up.
The called for specs of ATDC were early emmision control, but they run much better closer to tdc than retarded......
Again, the main thing is 30 and work back without changing that.

Art,

Your just about 1 step ahead of me. 30 degrees at 3500 rpm I did. Runs now at 10 BTDC at idle and about 950-1000 RPM. If try to get the rpm's down; closer to TDC, That is when I have the miss at speed. Suggestions....

Mike

The readings you have [ both rpm and damper] are what is seen w/vac.
retard dis-connected. That indicates that the vac retard is not working.
When working correctly. the retard should
bring it closer to TDC and the idle lower [ approx700-750]
There should be a change when you disconnect the vac hose to the dist vac servo.
Check for vac at the line and then pull vac on the servo while checking w/timing light/
I am assuming your dist has the single vac. line?

get back to me on it and include the dist #. Then I can give you exact specs.

PS the point I was making in the orig post is that after you get the 30 degree timing set, do NOT turn the dist any more for the idle settings. If you do, you loose the 30.....

There is no change when the vac is disconnected. So the vac diaphragm has a leak in it or the line does. It is a single line vac and I have a good spare. So that sounds like it.

Mike

Or the rod in the dist that connects the vac dia. to the advance plate is broke/off/binding.
The easy test is to take the cap off and see if the plate moves when applying vac at the hose port [ with hand pump]

Once all is well, remember to set the dwell/gap BEFORE timing
the dist/eng., as the gap effects the timing degrees......

Ok... Still at it.

Art, I checked the vac advance, yes it was stuck but I got it to free up. BUT, there is very little draw from the intake. I took the intake ( front section) off and cleaned it out, re-installed. Still has very little suction. Since this car is a coup it has a second vac port on the back side for the seat locks. I checked that, it had plenty of suction. I then connected the vacuum advance to that port. The whole thing worked fine. So in the end I still don't know how to fix this problem.

Mike

The vac port for the retard is at it's greatest when the throttle plate for the air is closed . [ at idle]. The reason for this is to have retarded spark on deceleration/ idle. As soon as the plate is cracked open, the vac drops and the spark advances. [ vac retard vs. vac advance- these dist have NO vac advance, only mechanical advance.]
So if there is little or no vac at the port and the port is clean, it is possible the the adjustment for closed throttle is not set to spec. This is usually noticed along with high idle rpm.
The best vac you will get at idle is with the plate just closed and the air bleed screw set with the help of a vac gauge.
You may want to take note that many of the owners of these who have stick shift actually do away with the retard and set them up at about 2 degrees BTDC with a higher than spec idle
[ approx 850/900 . 113 guys like this as they are looking for as much performance as they can get [ which ain't much}].
Try the gauge tweaking and see what you get