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Going over last weeks sudden stall out and the trouble shooting afterwards has raised a question about the AMM limp home mode test.
Inga my faithful 1986 245DL 221K, suddenly died on the way to work when rolling along with the flow of traffic on the Beltway (2800 rpm) last week and would not restart. Got the hook and was able to get her started by jumping the fuel pumps or so I thought. Chased the fuel pump bunny without success, she would start up but the issue now was that the idle would suddenly surge up and down and then die if you let her sit there in the driveway and idle for a few minutes. I was thinking it was the main fuel pump, but at the suggestion of the BB tried the Limp Home test on the AMM. She would not run at all, the engine would start, sputter, and then die. The fix was one of two things, I reset the AMM connector quite firmly. Then noticed that the connections on the coil were very tarnished and covered in oil. The oil was synthetic and from a dipstick pop up a month ago. The owner did not make sure he pushed it far enough. The flame trap is new, the rattle test on the oil cap passed,changed the oring after the incident, no repeats. Back to the story, after a good cleaning of the contacts on the coil, replacing the coil to dist wire, and the AMM replug Inga is running and idling like my piston slappin kitten should.
But.... If you disconnect the AMM Plug with the key out and start the car the Limp Home mode is still very rough. Gas Mileage is 24 to 26 MPH depending on the weight of the drivers foot. She has smoothly made the 84 mile round trip to work with no problems for a week now in bumper to bumper and running with the hounds. One thing I have noticed is that the the spark on the coil is orange, not blue. But that spark has been orange since I was given Inga seven years ago. This is the first time that I ever tried the limp home mode test by the way when everything was working.
The AMM is the 07 model just like the book says and it was cleaned with the CRC AMM Cleaner 3 months back. The air box has the thermostat removed and that hole at the bottom plugged. The air filter is 3 months old. The hose from the AMM to the throttle body appears to be good shape new within the last year. New plugs and wires installed 2 months ago.
So my questions are:
Can a coil getting weak cause the Limp Home mode test not to work?
Is there something else I should be looking at if the Limp Home mode test makes her run rough?
Is the owner just being paranoid and should leave well enough alone?
Any tips and advice on what to look at and test, as always is greatly appreciated.
Regards,
PT
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