engine puffing black smoke

[uestvega]

81 Fiat Spider, 50,000 miles. Recently did full tune up including O2 sensor, plugs, distributor, fuel filter, air filter. The car ran great for a while but then this problem with the car starting to run very ruff and blowing black smoke out the tail pipe came bace. I assume it is running too rich or something like that. It is totally original, but this problem started 2000 miles ago, and it seems to be somewhat intermittent.

This is the first real issue with the car, it sputters and runs really poorly when this happens.

Any thoughts?

[narfire]

Has the black intake come loose or developed a hole?

[uestvega]

I replaced that as well a few years back as the old one was dried and cracked, so I don’t think there is an air leak from that new unit.

[narfire]

OK got that covered...... How about the timing? Do you have a timing light and check to see if the dist has moved any?
Should be 10 deg btdc. Perhaps the dist nut has come loose a bit and the dist has moved a tad or two.
Chris

[uestvega]

Hey Chris, thanks for the input.

The timing is all good. I am wondering if one of the sensors that control the fuel injection is faulty. Living in Toronto Canada, the car is garaged most of the winter, and I remember that last summer, I unplugged all the harnesses from all the sensors in the engine bay and cleaned the contacts and then sprayed them with an electrical contact cleaner lubricant and the car seemed to run better or like new after that, but the problem has come back.

Thoughts?

[narfire]

All the injectors working? have you, when at idle, pulled the injector conectors to see if there is any difference in the engine? Same with the plug leads? The grounds to the injectors are good.? (the two wires connected to the intake plenum.) I have had a broken plug and engine ran rough. Didn't notice it until I lifted the hood when it was dark out and noticed it arcing to the head. Another issue I have had was a plug lead rubbed enough on the underside of the hood for it to arc. Make sure they are tied down eh.
Toronto...garaged most of the winter... huh? Watching the news, you guys have been playing golf in shorts the last couple of months Still top up here and cool, record snow at the ski hills this year.
Chris

[majicwrench]

Black smoke = too rich. Air leak causes too lean, so that not an issue. Timing won't do it. Coolant sensor or conneciton very possible, if ECU thinks engine cold will enrichen mixture. Injector sticking open also a possiblitly. Here in shop I would test coolant sensor with lab scope as engine warmed. Replacement of sensor and connector might be the thing to do in a backyard situation, not very expensive.
Keith

[rryhol]

It is better for you to got a Fiat ECU Scan,check you cpu and engin to see if there are big problem.