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Duratec misfire

Posted by uncledave_ct (My Page) on
Wed, May 30, 07 at 9:57

I have an '02 Sable wagon, 78k with the 3.0L Duratec. One morning last week, when accelerating onto the highway, the engine suddenly lost power and the engine light began to flash. After approximately 30 seconds, full power returned and the light stopped flashing and remained off. I did not attempt to recreate the problem because I needed to get to work. :p)

Based on research, this indicates a misfire, although I will have it scanned to confirm the code and determine the affected cylinder(s). If anyone has extensive experience with these cars, what would be the most common cause of intermittent misfire on heavy acceleration? FWIW I can perform any work that does not require engine disassembly, but I know my limits. Thanks!

Follow-Up Postings:

RE: Duratec misfire

If the plugs and plug ignition leads have not been changed in the last 30,000 miles, check these. The spark plug and coil leads may have gone high in resistance. Check you repair manual for proper resistance. In the absence of data, assume that the resistance should be in the range of 5000 to 8000 ohms per ft of lead.

For old spark plugs leads, the resistance may be low enough to give reliable cold starts, but greatly increases resistance when the leads get hot. Marginal spark delivery will show on heavy acceleration becasue the voltage to jump the gap goes up with the amount of charge in the cylinder (gas pressure).

RE: Duratec misfire

The plugs and leads are original so I'll start with these. Someone else also mentioned to replace the fuel filter and/or check fuel pressure. Thanks!

RE: Duratec misfire

Yep, that's where to start.

RE: Duratec misfire

If the engine lost power for a full 30 seconds, I wouldn't suspect plugs and wires, sounds more like fuel system to me. When I have ignition misfires, they only hit for an instant or two, then gone. Also, misfires are more prone at lower RPM and under load because this combo requires more voltage to fire the plugs.

RE: Duratec misfire

I did scan for stored or pending codes, but there was nothing, it's clean. Perhaps it was not ignition-related after all. I think I'll bring it somewhere to check for fuel system issues. I'll replace the fuel filter regardless, since it's unknown whether it has ever been done. Thanks everyone!

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