Flashing check engine light?

[TexEx]

I have been trying to figure out why my truck is misfiring. First i replaced about 4 CoPs, 2 spark plugs then finally 2 more CoPs. seemed to run fine then engine light even went off after a bit of driving. today it started running back to crappy, vibrating at around 1500-1800rpms & running rough at a traffic stop with foot on the brake & in drive. In addition, the engine light began flashing when moving at a higher speed. I've own 3 different expeditions & this one for 3 years & have never seen a check engine light flash. Does anyone have an Idea what may be happening?)

 

[99WhiteC5Coupe]

A flashing check-engine light indicates a severe misfire, which can quickly damage the engine and/or the catalytic converters (due to unturned fuel).

Don’t drive it with the light flashing. Have the vehicle scanned for any stored trouble codes - which will point you in the right direction.

 

[ManUpOrShutUp]

I had similar issues when one of my fuel injector wires burned up near the connector. The issue was intermittent as the wires moved and the connection cut in and out. That's just one of many possible scenarios though. Without knowing the trouble code(s), all anyone can really offer are random guesses.

 

[TobyU]

The scan tool (really cheap on ebay) will tell you which cyls are misfiring.
Start there. The coil connectors like to break the locking tab and slide off.

Then start looking for chewed wires.

 

[TexEx]

Thanks, all good leads, really concerned about driving it & possibly causing further damage to catalytic converter as I have noticed a different odor in the morning from the exhaust while warm up idle..just to add this all started with just a slight rough idle & a non blinking CEL on. CODE WAS giving# 8 cyl. so I change the plug with a sp-546 motorcraft since i was way back there & was putting in the new CoP. I may have damaged a wire, just dono.

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[TexEx]

The scan tool (really cheap on ebay) will tell you which cyls are misfiring.
Start there. The coil connectors like to break the locking tab and slide off.

Then start looking for chewed wires.

Thx what is the brand of scanner, if you recall?

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[John Stephan]

If you've been dealing with the slight misfire for a while, you could have a vacuum leak somewhere. Extra air entering the system that is not monitored is viewed as excess oxygen in the system and the ecu will compensate by adjusting fuel trims. Fuel trims in these trucks are key to understanding run issues. If you have an Android device, I highly recommend the Torque app. It's a one time $5 purchase. Then get a cheap $15 ELM OBD2 Bluetooth device off Amazon. It's been invaluable to me in figuring out my 5.4L both 2V and 3V.

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[TobyU]

Even one cyl misfiring will give you a flashing light.
#8 might be only prob.
You didn't accidentally drop #8 plug going in or lean the extension sideways too much to where it could have put pressure on the insulator and cracked it did you?...been there.
Check the wires first.
Then lift up the COP and put an old plug into it and start it up and see if it fires nice and hard and each time it should regularly with no skipping.

If so pull the plug and inspect or put another one in. They are cheap.

If not ignition and a solid miss on cyl it is time to do compression test and pull valve cover.

 

[TexEx]

Tried cleaning & securing connections to cops & injectors then revved up the engine idle until it started flashing again & the engine just really dropped on power & idle, something is badly wrong..I will definitely figure out a diagnosis plan tomorrow.

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[John Stephan]

Check the MAF. Make sure there are no bugs on it or its swelling from corrosion.

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