Flashing MIL

Hi All,

Would like to know what your opinions are about a flashing MIL. How unsafe is it to drive the car? My understanding is that you may or may not be dumping fuel into the cat.
Let me tell you the whole story. The MIL started to blink on Friday on my wifes car, 97 sable 3.0L and she drove it home about four miles. I found three DTC's, 1 was the Cam sensor the other two were misfires on 5&6. Makes sense. Put in a new sensor on Sunday and test drove. Started flashing about four minutes into the drive when pulling out on the highway. Went home and pulled misfires on 5&6 but no CMP sensor fail.
So I checked to make sure 5&6 were fireing and they were. Am I doing damage by running this vehicle? What determines a misfire? Thanks for your help.

Hi All - Heres some more info. Sorry its a little long.
Compression on 4,5,6 was 120 steady, 129 steady and 132 steady. No evidence of a head gasket failure.
The resistance between cylinders on the coil pack was, between 5-1 11.12 ohms, between 6-2 11.16 ohms, between 4-3 11.15 ohms.
No arching seemed to be present on the wires.
Ran propane around intake gasket, best I could, and anywhere I thought there could be a vacuum leak, no difference in idle speed.
Plugs seemed a little worn, regapped - wires look ok.

Freeze data from when I went on the highway Friday: Code P0305 & P0306
RPM 2051, calc load 73.3%, coolant temp 162f, LT FTRM1 3.9%, ST FTRM1 7.8%, LT FTRM2 3.1%, ST FTRM2 4.7%, Speed 45mph, Fuel SYS CLSD.

Put it in the shop and just let it idle a bit and warm up, no MIL. Rev'd it a few times and the MIL started blinking. Turn ignition off and on and had a stedy MIL with misfire codes.

Reset the codes. Coolant temp was about 145f and I let it idle (about high 900s rpm) till full warm up to 198f. This took a good ten minutes and didn't touch the accelerator. MIL didn't go on as it did before within a couple of minutes. Seemed to be happy idleing. The live data at this point was:
MIL off, ABSLT TPS 16.9 - 17.3% fluctuating, RPM 887-942 Fluctuating, Calc Load 22.4 - 22.7% Fluctuating, coolant 198f, IAT 46f, Ign Adv 23-27 fluctuating, Second Air ATMOS, LT FTRM1 2.3 - 3.9% Slow Fluctuation, ST FTRM1 -3.1 - 2.3% Fluctuating, LT FTRM 2 4.7 - 7.0% slow Fluctuation, ST FTRM2 -4.7 - 4.7% fluctuating, speed 0, Fuel SYS clsd, o2s11 .1 - .7 Fluctuating, ST FTRM11 -1.6 - 2.3% Fluctuating, o2s12 .09 -.77 fluctuating, o2s21 .05 - .80 fluctuating, ST FTRM21 -2.3 - 2.3 Fluctuating.

All was good then rev'd 2k - 2.5k about 6 slow times and MIL started to Blink. Code where P0300 radom misfire and P0305 pending. Freeze data showed P0305, rpm 892, calc load 25.5, coolant 196, LT FTRM1 3.9, ST FTRM1 0.0, LT FTRM2 7.0, ST FTRM2 -1.6, Speed 0

Stop engine and restart, MIL goes solid. Does anyone see anything I might have missed? Nothing jumps out at me in the data above. Thanks for anyones help.

Is there any other light turning on/off on your dash? like, battery light, check engine light, abs light, etc? Have your alternator checked for the amp usage, they don't have to remove your alternator from your vehicle to test it. They just put the amp clamp device around the wire coming from the alternator to the battery and measure the battery while the engine is running and they can tell if the alternator is still functioning properly or if it is barely providing amps for your vehicle. Failing alternator might give intermittent problems or issues.

Another thing, I have not check our 1997 Mercury Sable 3.0L just yet but for most vehicle, it uses a crankshaft position sensor and it has wires going to the icm (ignition control module), just make sure that wire is not nicked or rubbing in the metal surface. Make sure that the spark plug wires are not touching the metal part of the engine. When I got our vehicle, I noticed our spark plug wires touching the valve cover and they are very very hot and that affects the electricity going inside the wire when they are hot. I moved the spark plug wires away from the engine/valve cover with wire separator and they are cool to touch now even after driving it.

When you say the spark plug wires looks ok. How long was the spark plug wires been replaced? It could be failing internally but not showing outside of the spark plug wires. When you pulled the spark plugs to re-gap it, are all of your spark plugs show the same condition? maybe one or few of the spark plugs may be still wet, etc., you can tell from the sparkplug tips itself if they being fired correctly with the right mixture of fuel/air or not.

Thanks Slade901. No other lights are coming on except the check engine light. When I reset the computer and run the car it initially blinks but when I turn off the car and start it again its solid. I replaced the wires at most, two years ago. I'm heading to the parts store today to get wires and plugs to make sure. When I pulled the plugs they all showed the same wear, significant. Okay, it might have been three years since they had been replaced. :-) I only pulled 4,5,6 because its hard to get to the rear ones. Tonite all of them will be replaced. I'll let you know how I made out tomorrow am. Thanks again. -- Peter

Hello Slade901,

New plugs and new wires had no effect on the diagnosis. Still giving P0300, Random Misfire, P0305 and P0306 Misfires on 5&6.

Blinking light is a missfire showing up in computer system
Check for actual missfire. Can you feel engine missing?
Check computer memeory for how many times it is missfiring.
If not there is a TSB on it 99-1-5 Jan 25 1999 for a pcm reflash.\
Another area to check is PID values and DPFEGR SENSOR
and LOW FUEL PRESSURE AND mass air flow sensor.