A/c blows warm check engine light flashes 98 mercury

Improper spark plug gap
Damaged spark plugs
Poor contact between wires and spark plug or cap or coil pack
Bad insulation on plug wires
Cracks or corrosion build up on cap and rotor
Weak or defective coil(s)
Weak or defective ignition module
Weak or dirty crank sensor
Timing
Fuel pressure (from pump)
Clogged fuel filter
Defective injectors
Vacuum leaks
Defective injector drivers (computer)
Poor compression

That is all I can think may causes engine to misfire.

_________________
Autel MaxiDAS DS708

Code # 301??? That is NOT a valid Diagnostic Test Code (DTC) for the engine control system on a 2000 Mercury Sable.

Assuming that you mean P0301, that is a cylinder misfire code that is identifying number 3 cylinder as the cylinder with the misfire problem. MANY things can cause a cylinder to misfire including spark plugs, spark plug wires or boots, burnt valves, broken valve springs, blow head gaskets, cracked cylinder heads, bad or dirty injectors, faulty injector control circuits, Failed ignition coils...the list goes on....proper diagnosis required.

1st, replace your spark plugs(for gasoline engine) or heater plugs (for diesel engines)

if this does not work, have a mechanic check the timing of your engine. Engine timing is checked in the distributor, camshaft, and crankshaft.

Hello Sdhesseltine.

The flashing check engine light is telling you the engine is misfiring and your description of the problem confirms that.
There will be a code stored in the vehicles engine computer that will tell you which cylinder(s) is/are misfiring.
Spark plugs, ignition coil, fuel injectors or internal engine problems will cause this.
If it has been a while since your last tune up it would certainly be a very good place to begin.
The usual tune up stuff, spark plugs, air and fuel filters for the basics.
A fuel filter will not be at fault in this case but is part of a tune up on this model.

If you require further advise, please ask me here in comments, be glad to help.
Thank you for using FixYa.

KL

stop by local parts store (Autozone,Advance, etc) and have them do a free fault code test. They can print out a list of faults and clear the codes

The power output stage hi and low (basically the ignition module) this is what powers the coil and can cause misfiring if not working properly.
This is located by the computer (e-box) it has 4 plugs, 2 on one side and 2 on the other.
Other possible issue for misfire are: loss of compression bad injectors electrical problems bad ECU

Hello K Martin.
A flashing check engine light indicates engine misfire.
Misfire will reduce power.
Misfire is usually caused by poor ignition (spark plugs, wires, ignition coil).
These are the first things a mechanic will check.
If they are OK then fuel systems will be looked at.
After that usually mechanical items such as timing components, valve train etc.
If you are a handy fellow and it's been a while it may be a good time to replace spark plugs and ignition wires.
Hope this helps you solve the problem.

Thank you for using FixYa.

KL

A multi misfire may mean that one or more of the following has happened:
Faulty spark plug or wires, Faulty coil (pack), Faulty oxygen sensor(s), Faulty fuel injector(s), Stuck/blocked EGR valve / passages, Faulty camshaft position sensor, Defective computer.

The engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wire, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the the problems were faulty fuel injectors. 

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

Good luck and hope this information helps, keep me posted, be glad to help you get the truck running 100% again. Not sure if your running a K&N air filter, and if you are there may be a flim of oil on the MAF sensor that is making you run lean. You may want to spray down the MAF sensor with a can of MAF cleaner. 

It sounds like you have a misfire. Anytime a misfire is detected by the powertrain control module (PCM) it flashes the check engine light (CEL) on and off. Do not drive it this way because it won't take long to damage the catalytic converter. Have the diagnostic trouble code (DTC) read with a scan tool or "code reader" to see what DTC or DTCs are set. If it's a 4 cylinder, it will have a P0301 set for a cylinder # 1 misfire, a P0302 for a cyl # 2 misfire & so on. If the misfire is random (ocurring in multiple cylinders intermittently) it will have a P0300 set. Once you know which cylinder is misfiring you can check that cyl to see what the cause might be. It could be an ignition coil or spark plug failure. The # 1 cyl is always the one closest to the front of the eng or this car, the one closest to the passenger side fender.

There are three kinds of gasoline engine misfire scenarios, first there is the "under load" misfire and there is the "at engine idle" misfire, and finally there is misfire continuously. All engine misfires exist because one of three things has occurred. First, a cylinder has lost compression, a cylinder needs a certain amount of compression to operate correctly. Second, the ignition system has failed or is failing intermittently, spark is needed at the time of compression to ignite the fuel air mixture. Third, the fuel air mixture is incorrect, proper mixture is needed for the ignition system to ignite fuel properly. If any of these conditions occur in the engine, the engine will misfire.
1. Low or no compression can be caused by

a. burned or leaking intake or exhaust valves
b. worn or broken piston or piston rings
c. worn out camshaft
d. wrong weight motor oil was installed holding the cam followers from adjusting
e. broken valve spring
f. failed head gasket.
2. Ignition system has failed or is failing
a. spark plug has fouled or is worn out
b. ignition coil
has failed
c. spark plug wires have shorted
e. engine control module coil driver has failed
3. Fuel/Air Mixture is incorrect
a. vacuum leak at the intake manifold
b. fuel injector has failed
c. EGR valve is stuck open
d. mass air flow sensor has failed
e. oxygen sensor has failed
f. air intake boot is cracked

common problems:
1. fuel injector has failed or is failing
2. spark plug wire has shorted
3. spark plug is worn out or is cracked
4. ignition coil has failed is failing

Testing a coil on the car is pretty easy. No special tools are required. Just remember to be careful, the amount of electricity generated by your ignition system can be dangerous. If your coil is already off the car, or if you would like a more specific data-driven test, you can bench test your coil. To set up the test, remove one spark plug wire from its plug, then remove the spark plug using a spark plug socket. Next put the spark plug back into the spark plug wire. Be careful not to let anything drop into the empty spark plug hole -- very bad.