Multi cylinder misfire at low rpm only

At and near idle misfires/rough running that seem to clear up with acceleration are very often lean misfires from a vacuum leak of some kind. The rhythmic "clanking" part doesn't sound good and suggest worse things. But I'd start by looking for vacuum leaks, including around the intake manifold. With the CEL flashing, I would not have the car in service until you figure it out.

Of course, another possibility is just a dirty MAF sensor. So I guess I'd actually start with a good MAF sensor cleaning and then move on to vacuum leaks.

 

I had this happen and it was a vacuum leak on the left side of the intake manifold


iPhone ?

 

Sounds ominously like a third gen, with failing head gasket; try a leak down test?

 

Post #4 is making use of the information that misfires are reported, and third gen head gasket issues can present with misfires as symptoms.

Post #2 is making use of the information that misfires are reported, that they appear at high vacuum/low load, disappear above idle, and reappear on return.

Because Josey and Paul's suggestions are making use of more of the information from the original post, that might be the angle I would pursue first.

When the ECM decides whether to light the check-engine light or to flash the check-engine light, it's in fact running a calculation of how severe the misfiring is, how much unburned fuel that leaves in the exhaust, and how hot that will make the catalytic converter. If the calculation comes out "hot enough to destroy the converter", the light will be flashed. That's the background behind Josey's suggestion to limit use of the car with that light flashing. The Gen 1 converter's an expensive part.

 

I've not had a vac leak in this car. It was Paul Schenck (post #3) who said he had those symptoms and found an intake leak.

How are you searching for the leak? They can be very hard to find. Do you have a vacuum gauge by chance? A lot of people spray flammables around intake and hoses. Most anything including WD40 would do. Or they do hiss so a length of hose in your ear fished around the intake and lines/fittings can sometimes pinpoint them.

 

Good suggestions, but to the OP: how long has this problem persisted? Has it been rainy in your area before the problem started?
More than one tank of gas?
That was a good initial bit of debugging, new plugs & swap coil packs.

I offer the possibility of water in the fuel from a corroded fuel fill pipe (see thread "Random Misfire Codes P030x").
Some HEET or DryGas in the tank; run the fuel level down as low as you dare, then refill partway with premium. Repeat.
Inspect for how much rust or damage there is on the fuel fill pipe.
This is now a 20-year-old vehicle...
Bro. Chapman linked to an older thread on the same kind of problem.
Sounds a LOT like the problem that my daughter had.