normohl

My s4 misses when at a constant speed at around 20hgin and under real light acceleration and most of the time in first and second, it makes your head slightly jerk around. When i give it more gas its fine just normal driving its a problem.

My vag-com said cylinder 5 was misfiring and a couple other but not as much as 5. We pulled that plug and it was fouled so we replaced and still the same problem, it has spark and we can tell the injector is firing, we measured how much the fuel pressure dropped on the 5th injector and then tried the injector in front of it, and it dropped the same amount of pressure for both.

I have a vag-com but don't really know what measuring blocks to log where would i start

Here are the codes that it was pulling to start with, when i erased them they did not come back.

4 Faults Found:
16815 - Warm Up Catalyst; Bank 2: Efficiency Below Threshold
P0431 - 35-10 - - - Intermittent
16805 - Warm Up Catalyst; Bank 1: Efficiency Below Threshold
P0421 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16689 - Cylinder 5: Misfire Detected
P0305 - 35-10 - - - Intermittent
Readiness: 0000 0000

EuroXS4

Depending on your year of s4 either try changing icms if you have a early s4 or if you have a late model.put the coil from the cylinder thats misfiring to another cylinder and see if the misfire moves.If it does then the coil is at fault.If it doesnt you could have a possible issue inside that cylinder.

normohl

its a 2000 we tested compression on that cylinder and it was fine. Cylinder 5 coil was replaced and all the others were original.

I called the performance shop that the previous owners brother and father own and he said he thinks its the injector on cylinder 5 but both injector 5 and the injector in front of it dropped the same amount of pressure when pulsed 100 times. that's when the car is not started. If i remember it was from 52 psi to 25-30 psi in 100 pulses of each.

Peter Badore

Were the other miss firing cylinders 4 and 6?

normohl

I think it was on 4 and 6 also yes just not as much.

Peter Badore

Maybe the ignition control module for bank 2 is starting to malfunction. Sometimes the ICM will be intermittent before complete failure. Audi does not call them POS (Audi's actual nomenclature) for nothing. Have you switched the two ICMs with each other to see if the misfire moves to bank 1?

normohl

is the ICM easy to get to, would a normal mechanic know how to get to them and switch them side to side?

If the ICM was going out why would it misfire more on cylinder 5 and less on the other two on the drivers side?

it just seems fishy that the coil on cylinder 5 is replaced and that's the cylinder that's misfiring the most.

EuroXS4

If you have misfires on 1 bank it normally is the ICM.Why some cyliner mis more than others that I cant say for sure.But if you have 1 bank misfiring the icm is most likely your culprit. icm sit ont othe the airbox on the passenger side of the car you can replace them yourself if you have the part.easy as pie.

normohl

so just switch the two sensors on the airbox?

jordonb

Swap the two icms and see if the misfire follows. If not, move the coil from cyl 5 to another one and see if the misfire follows that.