Ok, the details '01 E430 79,XXX miles, maintained, car has not been driven much since premium is over $4...
Cold start misfire out of the blue about three weeks ago set code P301, warms up runs OK (not missing, but not it's usual silky self)
Couple more cold starts everything OK. About a week ago cold start running really rough sets P300,P301,P304 comes up to operating temperature still missing. Pull in parking lot shut down and restart, everything OK (at this point wondering; what the flip did microsoft make the ECM for this thing...) Tonight, cold start ROUGH Set codes P300, 301, 304 up to operating temp..a little better, pull in parking lot clear codes and shut down and restart, OK again. Have an independent AUDI mechanic (its either the local dealer that is notorious for charging you for work they never perform, driving three hours to the next nearest dealer that is honest, or him...) that has a live scan tool but basically knows enough to only be dangerous. What to look for as he scans it? and any ideas of common problems of this symptomology could be on this particular car?

 

Ok.
Lets see if I can help.

P0300 is a Random multi cylinder misfire. Not much help.
P0301 and 4 are Cyl 1 and Cyl 4 misfire. i.e. we have two cylinders misfiring on the RH bank (as viewed from inside the car).
The situation resets and clears with an ignition off but returns.

You do not state whether the CEL is on or not. I would have expected the CEL to come on. Does the CEL warning light illuminate at ignition on. i.e. the bulb is working?

Maybe the car is going into "Limp Home" due to a significant misfire and you are thinking that the limp home characteristics are a misfire. Maybe not?

Now a misfire can be caused by numerous things but the fact that a reset temporarily clears the problem suggest that the RH bank has a bad spark, is going weak following some electronic adjustment by the ECU or maybe faulty fuel injector.

Firstly I would want to be sure that the engine service schedule is up to date.
Not sure what the recommended plug change point is but best way around this one is to change the plugs and possibly also the leads around (bank to bank?) and determine whether this has any impact on the cylinders misfiring. Make note of where components were originally so that if necessary everything can be returned to original locations. I suspect this process may not be successful BUT you will have avoided the cost of new plugs and prevent introducing new possible causes by using non OE plugs and leads etc.

OK. So its not the plugs and leads. Of course it could be a coil pack and this could be eliminated using a similar process.

Next I would try to capture the conditions under which the misfire is initiated. Is it following a hard or moderate acceleration or irrespective of however carefully you drive?
A good scan tool will allow you to read the "Freeze Frame" data that set the CEL, if indeed it is on?

I suspect your misfire only shows up after a significant acceleration demand of some sort.
This takes us back to why just the RH bank.
Unlikely MAF, fuel supply or CPS Crank position sensor, temp sensors (common to both banks) so maybe its an injector / injector connector.

So does the injector wire harness appear to be in good condition. These are known to degrade?
If visually OK try swapping a misfire cylinder injector around. Can you get the misfire to move?

If not we are beginning to run out of common issues.

If indeed it is the MAF I would have expected a P0170,1,3 code but you have not identified these codes.
A MAF is quite expensive and it is pointless changing it unless we are really out of ideas and every thing else has been eliminated.

OK so we now move to the next suspect the RH O2 sensor.
I personally find these to be extremely reliable and don't advocate changing them without good reason.
Personally i would observe the waveform (need a live data scanner) to ensure that the voltage coming off the sensor is correct and that the frequency of the waveform is correct. If you are in DIY territory again, and without an appropriate scanner, you could try swapping the LH and RH O2 sensors. Does the misfire code move?

Next you have to consider an inlet manifold leak and cylinder pressures. More about these once you have been through the other ideas.

I guess I have given you enough ideas for the moment. Misfires can be very expensive to track down unless you are methodical in your elimination process.

Let us know how you get on,

Stuart

 

O.k., thought couple things would be evident but it is my fault for not clarifying...all problems are at cold start and 60% of the time resolve once up to operating temp 40% of time need to clear codes and shut down / restart to resolve...MIL triggers on a few seconds after start when missing. Car misses at idle/under load when doing it, although can be solid miss or as it warms up become intermitant (as in sitting at idle smooth 3 seconds, miss miss, smooth ten seconds smooth, miss miss, so on and so forth (hope this illustrates what I mean....) Once resolved would call idle 98% smooth, no blatant miss but not its silky self (i.e. you can tell it is running by the, what would be "normal" amounts of vibration if it were say a GM product)....drove last night first time in about a week and a half, see previous post for what it did, drove today no cold start issues, no miss...also put about 200 miles on it today and she is her normal self the idle is so smooth hard to tell if it is running or not....Driving it seems to help a lot, but sitting a week to two at a time still shouldn't cause these symptoms....
Thanks

 

So what did you do to improve matters?

Suspect the miss is due to EHT breakdown somewhere so many of my suggestions remain valid.
Basically can you get the miss to move cylinders by moving components around.

Stuart

 

The answers are 1. What have I done? Answer, nothing, only driven the car. One more only if to chalk up I guess, it does not act up if it gets driven everyday and the couple hundred miles of driving seemed to smooth it out...nothing done to the car mechanically. 2. Get the misfire to move around? Car is not acting up, systems normal so can't experiment when it's running fine. Seems on the surface to be a component such as an injector, EGR valve that sticks, or even a fuel pump relay/regulator that at cold start after the car has sat not being driven for a week or two which resolves itself 98% on reaching operating temp. and 100% with a good drive under her belt....

 

As I say its likely a coil, plug, plug lead or injector.
If you move these components about and determine whether the next time the problems happens if it has moved from P0301 / P0304 to lets say P0306/ P0307 after moiving plugs from 1 and 4 to 6 and 7 you have your answer.
If the problem has gone for good then problem solved till it reappears.

Stuart.