Hey guys i being working on a 2004 volkswagen passat came in with several codes p0411 p0171 p0300 and p0302 all of those codes are gone except the p0302. The problem is that the misfire only happens for around 5 to 10 seconds in the morning and then its good all day spark plug was swap same with coil and injector
I’d first verify with boroscope (after cold-soak) that no coolant was entering combustion chamber. I then would analyze the ignition waveform (obtained from a high-tension cable between COP and sparkplug) and monitor for activity.
I’m not intimately familiar with this vehicle so I don’t know if it is of a GDI fueling strategy but certainly possible that carbon may be the culprit .
Since the problem only happens once per warm up cycle, start your problem analysis with a relative compression test. Use an ignition sync from the #1 ignition coil trigger, and give it about a 20 second crank. This will rule out any valves sticking.
When you were swapping spark plugs, did you do it before the engine was started and was there any color difference between any of the plugs?
On that engine, and for problems like that, I always current ramp the coils. You can open the harness that feeds the coils at the rear of the engine and garb all 4 wires with your current probe. This will give you a parade of all 4 coils.
If perchance you have a plug that is being fouled, you can see the problem here, and its quick and easy. Being this problem only happens once per warm up cycle, there is a very good chance something is fouling the plug.
Agree with Brandon and Albin
I'm old-school simple so what I'd do first is to motor the starter for about 10 seconds after its sat overnight, without allowing the engine to start and yank the plug. If it's is wet, you've found the likely problem.
There is a software update for cold misfires. Refer to TSB 01-09-09.
Can you take a look at the intake valves for carbon build up, Have you monitor the mass airflow and is it a factory original sensor? Not getting unmerited air from any elbow rubber fitting hoses under the manifold with a crack fracture
what is live data measuring block values on group 14&15 misfires
is rear main seal leaking?
When i swap the inyectors i look inside and the valves look clean also i smoke the engine to look for leaks nothig found
when you smoke intake you have to put about 5 psi regulated pressure to find small leaks otherwise they will never show, can you post some scan data of mass airflow
I'll have to agree with a possible coolant leak during a cold start. You should be able to get it hot and let it cool off and check that cylinder for coolant before you start it. I've seen the intake ports crack numerous times on these.
It's not a GDI, so those common issues are thrown out.
It's preferred to check fuel trim with a scan tool that can check the measuring block data, because the car gives you an idle and part throttle LTFT, and generic data combines them. You can find that in measuring block 32.
As stated before, the misfire measuring block you are looking for is in block 15 for cyl 2. You can watch that and block 16 to see individual misfires on the cylinders when first starting.
There are often a lot of various vacuum leaks, take a close look at the vacuum hose to the secondary air hose combi valve, that could be causing your SAI fault as well as contribute to your lean condition. I see one way vacuum valves go bad, but typically cause misfires on all cylinders.
These cars have a readiness test plan that is super easy to run and set. Basic setting block 77 will run the SAI to check that.