‘01 4.4i misfiring when cold
 

Hello,
Recently my 2001 4.4i has been misfiring but only when cold. I keep reading codes and they all seem to be random misfires with fuel cutoff. I changed the spark plugs and installed new Bosch platinum plugs (figured it might be a good idea as the car has 122k miles) but this did not solve the issue. It misfires upon start up and when cold, but once the car is warmed up it runs fine. Can anyone help me pinpoint the problem?
Thanks

Any "lean" mixture codes? Thinking a leak in any of the intake hoses or vacuum lines. You might want to do a fuel pressure test. Odd that it only does it when cold. And, at this point, the injectors come into question as well.

No lean codes, just the misfires... I’m really not sure what it could be at all. I remember this happening last winter once or twice, but once I cleared the codes back then the issue went away despite the freezing weather in NY. Now for the last few weeks it’s been on and off again. There is no rough idle when it doesn’t misfire though, so I didn’t think it could be a vacuum leak. Regardless, I appreciate the feedback

Leaking valve cover gasket into the spark plug area?

intermediate levers? Does the misfire go away after a restart?

it's an 01, M62 not N62.

:thumbup:

The valve cover gasket is leaking but I’m not sure. When I changed the spark plugs there was oil on the plugs for the back two cylinders of the bank on the driver side (not sure of the bank and cylinder and numbers)

The misfire sometimes goes away after restart but more often than not, the problem persists until the engine is warmed up

Since you have multiple misfire with fuel cutoff, goes away once the engine is warm I would say that it is not an ignition misfire but a weak cylinder misfire. A weak cylinder misfire is when the cylinder doesn't produce the same amount of power as the other cylinders. The computer can determine this quite easily by the rotational speed of the crank once the spark plug has fired for that cylinder. All the other cylinders could be rotating the crank at 700 rpm but one could be rotating it at 650 or 630, etc... You will not notice the difference but the computer wil know.

In that case I should definitely take it to my mechanic. Hopefully it’s not that (sounds expensive😒) the thing is that it’s random cylinders... would they be all be weak then?

A weak cylinder could be a cylinder with low compression (expensive fix) or a vacuum leak (lean mixture) could cause a weak cylinder. The fact that it goes away when the engine is warm leads me to believe it's a vacuum leak. Could be a hairline crack that opens up when it is cold (material contract except for water) and closes up (expand when it is hot).

I’m beginning to think it is a vacuum leak. I let the car get cold and just started it up with the hood open and I hear a hissing sound... from past experience I know this could mean there is a vacuum leak, but is a hairline crack still a possibility? The hissing sound eventually goes away and is only heard when the hood is open, but it is currently not misfiring.

you have to do a "smoke test" of the intake system. Try to break this down into one thing at a time, systematically. As I said in one of my earlier posts, gas, air, spark. Verify one at a time. Go on Youtube for a description of what a smoke test is

The cheapest smoke test can be found on Scotty Kilmer's Youtube Channel. Cheap as long as you stay away from the Cohiba. LOL

My bet is the intake manifold gaskets. When mine started to go bad it would run like crap on cold start then smooth out as it got warmer. replaced the gaskets and all was fine.