Rough idle near stall, once SAP cuts out in cold weather

[Tonyfeb14]

My '03 4.4 X5 starts fine in cold weather (below 35F). It fast idles with the Secondary Air Pump running (new SAP). But as soon as the SAP cuts off, about 2 minutes after starting, the idle is very erratic until the engine gets up to operating temperature. It idles at about 500-600 RPM and the throttle doesn't always respond well until the engine temp is near normal operating temperature. A blip of the throttle and the engine can stall. If its too cold, I can get some flashing of the service light as I detect some misfires. Once warm this all clears up.

It seems like it's running too lean as it just comes off the air pump, or the air pump should stay on longer than 2 minutes. But I assume no adjustments are possible?

I am open to ideas as to what is going on. Once it gets to operating temperature it runs great.

[andrewwynn]

Do you have N62 or M62? The symptoms sound like intermediate levers or the setting for min valve height is out of whack.

I’ve never seen the procedure online because the only set of directions I’ve seen online is behind a paywall.

There is a tool free valvetronic reset procedure I would find that and start there

[Tonyfeb14]

This is the M62 4.4 V-8. The N62 was offered starting 2004. Not sure what "intermediate lenders" you are referring to, a typo? Thanks for the reply, I will search around for a valvetronic reset procedure.

Not sure why anything would suddenly change, but I did have the car laid up for quite a few weeks in my garage that started with replacing alternator, then morphed into water pump, valley pan, valve cover gaskets, new MAS, new SAP, etc. but it all went back together weeks ago and is running fine except for this new problem that started in the cold weather.

[andrewwynn]

Levers. Typo. Doesn't apply to you with M62.

I helped rebuild a few M62 and every one needed at least one cam position sensor replaced after putting back together.

Do you have a scanner that shows you realtime cam positions?

[Tonyfeb14]

I have an iCarsoft i910-II which shows all kinds of real time data so I should be able to read the cam positions. I just need to know what to look for. As an aside, I found a "procedure" when I Googled. It was to turn ignition to position 2 and fully depress the accelerator peddle 10 times in 15 seconds to reset the valvetronic. Sounded like hokuspokus but I did that this morning. The ambient temp is now around 45F so not as cold. The car starts fine, stays on the SAP for 2 min and idle was higher, around 650-700 RPM when still warming but off the SAP. As it was warming up the idle improved, steadier. I cant tell if the "procedure" made the difference or not since its about 10 degrees warmer today.

[andrewwynn]

M62 doesn't have valvetronic uses regular vanos.

Are you getting error codes?

Look though your scanner for cam position. Should have a requested and actual. I can plot a graph overlay with foxwell scanner and it's very helpful in finding problems.

Do you get a rattle in you engine at at start up that fades away? M62 notorious for having problems when the chain tensioner sort fails. Often it will rattle at start up but when it finally throws a code it's usually a timing error when the cam advances in it's own do to slack in the chain.

I could see this leading to bad idle. Similar to soft fail cps.

[Tonyfeb14]

The car has been running fine with no error codes. There is no chain rattle on startup. Starts normally and SAP cuts out in 2 min or so. But in cold weather, once off the SAP, its a very rough idle. If I let it idle to warm up, a miss can develop on multiple cylinders and creates an error code. With all the errors thrown, there is also a code on Signal on Camshaft position. But once it warms up, it runs fine. I can clear the codes and no code again, until next time when starting in very cold water. It was 7 degrees F the other day when I let it warm up and I got all the cylinders misfiring. Then cleared right up to a stable idle once warmed up. When I check the camshaft position on bank 1 and 2, I see -.014 degrees CR, and -.03 degrees CR. Not sure if those are in range but apparently the position sensor is reading camshaft position. Maybe the camshaft position sensor?

[andrewwynn]

it's a unicorn to ever see an actual cps error. Unless it's alrwady new OEM start with replacing.

If y8ir scan tool can read realtime cam positions y8u should be able to show requested and actual at the same time and see if they track properly.

My foxwell will graph them on the same chart makes It really obvious and the cam angles will change many times per second.