I bought my 530i a little over two years ago. During the warm months the car runs perfectly but when it gets cold the car won't rev past 2500RPM when first started. After driving the car for about half an hour the car will rev to around 3000RPM and after about 45 minutes the car might start operating normally. I have a manual and don't have a problem with this when driving around town for the most part but its downright dangerous on the expressway.

When the car reaches these RPM "limits" it feels like hitting a brick wall, the check engine light comes on, and I need to pop the car out of gear and let the RPMs wind down before accelerating again.

I was getting a code from the mass air flow sensor and decided to change it. It gave me a nice performance boost but didn't solve the problem. I've also checked the throttle positioning sensor and it seemed to be working properly. Fuel filters are brand new and I don't think there's anything wrong with the fuel pump. Like I said the car runs perfectly in the warmer months but I've had this problem for two years now in the winter and I can't take it anymore. Any help would be much appreciated, thanks.

Wow. Could be something with the ECU? Something sticking in the throttle or throttle body or something like that?

If you are seeing a CEL there's a stored fault in the OBD. What fault is being registered?

What is the idle like? So it is a temperature-dependant drop in power, or does it shut off?

I will check the fault codes right now and see what I come up with.

The idle is perfect. The problem seems to be dependent on the temperature in the engine compartment, not the temp of the engine. This will happen even when the temperature gauge is in the middle.

I have a '94 530i I actually just took mine in to the shop for almost the opposite. Mine will not hold an idle at all when the temp is below 30 outside. It has a vicious idle if it can manage to stay running and won't keep running unless the rpm is 700+. Occasionaly while driving it will surge and the CEL will go on. I'll let ya know what my mechanic determines the problem is and see if it may be related to yours.

I will check the fault codes right now and see what I come up with.

The idle is perfect. The problem seems to be dependent on the temperature in the engine compartment, not the temp of the engine. This will happen even when the temperature gauge is in the middle.

Here's list of fault codes if you need em.

http://www.bmwe34.net/e34main/trouble/engine_codes.htm

The crankshaft position sensor could be on the outside range of its operational parameters, such that the thing gets a better reading as the bracket holding it expands due to heat, moving it into operational spec.

There are few things that cause what you are describing, mechanical or electrical.

I'm not coming up with anymore fault codes. I had the one for the MAS but after clearing the codes and replacing it I haven't come up with anymore.

If it was the crankshaft sensor shouldn't I experience some stumbling or lagging from the engine? I'm just wondering if there are any other symptoms of a bad crankshaft sensor I could look for. As it is it runs very smooth it just kills itself as if I'd redlined it. Its as if the car thinks the throttle is open far more than it is. That's what made me think the TPS was bad but like I said I check that with the meter and it seemed to working fine.

bump

Update: called my mechanic and my problem was a faulty fuel pressure regulator.

interesting - let us know if replacing the regulator solves your problem.

I had an odd stumble at idle and a CEL that I couldn't track down for the longest time - ended up being an intake leak after the MAF. All it required was a couple bucks worth of hose clamps to fix the leak and voila! no more cel.

interesting - let us know if replacing the regulator solves your problem.

I had an odd stumble at idle and a CEL that I couldn't track down for the longest time - ended up being an intake leak after the MAF. All it required was a couple bucks worth of hose clamps to fix the leak and voila! no more cel.

That's what the mechanic thought originally. He was also concerned b/c my tank has a dent in it. He figured it shouldn't be a problem w/my tank -moreso on an older 3 series b/c of the placement of the lines ie fuel return.

I was lucky to cuz it's only gonna cost me $135 all together. I was fearing other issues granted I really hope this solves the problem. Now I need to wait for it to drop below 30 outside. That's when I'll tell if it fixed the issue.