87 325, Idle problem

[XLT03]

Help!!! I have an 87 325, auto with 112,000 and it started to have a bad idle. Would stop at traffic stop and suddenly car will die. Restart and it would be fine for a few seconds and it'll die again. If I restart and kept foot on gas it'll stay running but if I take foot off gas it'll die. If I keep foot enough on gas to prevent it from stalling I can drive the car. Does anyone have any idea on what is the problem?

Thanks in advance.

[Filehorse 525i]

With that many years and miles, the first place I'd be looking is for a vacuum leak in a hose somewhere. If that's the problem, it'll be the cheapest thing to fix...!! If it runs fine once you get off idle, a vacuum leak is a good bet. Here's hoping.

[cntrouniv]

Hi,
I am having a similar problem with a 95 318ti. It has only happened recently. I am new at this and am sort of interested in fixing the problem myself. What is the vacuum mechanism you are refering to?

[Filehorse 525i]

Under the hood, most of those smaller diameter black hoses are vacuum lines. They control multiple devices such as the cruise control, fuel regulator, power brake booster, and a myriad of environmental stuff. A break or crack in any of these hoses causes the fuel mixture at idle to lean out to the point the engine will either idle very rough of may not idle at all. A thorough visual inspection coupled with a hands-on inspection of as much of the tubing as you can reach is in order. The most likely locations for cracks/breaks is any location where the vacuum tubing connects with a fitting or connector. These connections stretch the tube and may cause it to fail after many years of prolonged exposure to engine heat. The tubing is not rocket material and you could probably use some from your local parts store but you want to be sure to use the correct size. Given the relatively inexpensive cost of the sutff, you might want to just pick up enough from your BMW dealer to replace the all the vacuum hoses as a matter of preventive maintenance. Given the age of the car, if you don't already have a failed vacuum hose - you will eventually. Hope this helps.

[Filehorse 525i]

Originally Posted by cntrouniv

Hi,
I am having a similar problem with a 95 318ti. It has only happened recently. I am new at this and am sort of interested in fixing the problem myself. What is the vacuum mechanism you are refering to?

Oops. Didn't realize you were NOT the one who posted the original question. However, everything still applies to your situation although a 95 vintage should still have vacuum hoses in good condition. That said, I'd still take a good look at them though since it doesn't cost anything to inspect and you just might locate the problem. Unfortunately, there are also a sack full of other things which could also be causing your idle problems - none of which will be as cheap as a vacuum hose but you probably won't have to get a note from your banker to fix it either.

[XLT03]

firehorse 525i:

Thanks for your input. I'll change them all and you're right it's not that expensive. Also is the air balancing valve a suspect item to keep an eye on?

[Filehorse 525i]

There is a laundry list of other possible suspects for rough idle - everything from dirty injectors to gummed-up intake valves to the fule pressure regulator to the idle control valve. At idle, the combustion air bypasses the throttle butterfly via idle control valve. If this valve is not operating properly or if there is a leak in the hoses, it will cause the problems you are experiencing. The good news is that since this problem came up rather suddenly, it's probably NOT the injectors or the intake valves. Happy hunting.