Cold start idle issue
 

This problem turned out to be a cracked vacuum line.


I have a 1995 318ti with 52,000 miles. This past summer engine was professionally tuned...new plugs, wires, cap, thermostat, battery. Replaced cracked intake boot with a new one. Running really well, very smooth, great fuel econonmy.

Now that it is winter the car has a cold starting issue. Immediately upon starting engine in cold weather, I simultaneously need to manually bring up to a fast idle speed for about 15 to 20 seconds...then slowly let up on the gas pedal and cold engine will idle roughly for about 30 seconds...then it smooths out, warms up properly and runs fine. Issue not present when starting warm engine or starting cold engine in warm weather.

If I don't manually bring up the idle speed simultaneously with cold starting, the engine will fire and start but immediately die.

Is there some sort of cold starting fast idle sensor that needs to be changed? Some other type of cold start senor, etc.? If there is an identifiable part that I probably need to change, will you please state its name for me so I can order it on line and install it?

Thanking you in advance for informed suggestions!

Mine does this too and I'm waiting for my new hood shocks to arrive so I can get in there and diagnose it. The consensus on the old Yahoo group and to some extent here is that this problem is caused by a vacuum leak. There are a lot of vacuum lines under the intake manifold and a couple of big ones that attach to the rear of the intake and the valve cover. None of these hoses have clamps on the ends, they're just friction fittings. The theory is that cracks develop in the ends of these hoses over time and they are exacerbated by cold temperatures. As I said, I've not verified that this is the problem on mine, but I hope to have time to get in there sometime soon. It's probably worth the effort to take a look and see if anything's obviously wrong, although you can't see a lot of the lines without removing the upper half of the intake manifold. Go to realoem.com and search for "distribution piece" to see a diagram of one of the suspected culprits. Hope this helps. Either way let us know if you solve the problem.

Could it be the secondary air pump? I know that it only runs for the first 30sec when the car is cold. Here's a thread about rough idle, post #13 has some good info about it.

http://www.318ti.org/forum/showthrea...ndary+air+pump

Check your air filter.

95's don't have secondary air pumps

You check that air filter yet?

A mouse is nesting in there to get away from the cold!

D'oh, good catch.:doh:

Anyone get a solution to this yet? My car started doing this last winter, and it got so bad that the car would barely start when sitting at -5F and colder.

I have just ordered almost every single vacuum hose, intake gasket, o-ring and seal from Pelican and will fully rebuild the whole intake assembly before fall.

For cold start problems, Haynes lists:

Battery dying
Terminals corroded
Air Filter clogged
Plugs gapped wrong
Low compression
Fuel/ignition problem

William, can you specify which vacuum line was cracked, causing the problem?

Yeah, sorry to bring this up again, but my 98' 318ti sounds like a diesel for around 30 seconds on cold mornings, but is totally fine when warm. Sometimes it feels like it 'overstarts' if that makes any sense? Normal starting you here the starter motor crank and theres a definate point when the engine catches. Sometime it seems to half start midway through the first crank but then idle horribly.
This is all in cold weather though, so any pointers as to what vacuum hose you replaced would be appreciated.

Just called my mechanic to get accurate information.

He said the leaking hose that was a problem on my car attached to air cleaner. It allowed air to leak in after the mass air flow sensor, so the computer did not adjust for the extra air. He said to carefully check the hoses from the air intake and mass air flow sensor to the engine. He said some of the hoses are corrugated and they develop cracks in the grooves.

Hope this helps you out. Happy Thanksgiving!

The main air intake hose seems to be pretty common for cracking on the 318ti. Mine cracked and it seems like people are replacing them all the time.