Start Problem

Jorgeman · Jorgeman's Garage

My '86 911 has just started a new problem. Some history: The engine has always started on the first 1-2 revs and settled into a smooth idle almost immediately. I had a 60K full service done in Sept.and the car ran flawlessly on a 2400 mi. high speed dash up to Yellowstone and back in early Oct. Two days ago, I noticed the start drill had changed. After the car has sit for 24-36 hrs, it still starts very quickly but seems to be rough and rocking for 5-6 seconds before settling into a smooth idle. The rest of the day all starts seem normal. I suspect pressure to the injectors is bleeding off over time. I've also noticed an increased gas smell around the car in the morning. Is this a known problem? Does anyone on the BB recognize the symptoms? Would appreciate your ideas and/or fixes! Thanks in advance.

scottb · 10-17-2002, 04:13 PM

Have you replaced the O2 sensor or the idle control valve yet?

Jorgeman · Jorgeman's Garage

Quote:

Originally posted by scottb
Have you replaced the O2 sensor or the idle control valve yet?

Scott--no to either. Could you explain the theory behind your query? What function does the idle control valve perform? Would it "heal" itself after 4-5 seconds? I'll do some searching in my books to learn more about it's operation. Thanks for responding.

dickster · 10-17-2002, 11:09 PM

my '86 starts straight up but "hunts" for a few seconds and then settles to smooth idle. sounds similar.

nothing to worry about.

Jorgeman · Jorgeman's Garage

Quote:

Originally posted by dickster
my '86 starts straight up but "hunts" for a few seconds and then settles to smooth idle. sounds similar.

nothing to worry about.

Dickster--I'm concerned because this is a sizeable change from it's operation the past nine years. It almost sounds like the engine is starting on one, then two, then three cyls before it finally seetles down into it's idle. These engines normally start so fast that there MUST be a pressure maintained at the fuel rail for the injectors. I believe that pressure is somehow leaking off requiring the fuel pump to re-establish it before the engine lights off. Could that be caused by an injector leaking? What-
ever it is causes the smell of gas to be fairly strong when I get in the car in the AM.

911X2C · 10-17-2002, 11:49 PM

I have a 86 911 also, during the spring and summer months, the engine starts and idles smoothly after a couple of seconds. As the weather gets cooler, I notice that the engine will idle a little rough for about 5 seconds and then settle into a smooth idle.

The behavior your describing sounds perfectly normal. Hope this helps.

Lee

dickster · 10-18-2002, 12:03 AM

what about if you turn the ignition on for a fe seconds before starting - let the pump build up pressure??

the fuel smell is not normal and a bit worrying. i had a smell that turned out to be the line out of or by the pump leaking, you might want to check that and other lines. easy to do 'cause they'll look "wet".

good luck

scottb · 10-18-2002, 04:38 AM

The O2 sensor should be replaced every 60,000 miles. I'm not an expert by any stretch of the imagination, but my understanding is that it plays a part in fuel mixture. What you're describing sounds like a fuel problem, and if the sensor is going bad it's possible once it heats up it "rights" itself a bit and the car begins to perform normally. Since the manual calls for replacement at 60k, if you have that kind of mileage and haven't replaced it yet, it's worth doing.

On my 84, I had a problem where intermittently the car would fluctuate at idle between 800 and 1100, up and down, up and down. I replaced the idle control valve, and the problem went away.

Both of these are relatively easy and inexpensive "fixes," and present a good place to look before you begin looking at more expensive and complicated problems.

dickster · 10-18-2002, 10:48 AM

02 sensor only works when engine is warmed up, but the idle control i dont know...........

marcesq · marcesq's Garage

If you 84 is wired right, the fuel pump only turns when the key is in the start position or the car is running.

If you can smell gas there must be a leak or fumes are escaping from the return circuit. Points to check are the the rubber line from tank to pump, pump banjo fitting, fuel lines that run from front to back through tunnel, the connections to the charcol box, and many fittings in the engine bay.

Let us know what you find.