99 996 Hard to Start When Cold

My 99 996 for the last couple of months has been starting hard when it's cold or I haven't driven it in a week. Once it's warmed up, it starts fine. I did see on a post on here about a fuel pump going bad. I have just replaced my battery and my starter was replaced last year, along with the wire that runs from the starter to alternator, just so everyone knows those issues have been fixed for the warm starts I have had before. The car runs great once it's running, no rough idle or anything. Any ideas would help.

I've been having a starting issue with my 1999 996 (about 95,000 miles, automatic) since mid-November. Sometimes the car will start up just fine. Other times, with no rhyme or reason as to timing (sometimes cold start in the morning, sometimes warm start after car has been parked for 30 minutes to a few hours, etc.) the car does not want to start up. When I turn the key I will hear the "na na na na na" sound which could last up to 10 seconds or so. Then sometimes the engine will fire up and die right away. Eventually, after repeated starting attempts, the engine will start up. Otherwise, the car drives just fine. Yesterday, had a new symptom pop up. Was trying to start the car and then heard a "boom" behind me and white smoke coming from the engine compartment. No fire. Let the car sit for 5 minutes and eventually got it started. Car has been taken to multiple mechanics who either (1) can't replicate the starting issue after numerous attempts; or (2) have the issue but can't figure out what it is. First time around, Porsche mechanic (independent shop) was able to recreate the issue once and told me that fuel pump needed replacement. After replacing the fuel pump, problem still happened. Next time around at a different Porsche shop (dealership), mechanic could not replicate the starting issue, did a full inspection of the car, and told me that the ignition coils needed replacing because of hairline cracks so we replaced all the coils as well as the spark plug. Problem continues. Any thoughts would be appreciated. I've dumped close to $2000 on repairs between the fuel pump and ignition coils and don't want to do any more repairs until someone can tell me the problem. Thanks much!

Are you getting any CEL, misfire codes, or fuel system warnings? You live up north and cold start enrichment is rough on these 20 year old cars. Could be several things.. MAF sensor , aging Fuel Injector (i.e. poor spray pattern), plugs need to be replaced. etc. etc.

I had a starting issue on my 2000 996 several months ago. Also changed the fuel pump but the issue was still present. Symptoms were a bit different from yours. What initially appeared to be an intermittent starting problem turned out to be a repeatable starting problem after every gas fill up. Turned out to be some pressure valve in the gas line. I would need to pump the gas pedal like crazy to get it started. Replaced the valve and no problems since then.

I just had my coils and plugs replaced last year as one had misfired and made the car run terrible. When I say "cold start" I just mean from it not running for a few days in 25 degree weather. I've never had the problem before this year. I'm getting a fuel pressure test done in a couple weeks. The car runs great once it's started, just turns over 4 or 5 more times than it should when first started.

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Quote: Whenever either my Boxster or 996 Turbo did that it was a sign of a low battery. The car and especially the battery doesn't like to sit unused in cold weather. But in most cases it was also a sign of a going bad battery. Then in one case it was due to the Turbo alternator some minutes after engine start its output dropping off. I observed the battery voltage gauge reading drop from very near the 14V hash mark to the nearly 12V hash mark. Took the car in and the tech confirmed the alternator was the problem. He installed a factory rebuilt alternator -- 2 year warranty vs none for other alternators.

I replaced my battery 4 months ago. My volt gauge is at 14v. I will mention to check the alternator. Again, it's not really a "cold start", just starting after sitting for a day in warm weather.

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Quote: Replaced a battery in my Turbo. 5 months later the new battery was dead. Bad battery. Got a new battery under warranty. Just to emphasize this but even though the initial battery voltage reading appears good and ~14V is "good" -- it may not stay there as you drive the car. As I mentioned in my previous post my Turbo battery voltage fell as I drove the car and the problem was a bad alternator. It would work at cold start and shortly after but as the engine ran the alternator output fell. In your car's case it could be a too large a electrical drain. Something in the car is drawing more electrical power. Be sure all the interior lights are off. I had a case where my VW Golf was showing signs of a weak battery over time and I found -- almost by accident -- someone had turned on one of the reading lights in the back seat and this was on all the time. Another possibly might be a trunk lid light staying on even if the trunk lid is closed. Be sure there is nothing plugged in to one of the car's power outlets. I once left my Boxster parked for a week with a code reader connected to the OBD2 port. After a week the battery was almost dead. Bad enough while it would light up the dash when I turned the key on it would not start the engine.

The 14v does stay there as I drive, maybe the needle is just under the 14v white line but a needle's width. There are no lights on as I took the bulb out of the trunk 4 years ago so it wouldn't ever get left on. I'm going to get things checked out on Monday. Maybe the battery is bad, I have had that happen in other vehicles. It turns over fast but it just turns over about 3 or 4 more times than it used to and it's almost like I should give it fuel, like an old carbureted vehicle and it starts.

I'd check the fuel pump relay .

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Quote: It is important to know what the battery voltage is after the car has sat a while. My recollection is the tech would check the battery voltage first thing in the AM then check it just before close of business. In some of these cases while the battery voltage would be ok in AM by quitting time it would be low. James suggestion to check the fuel pump relay is I think a good one. Techs have a bypass relay to use to eliminate the relay being a problem. You can order one of these from the dealer parts department, at least one could and I did. But when it came in someone else needed it -- some kind of emergency -- and I was asked if he could have mine and I said yes. To avoid me having to order and wait for another one to arrive a tech loaned me his bypass relay.)

Great ideas and I will pass them along to the tech. Also, can someone tell me where my ECU/DME is for my car? I have googled it and I can't seem to find a straight answer as it's not behind the backseat on a C2.