Cold Start Problems

Argeo · 05-08-2003, 05:36 AM

Hi, looking for suggestions on a cold start problem. Here is what happens when I try to start. First, it takes about 4 or five tries to get the motor to stay running. When I do eventually get the car to run, it feels like it not running on all cylinders, the engine putters at about 500 rpm very quietly, then with a little help from the gas pedal I get the RPM's to rise up to the 1500 - 2000 rpm range. The reaction in not instant when I put my foot on the gas, it seems to take a few seconds for the RPM's to shoot up. I then back off on the gas lowering the RPM to 1000. As this point, the car most often backfires out of the pipe as it does when it is at 500 rpm's. Occasionally I would hear the pop off valve opening during this start up process, though I think I fixed this by riching the system a bit through the Warm up regulator (WUR). After the car finally settles down at 1000, the RPM's do not bounce around on deceleration which I guess happens when the car is running to rich. When the car is warm it runs great, starts great. I have changed the plugs, the fuel filter, air filter and tinkered with the WUR and the air flow plate height.

Could it be fuel pump or sparkplug wire related? This problem has plagued my car the whole 2.5 yrs I have owned. Any suggestions appreciated. Thanks in advance.

jason2guy · 05-08-2003, 06:33 AM

sounds like your AAV is not open when cold.

Argeo · 05-08-2003, 06:41 AM

Hi Jason, thanks for the response. Now the AAV is at the right side of the motor (passenger side), behind the airflow meter and gas distributor. I believe two hoses feeding into it. Someone in the past had told me that AAV can be eliminated from the system by plugging off. I didn't plug off but are we talking about the same thing. If so, how does that valve get the power to open and close? It does make sense that the car at start up is getting to much gas and not that little bit of extra air that is needed. Where the valve is closed, the valve runs good when slightly warm because the valve is stuck shut where it should be when the engine is warm.

Am I correct?

Thanks.

Argeo · 05-08-2003, 06:58 AM

My bad. The AAV is the valve on the right side of the motor just above the right valve cover. Is there some way to test this. Also, doesn't this valve open and close based on the temp of the motor which is why it is located where it is?

Thanks.

jason2guy · 05-08-2003, 07:29 AM

your right. its on the right side and there is a power connection going to it. contrary to popular belief the valve NEEDS power in order to close.
the engine heat IS NOT enough. i know this because i just went through 5 new valves thinking they were faulty and all that was wrong was a DIRTY connection. it was mind boggling because i thought that the engine heat would be emough to close it.

if i were you id take it off and inspect it. most likely you'll find that yours is stuck shut, at least that what it sounds like. if thats the case you can either drill out the rivets abd take a look inside or just buy a new one.
its easy to R&R

jason2guy · 05-08-2003, 07:30 AM

youre right. its on the right side and there is a power connection going to it. contrary to popular belief the valve NEEDS power in order to close.
the engine heat IS NOT enough. i know this because i just went through 5 new valves thinking they were faulty and all that was wrong was a DIRTY connection. it was mind boggling because i thought that the engine heat would be enough to close it. but it isnt

if i were you id take it off and inspect it. most likely you'll find that yours is stuck shut, at least that what it sounds like. if thats the case you can either drill out the rivets abd take a look inside or just buy a new one.
its easy to R&R

Argeo · 05-08-2003, 07:33 AM

Thanks again. What do I need to take the valve apart. Is it just screwed together?

Thanks.

ChrisBennet · ChrisBennet's Garage

It is riveted together. I drilled out the rivets and replaced them with screw when I repaired one of these this winter. Mine had a broken spring.
-Chris

azasadny · azasadny's Garage

Well,

A fellow "Pelicanite" came over this AM to try and help me figure out why my car won't start and we did the following:

1. Confirmed that we have spark at plug #1
2. Confirmed that we have fuel at the injectors
3. We towed the car and popped the clutch in 2nd gear and the car started, popping and backfiring the whole time and when I pressed on the gas pedal, the engine immediately died.
4. We sprayed starting fluid in the airbox and it still wouldn't start.

Could a "bad" cold start valve cause this. Any suggestions as to what to do next?

azasadny · azasadny's Garage

I replaced the cold start valve and thermotime switch last summer when the intermittent cold start problem began. Today, I was able to get the car started after replacing a wire splice from the throttle microswitch to the solenoid (old wire was in ver bad shape). After driving the car about 15 minutes, the car started easily, after sitting 1 hour the car will not start again. I'm back at "square one" and I only hope I can get the car started again to drive it to the shop and let a "professional" look at it since this problem is obviously beyond my meager abilities. Thanks for your advice, I've gotten lots of good advice, I just can't get the "root cause" of this problem resolved!

ruf-porsche · ruf-porsche's Garage

In your 5-10-03 post you said that you couldn't even get it to start with starting fluid, after you tried tow (push) starting the car?

Have you done the basic such as test the compression in all the cylinders? If you got spark and spray starting fluid into the airbox it should start unless something like no compression is the problem.

I had a 1974 911. When it wouldn't start I would always check the point in the distributor. Have you check the point and determine if they are gap right? Also check for pitting and see if they are burned. Points get burned when people turn on the car without starting the engine just so that they can listen to the radio.

With the new electronic ignition in the newer carsw, people forget about the maintenace required for an older car. Most people don't even know what points are.

azasadny · azasadny's Garage

The original starting problem has returned. I managed to start the car after about 50 cranks and several loud backfires, then it started and ran great. I drove it about 60 miles to a Porsche event and I stopped at a gas station. Restarted the car with the first crank. After letting the car sit for 30 minutes, it's extremely difficult to start again. I'm goint to test the pressures using my recently acquired gauges. I'm going to search the PP archives for the testing procedure and take it from there. I'm not going to start replacing parts again and evidently my mechanic didn't fix the problem, so I don't think I'll be taking it back to him.

azasadny · azasadny's Garage

Many of you have followed my intermittent "cold starting" problem that eventually became a constant starting problem that caused my to have to crank my car 20-30 times, with several loud backfires, prior to the car starting. Once the car started, it ran great but the starting problem was driving me nuts. Needless to say, I replaced alot of components (fuel filter and accumulator, cold start valve and thermotime switch, throttle microswitch, plugs, CD unit, rotor, coil, Pertronix unit, WUR, etc...

Each replaced item improved the situation temporarily, but the problem still persisted. The cold and warm pressures were within acceptable limits and I had good spark at plug #1, but the car just cranked and refused to start. To make a long story short, this is what the mechanic found:

- The plugs were improperly gapped (too wide) even though I followed the instructions on the PermaTune CD unit for spark plug gapping specs.

- The plug wires and their "boots" are bad and I will replace them

- The "new" throttle microswitch that Jordi Riera sent to me worked perfectly and the old one was bad

- One of the wires coming off the Pertronix unit had rubbed until the insulation was off and bare wire was showing.

My mechanic "fixed" these things and the car starts on the first crank, idles at 950rpm and runs great. I REALLY appreciate all of the assistance so many of you have provided. I have learned alot from you kind folks. I'll post this update on the other posts that I have been on so that anyone with a similar problem may be helped. I had checked the spark at plug #1 and had a nice spark, but my mechanic showed me that others were weak. I hope this helps others out there....