Zinge

So my 911 is running very well when I start it cold, or within 5 min of shutting it off. But if I let it sit for 30 min or so, where the engine is still warm, then I try and start it up, it takes a few turnovers to get it to start. Once it's running I have to let it sit for a min or two while the engine throttles up and down by it's self. I might post a video of this when I get a chance.

I have been trying to do some basic trouble shooting on this problem, with no real direct indications in to the cause. The Fuel pump is running just fine. the spark plugs are set up just right, the timing is tuned. I was going to look into a new Warm Up Regulator. It feels like it's incorrectly balancing the of fuel to air ratio. Any one else have this same problem and fix it? Any suggestions? Thanks!

Older video of my car:
http://www.youtube.com/watch?v=F0IGYZk0AQE

Cold vs Warm Start:
http://www.youtube.com/watch?v=-qgqJa6HIDk

theiceman

well before doing anything I would do a base CO check . This is the most important thing you can do as it affects idle and starting conditions. If you say it only does it warm there are a few things you can start with
if your car has an O2 sensor I would start there is it controls a frequency valve which will affect your idle. Pure non warm start on a CIS car is more often than not the accumulator is bad ( failing to hold fuel pressure as you are getting no cold start assisit) but since yours is starting that may not be it , there is a hose on the bottom of your accumulator to provide vaccum , pull it off , if fuel comes out it is definitely bad as the diaphrgm is shot.

hunting ( up and down) is normally indicitive of a rich mixture so i would definitely get the CO checked first

Good luck

theiceman

Didin't sound bad in the clip .. or is that your way of showing us your car instead of a pic ? if so very imaginative and welcome aboard ... just checked and apparently your car DOES have an O2 sensor and frequency valve so I would start my troubleshooting there . Quite a few guys here have experience with this and I am sure they will chime in and tell you what to check . I would just get an O2 sensor myself then you know it is new as it is a maintanance item anyway and I think there is something you have to reset behind th dash ..

Zinge

Thanks Iceman! Yeah I might as well replace the o2 sensor. That's the way I have been trouble shooting things on this car... if It might be broken get a new one cause it's probably 30 years old and needs replacement any way. And yes the video was instead of the photo. ^_^ I will try and post updates as I fix this problem, so that any one else who has the same thing will know what to do.

Brad W

what about the cold start valve? Could that be suspect?

TroyN

Yes. The motor can also hunt when it's lean so as someone said, check your CO to figure out which is the problem.

theiceman

Not likely to be the cold start valve if it starts cold fine . If it is only a warm start I would say accumulator or O2 circuit issues. Never heard of lean causing hunting but i guess anything is possible .

ivangene

the video didnt help me as it seems to run fine on camera.

any chance its a fuel pressure issue? (trust me I know nothing of the cars - still learning and just "asking")

originalmotorhead

What needs reset behind the dash? Just curious?

Tom

Zinge

Yeah the video is of the car after it's been warmed up and still running. I will post a new video of the problem this weekend. The video was just my way of posting a picture of my car.

TroyN

If the cold start valve never shuts off, or leaks, then it would be rich when warm. Unfortunately the valve is pretty much impossible to get to w/o dropping the motor, but I think it's not common that they fail in that way. You can pull the wire from the temp sensor to see if that makes any difference. Check the operation of the (always forget, is it aav or aar, but see this thread):
https://rennlist.com/forums/911-foru...alve-long.html

You really should get a cis troubleshooting guide, maybe this'll help: http://members.rennlist.com/jimwms/CIS/CIShome.html

theiceman

Troy you are right about the access to that valve .. pretty well an engine drop situation .. theorhetically could you clamp off the fuel line to the valve after it has started cold and see if the problem persists when the engine warms up ? might help eliminate this as a possibility

wpriller

Sounds like the warmup regulator to me, I use to have the same problem and I replace my warmup regulator with the Unwire Tool UTCIS V pressure kit. I haven't had any problems starting my car, hot or cold.
www.unwiredtools.com

Zinge

http://www.youtube.com/watch?v=-qgqJa6HIDk

theiceman

Excellent post .. more guys should post like this who are having issues. A couple of thigs got my attention right away . Sounded like you had to give your car gas as you were starting even when cold. It reved right as it was starting. You should be able to get in a stone cold car turn the key and it wil start.
On the warm restart it was the same situation but the gas wasn't enough to keep it goingg 9 warm engines are always harder to start anyway and need more gas.

I would suggest checking your fuel pressures as mentioned for starters. I think you may have an issue in both cold and warm starts, but the aid of the cold start injector is getting you going when cold and is not there while warm .

The other major thing to check is your base CO . This setting is used primarily for starting and if this is not right then you will have starting issues. Although you need tools to set these, it would be better than shot gunning parts. Pete and Steve have a TON of experience with this stuff and I am sure once they see the vid they will be able to chime in with way better advise than mine .. good luck ..