altarchsa

Well my 964 is finally back on the street after about 6 months of being up on stands for a rebuild. I can't believe it took me so long to get the time to finish the project.

The car runs great! Except for the usual couple of issues that always seem to follow a major rebuild. This time its the speedo, a problem which I have in my sights, and a hard cold start, on which I'm not really sure where to start.

The car starts and runs great when warm. But that first start in the morning is almost impossible, sometimes running the battery down before I have to jump it and crank some more to get it started. By the way, it doesn't even have to be that cold. The pic is for grins. The hard start occurs even when its 60 degrees.

It seems like a stuck open cold start sensor. The motor will crank for several seconds before showing even any signs of life. Then it will kick over like its going to start before dying immediately. It seems like it floods out. If I depress the accelerator, it's even worse.

This continues for several minutes before it finally starts to stumble and chug, eventually dying over and over. Finally, it catches enough that I can race the engine a little, if I'm careful and catch it just right. If left to idle in that first 5-10 minutes it will eventually die. It takes 10-15 minutes for it to fully warm up and idle a little. After fully warm, it idles steady and runs great.

Any suggestions. If there's a fix, I know from past experience it's on the way from my Rennlist friends.

elbeee964

Congrats! (Well, sort of...)

I remember when I accidentally left my ISV disconnected, it acted the same way.
Bet it's something electro/computer related.
That whole, "it runs great when warm" disinclines me to suspect anything mechanical.

(O2 sensor? some engine temp sensor?)

Anyway, Rennland will get this figured out for you! -and Merry Christmas!

ian89C4

(rebuilding my engine, getting ready to start putting things back together)

DWS964

My first guess would be the idle control valve is "stuck" (I discovered this problem on my C4 after it sat for a few months) or not connected (yup, did that...), or the idle micro switch is not "on" when cold (perhaps due to the accelerator cable being too tight and requiring a bit of adjustment). Look at the switch to make sure it is making contact with the throttle, and that it is connected. Use a Scantool if you have one - it will tell you if the Idle switch is On. I recall reading that you must not have your foot on the gas when starting, or else the ecu will not know how to idle the car once started due to it's reference point for the throttle position. But, I am no expert.
I just researched this yesterday, as I have a similar but not as severe problem with cold start. Search for "idle switch" and "throttle adjust".

Hope you have a Merry Christmas!

elbeee964

Great points, Darrell.

Indycam

Hows your cylinder head temp sensor ?
If you give it a shot of starter fluid does it run on the starter fluid ?
My guess is that its "lean" on start up because its not being run rich enough for the temperature .
Its like not pulling out the choke on an older car .

Colin 90 C2

could be your fuel pump check valve.
try jumpering the fuel pump at the dme relay before cranking. then put back the dme relay and crank the starter to see if it starts.
or an easier way is to check your fuel pressure at the schrader valve on the fuel rails. I don't know the value it should be, but I'm guessing somewhere around 50 psi.

Keep us posted.

altarchsa

God suggestions, all.

I know the head sensor / wiring got some abuse because I left it in the head when I cleaned it. (Didn't take it out because I didn't need valve work as this was another rebuild following one within the year due to a failure in only one cylinder.)

The ISV could be the problem. I didn't relaize it could cause these symptoms - Thought it was just idle control. I cleaned it a year or so ago but maybe it locked up during inactivity.

Anyone else wanting to add their ideas will be appreciated. Could help me decide where to start and save time.

ian89C4, Good luck. I have so much fun working onthat motor, but this time I hope the repairs give me longer uninterrupted fun driving time.

Driving this car again is a blast!

Thanks again!

altarchsa

uh, I think you guys are great, but not that great:

I misspelled Good......didn't mean God!

springer3

Read the diagnostic codes. That is by far the easiest way to find bad or disconnected sensors and actuators.

darth

Check vacume lines for leaks and the rubber tubes on the intake secured by band clamps.

Hope this helps
Bill

hellspcangel911

OP, i have the same issue on my car, runs great off starter fluid, but lots of cranking to get going. Did you find what the problem was?
thanks

Marc Shaw

A blocked carbon cannister would also cause such problems and it is only used when the engine is cold.

Marc

hellspcangel911

Is there a way to test if its the carbon canister? just unplug it?
thanks, Marc

Marc Shaw

Yes, you could just unplug it (towards the front of the left rear wheelwell) but be careful as you'll have gas fumes vented there with all their inherent dangers.

Marc