Start but no idle after CSV removal
 

After addressing the dreaded 'triangle of death' on my '83 SC this week I'm experiencing a major issue getting her buttoned back up. I elected to do a partial drop which was no biggie but had to remove the Cold start valve to get the internal thermostat free of its dwellings. I did not replace the O-rings on the cold start valve before reassembly and my big question is this, will this cause a big air leak? It seems I have a massive one because when started the car fires into life swiftly and thunderously then proceeds to drop to 200rpm before dying completely. I've checked and re-checked all the obvious hoses and vacuum lines but my mind keeps coming back to the CSV and those O-rings. I've got new O-rings on order but was just wondering if anyone had prior experience with this???

Justin

No prior experiences with the cold start valve causing a potential air leak?

Likely not causing a leak. You may have damaged the cold start valve. It is always a good practice to suspect the things you touched last.

you may have mistakenly pulled the hose off the block the csv is attached to.

Thanks for the response guys. I don't think the CSV is damaged because the engine starts after one crank just like normal but then quits after dropping to idle. I think once the engine has fired like that the CSV has done its job providing the initial charge of fuel. I'll do the "spray into a jar" test just to be sure. As for the vacuum going to the block, I don't think my '83 has the nipple on the CSV to connect a vacuum hose to the block but I could be wrong there, I believe only air it receives is from the Aluminum pipe connecting it to the AAR valve (pipe did get roughed up a bit during re-installation but no visible cracks etc). Looking forward to hearing more thoughts.

Could be your CSV is not shutting down or is leaking and the dying engine is due to overly rich mixture. Testing the CSV as you propose to do should determine if that's the problem.

Just tested the cold start valve and seems to be working perfectly. It sprayed about 1/4 of an once of fuel into the jar with no residual leaking. Im still suspecting perhaps its an air leak where the cold start valve flange mounts to the air box O-ring/gasket but I'm just not sure if these engines are that sensitive to air leaks to cause what was before an amazingly reliable CIS (really dialed in) system to not even be able to hold idle. Im kinda led to believe they are super sensitive to air leaks from what I've read on here. The Cold start valve is the only portion of the CIS I removed while addressing my 'triangle of death' oil leaks, hence why I am focusing on it.

Justin

Just,

My experience with something like this is it always turns out to be very simple. Something you knocked loose, or something inadvertenly left in place, or ....


Unfortunately, it is impossible to diagnose from afar. I can only suggest that you go back in, one step at a time, and double check all the places you have touched, and possibly have touched.

Did you remove the CIS runners,air box etc... from the engine? If so you must have reversed a hose possibly a vacuum line or disturbed the runner connectors or reinstalled a hose in the wrong place. Did you reconnect the brake booster line? Did you reconnect the throttle position switch? Did you reconnect the ecu harness for the o2 sensor?

Only way to know for sure what is going on is to test the fuel pressures and CO richness.
How much of the CIS system did you disassemble?
Maybe tightening everything up has it running really rich now.

Hey guys, not sure if there was some lag time between my last post and what you all posted but I did not remove anything from the CIS except the cold start valve and flange. Everything else stayed just as it was and I had absolutely zero complaints about my CIS before this so I'm thinking everything is how it should be. More than anything I was wondering if anyone has seen an air leak develop around the CSV after removal particularly if one does not replace the O-ring between the flange and the air box? I've got the O-rings and a new flange on order from our host and should have them in by tonight but just wondering if my theory on the CSV air leak has some validity. Thanks for the replies!

Justin

Air leak will normally raise idle speed due to a lean condition. Maybe you fixed an old leak with the CSV R&R???

If you did a partial engine drop you may have split the vacuum brake booster line? Just a guess but it sounds like you have a bad vacuum leak. How did you get at the breather cover and other components without removing the air box whilst the engine was in the car even with the partial drop? Just curious!

Cheated a bit, left the breather housing gasket for when I do a clutch or something else that requires the motor out. It was super dry on all sides, the thermostat O-ring on the other hand was so shriveled and sad looking it definitely wasn't doing its job. I'll double check the brake booster hose again, I looked at it in the engine bay area and it seemed tight and connected to air box but I did not follow it under the car. You think possibly split it further up underneath the car somewhere?

Cheers,

Justin

I remember a thread John Walker wrote I can't quote him but he was having a heck of a time tracing down a vacuum leak and he finally found it behind the sheet metal and it was a split booster line. A long shot I know but worth a look.

Thanks for that input. I'm at that point now of probably 10+ hours searching and trying different stuff to get it to idle right so I'm willing to try anything at this point.

plug on csv could be switched with freq valve?

Love reading old threads but this is an example of one that bugs me.

Lots of good back and forth and then.... nothing.

Surely justjones found this issue and corrected it. Please folks, post you fixes, not just your problems!

Regards

agreed... Super curious as what it was and how he fixed it.....2015 wasn't THAT long ago..

Lol, he did this:
http://forums.pelicanparts.com/porsche-911-technical-forum/975084-my-3-0l-under-knife-rasant-products-efi-conversion.html