Pelican Parts Forums - CIS advice needed

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CIS advice needed

Having a few minor issues with CIS on my 1982 SC and wanted to confirm with the experts my plan of attack.
Symptoms:
On cold start sometimes it will take 10-20seconds of cranking to start. Once it catches at first it puffs and chugs for a second or two (almost like a pfft pfft back through the airbox) before the engine really starts. Other times it will take only a second of cranking before it starts. If the car is already warm, it will start virtually by touching the key.
Cold start never idles at more than 1100rpm before settling down to 950 after a few minutes.
If I start to drive off within the first few minutes, I will get some slight sputtering and hesitation. If I wait for 4-5 minutes and then drive off there is no real hesitation or sputtering.
Once the car is warm, the idle will raise to 1100-1200 rpm and not come back down to 950.
The car will sometimes have a slight hesitation around 2200-2400 rpm under load (seems to be only in 2nd gear?), otherwise the engine runs beautifully through all rpm ranges and gears.
When I had the headers off a few months ago, I noticed that the exhaust port on number 6 had a darker color than the others which were more whitish.

I realize that there might be a number of things going on here so I thought I should check all the components:
Fuel pressures
Vacuum leaks
Injectors
CIS tuning (AFR etc.)

For the pros out there, where would you start and what am I missing?
Thanks

Quote:

Originally Posted by 997at (Post 9544498)

Having a few minor issues with CIS and wanted to confirm with the experts my plan of attack.

Symptoms:

On cold start sometimes it will take 10-20seconds of cranking to start. Once it catches at first it puffs and chugs for a second or two (almost like a pfft pfft back through the airbox) before the engine really starts. Other times it will take only a second of cranking before it starts. If the car is already warm, it will start virtually by touching the key.

Cold start never idles at more than 1100rpm before settling down to 950 after a few minutes.

If I start to drive off within the first few minutes, I will get some slight sputtering and hesitation. If I wait for 4-5 minutes and then drive off there is no real hesitation or sputtering.

Once the car is warm, the idle will raise to 1100-1200 rpm and not come back down to 950.

The car will sometimes have a slight hesitation around 2200-2400 rpm under load (seems to be only in 2nd gear?), otherwise the engine runs beautifully through all rpm ranges and gears.

When I had the headers off a few months ago, I noticed that the exhaust port on number 6 had a darker color than the others which were more whitish.

I realize that there might be a number of things going on here so I thought I should check all the components:

Fuel pressures

Vacuum leaks

Injectors

CIS tuning (AFR etc.)

For the pros out there, where would you start and what am I missing?

Thanks

What Year? Cold start could be WUR. Could be as simple as the electrical connection.
Dissimilar port color could be injectors (have cleaned and tested) or could be fuel distributor. Start simple - baseline with pressure check, injectors, vacuum leaks etc, then get more complicated (read expensive)

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Quote:

Originally Posted by Charles Freeborn (Post 9544503)

Oops.......1982 SC. Thx.

Quote:

Originally Posted by Charles Freeborn (Post 9544503)

What Year?

Charles, 1982 from looking at other posts OP made.

A functioning cold start valve will start the cold car immediately if the basics are present. I would say, as a rule. Look into this first.

The CSV sprays when starter is cranked. 20 seconds of cranking will saturate/flood the intake system if no ignition. I am not really sure if it goes the full 20 seconds, but it sprays when the starter spins.

I know I did not address the bulk of your concerns. You asked what to start on.

Just be patient.

Find the 82 electrical diagram. Look at Part 1, page 1. Starter and CSV. Well, half the CSV. You have terminal 15a from the starter to the CSV. CSV to Thermo time switch. Looks like two wires. I believe TTS only creates ground for the CSV to spray. Too hot, ground is killed. No fire.

Porsche 911 Electrical Diagrams (1965- 1989)

Quote:

Originally Posted by Bob Kontak (Post 9544554)

Agreed. CSV first, along with routine diagnostics. Then proceed from there.

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CSV
cold control pressures
air leaks.

as bob said, the CSV will give it that initial firing which it does not seem to have.
air leaks and/or hi CCP can make it seem like the CSV is not working but will make it run bad after it first starts up. if too lean that will also cause low idle not to mention the back firing.

try turning the key on, then lift the air sensor plate for a few seconds then start it. (cold).

Make sure both terminals are connected on the thermo-time switch.

Thanks guys. I'm going to start with CSV first. Makes perfect sense based on your feedback. I hope to get to it this week and I'll report back. Thanks again. Man I love this board. I also love Porsche for making these cars and the following of addicts like us.