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Old 06-20-2022, 08:00 AM
BrianVA-911 BrianVA-911 is offline
 
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Default Injectors, Alternator, Fuel Pump Or Something Else?

I have a somewhat still new to me 83 911sc targa (155k miles) and I am hoping you all can troubleshoot an issue I am starting to see more frequently. It isn't a daily, but I try and get it out at least once or twice a week. Lately I have noted that on cold start ups, its starts right up but the RPMs stay under 1k until things warm up and then it idles at 1k. My biggest concern though is that by the time I get it backed out of the driveway and into 1st gear, I will give it more gas and it seems really laggy for a few seconds and then it either gets enough fuel or whatever the issue is corrects itself and off I go.

I have also noticed the tach bump on random occasion, which I believe is a sign the alternator is on its way out but not sure if the two are related

So the big question is, is the lagging on the cold starts related to the injectors, the alternator, fuel pump, or something else? Any info would be appreciated. Thanks.
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Old 06-20-2022, 11:46 AM
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CIS injectors are mechanical and easy enough to test if you are inclined. Pull them out one at a time, put them in a small container and with ignition on trigger fuel. Keep in mind the seals and cups are likely brittle and due for replacement if not done already. You can see spray pattern and measure volume of fuel with this test. Not scientific but generally close enough to ID a significant issue.

Dont underestimate the impact of a vacuum leak, worth spending time with a simple smoke machine or a flashlight and some carb cleaner. Also, I might suggest testing o2 sensor output and mixture to get a better idea of current state.

Battery issue. Confirm battery connections and ground strap are in good shape. test battery, charge if required, before jumping to an alternator.
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Old 06-20-2022, 08:57 PM
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Dont underestimate the impact of a vacuum leak, worth spending time with a simple smoke machine or a flashlight and some carb cleaner. Also, I might suggest testing o2 sensor output and mixture to get a better idea of current state.

Sounds like a vacuum leak to me, but Cmartin is correct, could be all of those issues.
Do you have any service history on the engine? Do you notice a difference in vacuum when you remove the oil cap while the car is running?

If you think it's a fuel related issue with the CIS, this video has a ton of info:
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Last edited by catron1; 06-20-2022 at 09:44 PM.
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Old 06-21-2022, 07:51 AM
BrianVA-911 BrianVA-911 is offline
 
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Thank you both for this great info. I will get into this once I finish up with a move I am in the process of going through right now. It kills me to have my small 1 car garage stacked with moving boxes around the car, but thankfully I am upgrading to a 2.5 car garage so it will be worth it.
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Old 06-22-2022, 01:24 PM
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Never saw half a car before I saw Jazz cut a 964 in half. Lol
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Old 06-22-2022, 07:13 PM
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Quote:
Originally Posted by BrianVA-911 View Post
I have a somewhat still new to me 83 911sc targa (155k miles) and I am hoping you all can troubleshoot an issue I am starting to see more frequently. It isn't a daily, but I try and get it out at least once or twice a week. Lately I have noted that on cold start ups, its starts right up but the RPMs stay under 1k until things warm up and then it idles at 1k. My biggest concern though is that by the time I get it backed out of the driveway and into 1st gear, I will give it more gas and it seems really laggy for a few seconds and then it either gets enough fuel or whatever the issue is corrects itself and off I go.

I have also noticed the tach bump on random occasion, which I believe is a sign the alternator is on its way out but not sure if the two are related

So the big question is, is the lagging on the cold starts related to the injectors, the alternator, fuel pump, or something else? Any info would be appreciated. Thanks.
This is exactly how my 911SC acted when the warm up regulator was failing. Ran fine once warm but had very poor acceleration until then
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Old 06-24-2022, 08:40 AM
BrianVA-911 BrianVA-911 is offline
 
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Quote:
Originally Posted by Parenn911 View Post
Never saw half a car before I saw Jazz cut a 964 in half. Lol
you aren't looking hard enough. lol

https://bringatrailer.com/listing/356-sculpture/
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Old 06-25-2022, 04:25 PM
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Originally Posted by BrianVA-911 View Post
you aren't looking hard enough. lol

https://bringatrailer.com/listing/356-sculpture/
wow
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