911SC cold start sequence

[NeunelferPNW]

I had a reputable shop in my area replace my CIS airbox etc. I drove it home and it was fantastic.
The next morning, I start the car and the cold start sequence just felt super off. The RPMs weren’t holding as high as I remember and drop to 950 RPMs fairly quick. Sometimes dipping below to 500-600. A blip of the throttle would cause the car to stall and it wouldn’t restart with out some manipulation of the throttle. When it would seem the idle had stabilized at 950-1000, the car would stall during gear changes or coming to a stop. Once warm, the stalling stops but there’s still times where the RPMs dip below the set idle. I emailed the shop today but haven’t heard back yet. I don’t think they would deliberately have let me have my car back not running correctly.

I DO own a Bosch fuel pressure gauge. I just haven’t gotten around to it 🥱

[theiceman]

well when you get around to it let us know..

or im sure the shop will say bring it back.

[NeunelferPNW]

Originally Posted by theiceman

well when you get around to it let us know..

or im sure the shop will say bring it back.

Just fishing for suggestions before I aimlessly replace every component without testing.

[EC900]

Here something from a few days ago:

2.7 CIS cold start issue

[berndtj]

I doubt it's a coincidence that this started just after having your CIS/airbox serviced. I would absolutely contact the shop as step 1. I wouldn't be surprised if a hose got knocked off. Hopefully, they make it right.

[silverlock]

Is the WUR to intake hose — which is just behind the airbox, to the left of the left (driver’s side) strap, seated correctly?

[PeteKz]

Originally Posted by berndtj

I doubt it's a coincidence that this started just after having your CIS/airbox serviced. I would absolutely contact the shop as step 1. I wouldn't be surprised if a hose got knocked off. Hopefully, they make it right.

Ditto this.

Do NOT throw part at the problem. And, do NOT change more than one thing at a time. If you give up, John Walker's shop is in north Seattle.

[theiceman]

yeah you wont have to replace parts aimlessly if you get around to putting your CIS fuel pressure gauges on it and give us your readings. Otherwise we are guessing just like you.

but first place is the place that did the work.

[boyt911sc]

Were you touching the gas pedal during warm up in the video? Get out of the car and try to start the cold motor by reaching through the open driver side window and turn the ignition switch to START.

Use your brand new CIS gauge to monitor the cold control pressures versus time and take note of the RPM (engine speed) up to the time CCP stabilized to WCP. The test will take up about 4 mins. no more than 5 mins.

Have you talked to the shop about your problem? Keep as posted.

Tony

[NeunelferPNW]

Originally Posted by boyt911sc

Were you touching the gas pedal during warm up in the video? Get out of the car and try to start the cold motor by reaching through the open driver side window and turn the ignition switch to START.

Use your brand new CIS gauge to monitor the cold control pressures versus time and take note of the RPM (engine speed) up to the time CCP stabilized to WCP. The test will take up about 4 mins. no more than 5 mins.

Have you talked to the shop about your problem? Keep as posted.

Tony

At the end I was pressing the throttle to kinda show what it does. I’ll be taking it in this week.

[NeunelferPNW]

Solved:
Incorrectly routed vacuum hoses between the warm up regulator, deceleration valve and manifold. Deceleration valve was adjusted as well.

[Hx911]

thanks for letting us know.
as an owner of a CIS 911 with startup problems I am happy about ANY information and solution

[NeunelferPNW]

Originally Posted by Hx911

thanks for letting us know.
as an owner of a CIS 911 with startup problems I am happy about ANY information and solution

No problem. I hope this information helps you and anyone else.

[boyt911sc]

Originally Posted by Hx911

thanks for letting us know.
as an owner of a CIS 911 with startup problems I am happy about ANY information and solution

Hx911,

These are the critical informations you need to test to fix your starting problem/s:

• Good ignition signal…….use an inductive timing light.
• Control, System, and Residual Fuel Pressures………..use pressure gauge.
• Unmetered Air……….……use a smoke generator.
• Etc.

Stop guessing and confirm the above items. We all started like you and should not prevent anyone from not being able to diagnose any CIS problems correctly. This forum has practically discussed and covered almost all known CIS problems known to exist. The problem is people do not apply the correct test procedures to identify the culprits.

Tony