|
|
|
|
| Author |
|
|
Registered
Join Date: Aug 2012
Posts: 488
|
Delayed Acceleration
Working through some gremlins on a 77 911S...
on acceleration, especially in first, the car accelerates as one would expect, and then really launches (probably around 2K RPM). Almost like another bank of cylinders coming online. It's not running rough, or missing prior, but definitely feels like something is online, all of a sudden. Any ideas or culprits folks have run into? Just starting to go through it, so have an order of air filter, spark plugs, etc., and may learn more as I go.
__________________
J 911 SC - 1980 911 S - 1977 Last edited by Guardsred911; 07-04-2017 at 06:00 AM.. Reason: title |
||
07-04-2017, 05:58 AM
|
|
|
cycling has-been
Join Date: Sep 2004
Location: Jersey Shore
Posts: 7,238
|
Several of your symptoms point to a vacuum leak.
You may be dealing with multiple issues. Bill K
__________________
73 911T MFI, 76 912E, 77 Turbo Carrera |
||
|
07-04-2017, 06:54 AM
|
|
|
Administrator
Join Date: Aug 2016
Location: Los Angeles, CA
Posts: 6,087
|
If you're going to be testing for vacuum leaks, take a look at the link below for a helpful guide. Best of luck!
Porsche 911 Vacuum Leak Test | 911 (1965-89) - 930 Turbo (1975-89) | Pelican Parts DIY Maintenance Article |
||
|
07-10-2017, 04:12 PM
|
|
|
Registered
|
I just went through days of troubleshooting these symptoms: hesitation to about 2,600, good pull afterwards. After CIS adjustment, it would run better at lower rpm, but misfire at higher rpm. After a lot of fussing with fuel system (had it running OK at high, but idle was horrible/stall) I finally found a cracked filterbox by accident: when I put put my hand and some weight on the top of the filter housing idle improved markedly. Pushing down on the filterbox sealed the crack. It's probably the simplest way to eliminate that possibility if you are willing to play with CIS adjustment and idle. The crack will allow air into the engine that is not registered by CIS and result in lean combustion.
There may be other ways to check for a cracked filterbox. If there is no pop off valve installed, there's a good chance of it cracking from an innocent misfire. |
||
|
07-10-2017, 05:40 PM
|
|
|
Registered
Join Date: Oct 2006
Location: MYR S.C.
Posts: 17,321
|
do you have a blowoff valve in the air box.
check timing/advance(s). do you know if any nods were done to the engine. (cams) been quite a while since I had my 77 but are you just experiencing the power band coming in?
__________________
86 930 94kmiles [_  _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
||
|
07-11-2017, 04:58 AM
|
|
