Continuing to sort out my CIS system

JSZ · 08-08-2018, 05:10 AM

When I have an opportunity, I have been working on my 911, trying to address some of the issues I have. Within the last 2 months, I upgraded the ignition to a MSD 6AL digital, Clewett Engineering braided wires and new cap and rotor. I also have spent a great deal of time cleaning the fuse box and other electrical connector components.

I took the car out last night for a short drive. Car started right up and was idling at 950-1000rpms. After a short warm up, I noticed this when driving. It has small hiccups at cruising rpms and this is more intermittent. I also have some issues with the idle and at times will rise to 1600 rpms and then after some driving it settles back in the 900 range. It does not fluctuate other then it stays high or lower.

I installed a AFM gauge and it appears the engine maybe functioning correctly. At idle, 12.5- 13.5, cruising, 14.0 -15.9 and acceleration 12.8-13.5. Of course this is fluctuating rapidly. But in theory the CIS system and the O2 system are doing what they are supposed to?

Unfortunately, I wish I had more time to work on the car and enjoy it. But life...

Thanks for any advice and thoughts.

T77911S · 08-08-2018, 08:12 AM

you might look for a leaky injector.

if you really want to get into CIS invest in
fuel gauges
a hand vacuum pump
timing light
dwell meter

the dwell meter will tell you if your FV/O2 is working as it should. also used to set AFR
vac pump can test hoses, DV, AAv
you need to set timing before setting mixture. also checks advance
gauges, you need to know fuel pressures before adjusting mixture.

if you really want to make it right
remove CIS, new injector sleeves and Orings, rubber boots on runners, hoses, new injectors, new o2sensor.
if you really want to go deeper, rebuild the FD and WUR.

it will be good for another 40 years.

HarryD · 08-08-2018, 09:17 AM

As in all things related to fuel Injection, before you mess with the CIS parts, be sure you ignition system is operating correctly. Do a full tune up: points, plugs, cap, rotor, set the dwell, set the timing, verify your advance to 36 degrees is working. Once these are spot on, you can consider looking into the CIS part.

petrolblue83911 · 08-08-2018, 09:25 AM

Agreed on last comment;

Look for a fouled plug

JSZ · 08-08-2018, 11:52 AM

All good questions and advice, I will add the following.

Relative to tools, yes on everything except still trying to find my dwell meter that is packed away.

The car is an 82 Sc and when I purchased it, it had sat for some years with around 55K miles. I rebuilt the engine , ( with help) from the case up. O ring s were replaced to the injectors, however I was advised to leave the plastic retainer. Injectors were cleaned and then checked with a Bosch injector tool, all excellent. Rubber boots were all replaced, airbox was checked. FD and WUR were rebuilt and finally recalibrated by Tony. Warm conrtol pressure is 3.45 bars and system pressure is 4.9 bars.

During the recent MSD install, the new Bosch plugs were replaced with NGK's plugs and a new Bosch O2 sensor was installed. I do have to say when installing the plug wires, I did not get a click on all of them, which I thought was odd.
I am thinking of servicing the distributor, uncertain if I really have the skill set. So I have yet to go tackle that one.

I can add more detail if needed. Thank you.

T77911S · 08-09-2018, 03:17 AM

what plugs did you put in.

JSZ · 08-14-2018, 03:58 AM

Sorry for the delay, my inlaws were in town....
The plugs were NGK BPR7ES

Thank you.
Jeff

HarryD · 08-14-2018, 06:43 PM

Quote:

Originally Posted by JSZ

Sorry for the delay, my inlaws were in town....
The plugs were NGK BPR7ES

Thank you.
Jeff

For my 1973.5 CIS car I have been using WR-5-DC+ (Pelican PN 999-170-165-90-M14) or NGK BP6ES (Pelican PN 7333-M220) with good success.

You plug may be too hot.

T77911S · 08-15-2018, 03:01 AM

that's a colder plug. take a look at the plug. if it is black it may be too cold, that's what I run in my 930 BTW.

JSZ · 08-15-2018, 06:38 AM

Thanks.. I did take one plug out and your right it is running cooler. Can you recommend the correct NGK plug for the heat range?

Also, my RPMs after warm up is around 1900, and can not adjust in any further. I have checked for restrictions on the throttle and cruise control, however I have not identified any. I am going to see if the condition changes by blocking off the line that feeds the AAR, AAV and decel valve.

Thanks again.

T77911S · 08-15-2018, 08:25 AM

1900-either you have a big air leak, the AAv is not closing, the DV is open or the AAR is not closing.
you said sometimes the RPMs go hi. I would look at the Dv. try disconnecting the small vac hose that goes to it and plug it.

small chance you have a distributor advance problem. you can check the timing advance with a timing light, but if you cant get the RPM down you cant check it.

you can look at the throttle body and tell if the throttle is closed completely

JSZ · 08-15-2018, 10:54 AM

Thank you.. I will get on to the AAV, DV and AAR as you have suggested. Also will remove rubber boot to inspect for and blockage of the throttle plate. The RPM issue is really a recent event within the last week and one half. I did have everything set perfectly to 950 rpms a couple of weeks ago and nothing else other then the ignition items were touched.
I will report back, can you advise on the plugs?
Thanks

JSZ · 08-19-2018, 03:01 PM

I was able this afternoon to disconnect the small vacuum hose and plug it, that is connected to the DV. It dropped the RPMs down between 600 and 1000 from 1900, however it was searching.
I have a severe hand injury, so I have not been able to get into the engine bay, as I would like.
So more time looking into the AAV, AAR and DV, hopefully I can get the idle stabilized so I can check the timing.
Any thoughts on the correct NGK plugs for a stock 3.0?
Further diagnostic help is most appreciated. Bentley, I found to be lacking.

Thank you, Jeff

JSZ · 08-29-2018, 07:33 AM

anyone?

allaircooled · allaircooled's Garage

I just checked my receipts to see what NGK plug I am running on my 2.7 and they are BPR7ES same as you. So that doesn't help you much.

T77911S · 08-30-2018, 02:41 AM

7 may be a bit cold. I would check the plugs first to see how they look. 5 may be better but its all about how they look and work. (as in do they foul)

JSZ · 08-31-2018, 05:43 AM

Thank you. I have had one plug out and noticed that the color was not correct. I will check them all and if the same get a slightly hotter plug.

Flojo · Flojo's Garage

Quote:

Originally Posted by T77911S

if you really want to make it right
remove CIS, new injector sleeves and Orings, rubber boots on runners, hoses, new injectors, new o2sensor.
if you really want to go deeper, rebuild the FD and WUR.

it will be good for another 40 years.

THIS!

renewing the seals has a much rewarding effect!
bad air is killer in this system. as well as malfunktioning components (FD, WUR..)

pmax · pmax's Garage

Quote:

Originally Posted by JSZ

anyone?

Start with the basics.

Monitor the fuel pressures to eliminate the WUR as a possible cause.

JSZ · 08-31-2018, 12:20 PM

Quote:

Originally Posted by pmax

Start with the basics.

Monitor the fuel pressures to eliminate the WUR as a possible cause.

Done that....
The car is an 82 Sc and when I purchased it, it had sat for some years with around 55K miles. I rebuilt the engine , ( with help) from the case up. O ring s were replaced to the injectors, however I was advised to leave the plastic retainer. Injectors were cleaned and then checked with a Bosch injector tool, all excellent. Rubber boots were all replaced, airbox was checked. FD and WUR were rebuilt and finally recalibrated by Tony. Warm conrtol pressure is 3.45 bars and system pressure is 4.9 bars.