82 911SC Running Issues

[mike621]

Originally Posted by boyt911sc

Mike,

The video of the warm up is of no value because you were helping the engine by pressing the gas pedal. What I like to see and watch is how the cold engine performs during its warm up stage.

Repeat the test and put the car in neutral and hand brake on. Open the driver side window and reach for the ignition switch. Do not get inside the car. Start the motor and video the start up. I like to see the cold engine RPM for the initial 3 mins. unassisted. Meaning you stay out of the car and let the engine run unassisted.

If you install a CIS pressure gauge during the test, you will have an idea how the cold control pressure transition to warm control pressure in a couple of mins. or less. If your engine will not idle without further assistance, you got a big problem. Thanks.

Tony

Tony, I appreciate your enthusiasm but see no difference in why a small press of the accel at 5 mins in makes a big difference in the conversation here. IIRC car is idling unassisted for at least a few mins in the video.

I'll see if I can get you another clip of it idling before I send the CDI out to our hosts for a check and rebuild.

Aware there are multiple issues in play and I'm hopeful with the improvement of cold idle at this point. Will be pulling injectors in a future test. I know the FD will also need work due to the low residual pressure at the unit causing an intermittent hard warm start.

[mike621]

Originally Posted by boyt911sc

Mike,

If you want to find out the culprit of your cold idle problem, take a short video after sitting over night. Show how the engine does its warm up cycle for the first 3 mins. Attach the pressure gauge and monitor the control pressures versus time. Based from the information in post #1, the engine will experience a cold erratic idle specially at this time of the year when it is colder.

Once the engine has warmed up, everything would be normal. And that’s what your video showed up. Thanks.

Tony

Here's 10 mins of starting from cold, gauges on, until the idle fully settles down.

[Dave Kost]

Mike,

I think you need to set the mixture before doing anything else. Here is a link to setting the mixture without any special tools.

https://www.youtube.com/watch?v=8TcAzqKxWgY

Pay attention to the way he sets the mixture- not the stuck plunger.

[Dave Kost]

Originally Posted by Dave Kost

Mike,

I think you need to set the mixture before doing anything else. Here is a link to setting the mixture without any special tools.

https://www.youtube.com/watch?v=8TcAzqKxWgY

Pay attention to the way he sets the mixture- not the stuck plunger.

Since you have a Lambda car, you need to disconnect the O2 sensor for the initial mixture setting.

[icarp]

Originally Posted by Dave Kost

Mike,

I think you need to set the mixture before doing anything else. Here is a link to setting the mixture without any special tools.

https://www.youtube.com/watch?v=8TcAzqKxWgY

Pay attention to the way he sets the mixture- not the stuck plunger.

I do not like this video, never grip the fuel plunger with pliers.
When he turns the CO adjustment screw he moves it WAY too much , the screw is very sensitive and makes large changes for small adjustments . Turn the screw with reference to minutes not hours , rich in , lean out , idle at 925 , make sure ignish timing is set to spec . mix is correct when surging is gone and no rpm bounce after a rev up.
Just my thoughts .
PS Tony is the master , do what he says and you will be successful.
HAPPY THANKSGIVING

[Dave Kost]

Originally Posted by Dave Kost

Since you have a Lambda car, you need to disconnect the O2 sensor for the initial mixture setting.

From another post (not me).

"I found that every CIS engine has its particular 'happy place' where it likes to run. No two are exactly the same but CO% usually falls between 2-3.5%.

This can be set by ear and its very acurate for best performance. If tuning CIS w/ lambda, disconnect the O2 sensor first.

The trick to find your engines happy CO is to get the engine at least running and with the airbox cover and filter off, SLIGHTLY lift the air sensor plate via the exposed elbow with a finger, knuckle or whatever. All is needed is very slight pressure to notice any change in RPM. If the engine RPM increases it wants to be richened. This is also true if you were to pull down on the sensor plate. If RPM's increase, then it wants to be leaned out. Make very small adjustments with the 3mm allen as necessary. The trick is to get the engine at a max RPM so when you either push or pull on the sensor plate, the RPM's will drop (from either being too lean or rich)."
______________

[mike621]

Quick update here:

Adjusted mixture with o2 disconnected, appeared to be running ok until reconnecting. I also had an epiphany, realizing while I was debugging and running around, I was doing so with the heater duct disconnected. This was introducing more heat into my engine bay. Car is running a little cooler now. I expect that once I replace the inop heater blower fan, this will improve further. Haven't gotten the car hot enough to stall it on the highway lately.

One last thing that may have related to my "CDI problem": cleaned up several electrical connections under/around the rear fuse box. I'll post results once i have the new blower fan in place, but I still think the CDI may benefit from a refresh. We'll see.

[Dave Kost]

Originally Posted by mike621

Quick update here:

Adjusted mixture with o2 disconnected, appeared to be running ok until reconnecting. I also had an epiphany, realizing while I was debugging and running around, I was doing so with the heater duct disconnected. This was introducing more heat into my engine bay. Car is running a little cooler now. I expect that once I replace the inop heater blower fan, this will improve further. Haven't gotten the car hot enough to stall it on the highway lately.

One last thing that may have related to my "CDI problem": cleaned up several electrical connections under/around the rear fuse box. I'll post results once i have the new blower fan in place, but I still think the CDI may benefit from a refresh. We'll see.

Nice work!

[mike621]

Wrapping this up for now.

Cold start fixed by cleaning the harness connection on the shock tower area. Corrosion was causing the FV to be inop or intermittent.

Prior to this thread, my car got new plugs, wires, cap and rotor and battery ground.

Highway stall condition seemed related to excessive engine compartment temps. Mitigated this by:
1. Cleaning out the mouse nests in the fan shroud.
2. I was driving around troubleshooting with my heater pipe sending super hot air into the engine bay (blower was off). Replaced the bad heater pipe, inop blower motor, and cleaned up connections at the rear fuse box that were corroded.
3. Fixed a loose connection on the sensor on the right timing cover.
4. Coil resistance was out of spec, replaced with MSD HV 8222

The car has since not gotten hot enough for the ignition drop /highway stall to happen. If this behavior resurfaces in warmer weather, I will send the CDI unit for rebuild with Pelican.

I plan to address the low residual pressure/hot start by replacing the pressure valve o rings at the CIS, since tests showed the issue was not in the WUR part of the circuit. Will test again before those parts are bought.

I still need to fine tune the mixture more and will reach out to a local pelican for help once this pandemic subsides some.

Thanks again everyone here for help. Took the car out on a few joyrides and I'm feeling good.

[Dave Kost]

Mike That's great news. Glad it was something stupid and (cheap) like corroded wires.

Thanks for reporting back.

[997at]

Originally Posted by mike621

Wrapping this up for now.

Cold start fixed by cleaning the harness connection on the shock tower area. Corrosion was causing the FV to be inop or intermittent.

Prior to this thread, my car got new plugs, wires, cap and rotor and battery ground.

Highway stall condition seemed related to excessive engine compartment temps. Mitigated this by:
1. Cleaning out the mouse nests in the fan shroud.
2. I was driving around troubleshooting with my heater pipe sending super hot air into the engine bay (blower was off). Replaced the bad heater pipe, inop blower motor, and cleaned up connections at the rear fuse box that were corroded.
3. Fixed a loose connection on the sensor on the right timing cover.
4. Coil resistance was out of spec, replaced with MSD HV 8222

The car has since not gotten hot enough for the ignition drop /highway stall to happen. If this behavior resurfaces in warmer weather, I will send the CDI unit for rebuild with Pelican.

I plan to address the low residual pressure/hot start by replacing the pressure valve o rings at the CIS, since tests showed the issue was not in the WUR part of the circuit. Will test again before those parts are bought.

I still need to fine tune the mixture more and will reach out to a local pelican for help once this pandemic subsides some.

Thanks again everyone here for help. Took the car out on a few joyrides and I'm feeling good.

Glad to see progress Mike. Just ping me when you’re ready to set the mixture.

[mike621]

Revisiting this thread. A lot has happened since the end of 2020.

Fixing the electrical connections got the car running well enough to drive on weekends and fun highway jaunts.

I continued to experience overheating issues and random stalls, but less frequent. CIS testing got me to change the fuel accumulator too. Much improved. Eventually, the oil leaks became so severe that I was unable to drive the car safely any longer. I did have the CDI rebuilt by Pelican but my stalling issues remained.

I (mostly) parked the 911 in the summer of 2021 and pulled the engine out two months ago.

Contributing to my running issues I found:

• 'Green wire' burnt, exposed (to be replaced with 928 style wire)
• Mud, acorns, and mouse debris caked in cylinder fins on all cylinders, inhibiting cooling
• vacuum leaks on molded metal/rubber hoses
• under-torqued valve covers and sump plate cover (my fault after trying my first service)

I'm replacing all vacuum hoses, fuel lines, chain tensioners (Carrera), drain tubes, triangle of death, CIS hoses, fuel dist rebuild, injectors, front and rear crank seals, and topping it off with a new clutch mating to the rebuilt 915 transmission. Had the oil tank and cooler cleaned and refurbed at Pacific cooler.

Oh and some new pedal bushings and shocks as these were way worn...

[boyt911sc]

Mike,

Have you done anything to the WUR? The problem would not be noticeable with the heat wave going on now, but once the weather gets cooler in the fall an erratic cold idle problem would appear.

Item #5 (Post #1): Says that the WUR heater resistance with the engine cold was 9.5 Ohms. This was a clear indication that the WUR needed some work.

Tony