911 SC 1983 warm running issue

[Hyllski]

WCP with vacuum (engine running) is 50 psi.

Drove the var again today and it is still not quit good. I assume I have another issue as well maybe? Fuel pressures should be OK now...

Steinar

[pmax]

089 chart's here.

CIS Troubleshooting for Dummies

[boyt911sc]

Originally Posted by Hyllski

WCP with vacuum (engine running) is 50 psi.

Drove the var again today and it is still not quit good. I assume I have another issue as well maybe? Fuel pressures should be OK now...

Steinar

Steinar,

You need to adjust the WCP with vacuum. But leave it alone this time and focus your troubleshooting for unmetered air. The WCP is within spec. Have you checked your ignition timing and valve adjustments lately? How old are your spark plugs?

Use a smoke generator to locate these hard to find air leak source/s. It is more efficient than using starter fluid or carb cleaner for finding the culprits. Keep us posted.

Tony

[Hyllski]

Spark plugs, cables and coil are brand new.
Adjusted valves 3 years ago, driven maybe 8-10 000 km since then.

I will try to check the ignition timing and start looking for a smoke generator.

Steinar

[Hyllski]

A little update on my project:

Got myself a smoke machine. Tried it with engine running and the smokehose pointing at every possible place there could be leaks in the engine room. No result. Tried to stop the engine and filled the complete air system with smoke. Blinded off air intake. Forced open air dampers to get smoke all the way into the sylinders. Found one small leak and fixed it. No difference in engine performance. So false air is then off the list.

Went to my old workplace and borrowed the exhaust emission tester.
Results:
CO: 1,55%
CO2: 14%
O2: 0,25%
HC: 133ppm
Nox: 0ppm
Lambda: 0,96

I think this is normal numbers?

Next up now is checking ignition timing...

[boyt911sc]

Originally Posted by Hyllski

A little update on my project:

Got myself a smoke machine. Tried it with engine running and the smokehose pointing at every possible place there could be leaks in the engine room. No result. Tried to stop the engine and filled the complete air system with smoke. Blinded off air intake. Forced open air dampers to get smoke all the way into the sylinders. Found one small leak and fixed it. No difference in engine performance. So false air is then off the list.

Went to my old workplace and borrowed the exhaust emission tester.
Results:
CO: 1,55%
CO2: 14%
O2: 0,25%
HC: 133ppm
Nox: 0ppm
Lambda: 0,96

I think this is normal numbers?

Next up now is checking ignition timing...

Hyllski,

Please share with us your smoke test set-up. How could you perform a smoke test with the motor running? Something I like to learn from you. You need to isolate the system (engine) from atmospheric pressure to locate these hard to find leak source/s. Thanks.

Tony

[Hyllski]

The smoke test with engine running was not a big success. The smoke generator has a 6 mm hose that I pointed at all possible places I assume there could be leaks and expecting smoke to be drawn into the engine if any leaks. However this is not very easy to see I think.

Thats why I quickly went over to do a test with engine off. Removed airfilter and taped airfilterbox with plastic. Locked both dampers in air system open. Removed a plug on airfilterbox and made a connection for smoke generator. This worked pretty good and as I mentioned before I found a small airleak with this setup. This is now fixed, but engine is still not perfect.

Is it a better way to do this? Please let me know as I really want to get the car fixed and perfect.

Steinar

[Hyllski]

Checked the ignition timing today:

Removed vacuumhose on distrubitor. 4000 rpm´s and spot on at the 25 degree BTDC mark on the pulley wheel. Connected vacuum hose and got another 3 degrees. My workshop manual do not describe any other test than this but I noticed that the ignition was set to 2-3 degrees after top dead center when car idled on 1000 rpm. Is this normal?

I noticed that the light from the ignition timing lamp (which is brand new) was a bit uneven on the blinking frequency. Could this be an issue? Is it possible that the coil dont deliver all the sparks its supposed to? Coil, cables and plugs are brand new. Tips on this?

Steinar

[Hyllski]

Checked injectors yesterday. Simply pulled them out and stuck them in 6 small bottles.

No leaks
Good spray on all 6
Same amount of fuel in all bottles.

One more thing that seems fine.

Whats next?

[boyt911sc]

Originally Posted by Hyllski

Checked injectors yesterday. Simply pulled them out and stuck them in 6 small bottles.

No leaks
Good spray on all 6
Same amount of fuel in all bottles.

One more thing that seems fine.

Whats next?

Hyllski,

That is good news. The injector/s spray patterns should be atomized in a V-shape spray pattern. No jet or stream-like fuel flow. People have commonly mistaken or misunderstood how a good fuel spray should look like during injection.

Tony

[Hyllski]

Originally Posted by boyt911sc

Hyllski,

That is good news. The injector/s spray patterns should be atomized in a V-shape spray pattern. No jet or stream-like fuel flow. People have commonly mistaken or misunderstood how a good fuel spray should look like during injection.

Tony

Tony:

Could a wrong spray pattern be enough to make the car surge? The V-shape did not appear before I pressed the air-damper real high. More of a straight down stream with low load.

Steinar

[boyt911sc]

Hyllski,

I am curious to see your ignition coil. A picture would be great. Have you tested it before? Thanks.

Tony

[Hyllski]

Originally Posted by boyt911sc

Hyllski,

I am curious to see your ignition coil. A picture would be great. Have you tested it before? Thanks.

Tony

I have changed the coil. Old one Bosch, new one Beru

[boyt911sc]

Hyllski,

At first glanced, I thought you had the silver colored ignition coil Made in Brazil . The Beru coil you got has the “Germany” on it and should not be a concern.Thanks.

Tony

[Hyllski]

PROBLEM SOLVED!

So today I think I dare to conclude that I finally have found the issue on my car. I had plans on changing the electric rotor on the car since it had a rotor with rev limiter (excuse my english! Google translate from norwegian...) on. I really dont like when the rev limiter kicks in and I´ve been wanting to put in a simple rotor without this future. I put this project on hold as the car started to surge last summer. I quickly put the rotor and the distributor lid on the OK list as they where not that old.
Anyways, last week I bought a new rotor and installed it. I instantly had a good feeling when I drove the car for a test drive. It worked really well. I have driven it every day for a week now with no sign of surging. Today I put the old rotor on and the trouble was back. Put the new rotor on again and the car is fine...

Thank you for all your help! Especially you Tony! I have learned a lot!

Best regards Steinar