Oxygen Sensor System Help!

[tkmoore]

Guys, first I apologize for asking for help once again on diagnosing my 83 SC 3.0 warm start problem. I most recently thought i had a bad CSV or fuel pressure problem, but now, and factoring in advice you've all given me, I'm fairly certain my problem's really in the O2/lambda/frequency valve system.

PROBLEM: car starts great cold and runs fine. Once shut off warm, she re-starts fine but then won't idle unless I press gas for about 30 seconds steady. Then once she starts to maintain idle, the idle fluctuates low to normal for about 2 minuets before finally idling steady again. While I don't have access to a gauge set right now to check system pressures, I checked for vacuum leaks and found none. O2 sensor is also new and WUR was adjusted and cleaned by a good shop about 1000 miles ago. In trying to test the different CIS components as per my Bentley, I unplugged the Frequency valve and sure enough, car runs and starts fine when warm and idles nice and steady--as long as I have the FV unplugged (when plugged in, FV is buzzing as it should). I get the same Improvements in great warm starts and steady idle if I unplug the lambda cable or O2 sensor relay under the seat--all this leads me to conclude I have a fault in the FV/O2/lambda system somewhere. Also, if it helps, when i start the car i can feel the O2 sensor relay under the seat click Immediately and it stays that way until i shot the car off--not sure if this is how it should operate. At this point I'm frustrated and hoping someone here has experienced this issue and can share your thoughts. Could this be as simple as a bad O2 sensor relay? Thanks, Tim

[toddadale]

Tim:

The Bosch K-Jetronic is great though it can be buggy - sounds like the Warm-up regulator, also called the control pressure regulator, lowers the control pressure of the K-Jetronic when the engine is cold. Your car is over 30 years now - I would start there

[jason2guy]

first thing, you need to know all of the fuel pressures. just buy a set of gauges. if you plan on keeping the car its a no brainer.
cis cars w/lambda need the FV system in order to run right. you can unplug the o2 but dont unplug that relay under the ps seat. and yes it should be on all the time. your issue sounds like a fuel pressure loss after shutdown. u turn the car off, all the fuel pressure is lost and additionally the car is hot and fuel can vaporize when heated creating vapor lock, then when its restarted it has a hard time building the fuel pressure back up.
mine did the exact same thing. its either the fuel pump check valve, system pressure regulator oring, WUR, or the accumulator thats at fault, IMO

[SCadaddle]

MY 82SC had "suspect" wiring to the Frequency Valve (FV) that at some point in a previous owners life was shorted and charred/burnt, but it did work and the car was tuned to run correctly with the Lamda system functioning. Cold starts were typically on the rich side requiring some pedal action to "clear it's throat" then hunted for a minute or so then on to fast idle. Warm starts were a non-issue.
Then one day I was driving along and all of a sudden at a stop light something happened and the car started running really bad. I'm talking no power-seems to be running on 3 cylinders-park it while running and it goes waaah waaah waaah with the rear end wagging back and forth. I thought I was toast. Got it home after about a mile and shut it down. Let it cool down overnight and then gave it another go in the garage. Cold start was fantastic! Never cold started this good! Ran great to fast idle no hunting......for about a minute. Then waaah waaah waaah with the rear end wagging back and forth showed back up. Shut it down.
The fix was to rewire the FV from the wiring connector at the Lamda box to the FV and source another Lamda box as the one I had was installed in a known-well running 82SC and the symptoms followed the box. The first used box I bought stated by seller to be in working condition didn't work by the same test. Box #2 (Thanks Schumicat down in New Orleans!) passed with flying colors.
So I guess the moral of the story is that if the system is properly tuned to run on the Lamda system in closed loop mode and it goes out you WILL know it!

Also, all O2 relays are not created equal. Tony and others took me to schoolin' on that here:

911SC Frequency Valve problem

[T77911S]

i did not read past "it starts fine cold and runs fine".

i would look into pressures, check valve, residual pressure and possible ignition.

[boyt911sc]

Originally Posted by tkmoore

Guys, first I apologize for asking for help once again on diagnosing my 83 SC 3.0 warm start problem. I most recently thought i had a bad CSV or fuel pressure problem, but now, and factoring in advice you've all given me, I'm fairly certain my problem's really in the O2/lambda/frequency valve system.

PROBLEM: car starts great cold and runs fine. Once shut off warm, she re-starts fine but then won't idle unless I press gas for about 30 seconds steady. Then once she starts to maintain idle, the idle fluctuates low to normal for about 2 minuets before finally idling steady again. While I don't have access to a gauge set right now to check system pressures, I checked for vacuum leaks and found none. O2 sensor is also new and WUR was adjusted and cleaned by a good shop about 1000 miles ago. In trying to test the different CIS components as per my Bentley, I unplugged the Frequency valve and sure enough, car runs and starts fine when warm and idles nice and steady--as long as I have the FV unplugged (when plugged in, FV is buzzing as it should). I get the same Improvements in great warm starts and steady idle if I unplug the lambda cable or O2 sensor relay under the seat--all this leads me to conclude I have a fault in the FV/O2/lambda system somewhere. Also, if it helps, when i start the car i can feel the O2 sensor relay under the seat click Immediately and it stays that way until i shot the car off--not sure if this is how it should operate. At this point I'm frustrated and hoping someone here has experienced this issue and can share your thoughts. Could this be as simple as a bad O2 sensor relay? Thanks, Tim

Tim,

Without knowing your fuel pressures, you have too many critical variables to get a good grasp of your problem/s. Search for Dave Kost's posts and contact him. We have been discussing his CIS problem/s almost like yours and got an email from him today. He did all the tests and all I did was direct him how/what to test. I am sure he'll be glad to share his experience with you. And keep us posted.

Tony

[tkmoore]

Ok, it's finally figured out. After months of ignoring the great advice to start diagnosing my warm and cold start issue by testing the CIS fuel pressures (system, control, and residual) I must admit my ignorance.

First, a huge thank you to Tony D. (boyt911sc) for his great help and advice. Tony you are a huge asset to the Pelicans here. After months of throwing lots of different parts at my CIS starting issue, I was frustrated. I even had my O2 lambda unit tested at Systems Consulting (they were great too), but noting fixed the issue.

I had been reluctant to try and test the CIS myself because I had no prior experience and was afraid I would screw up the system worse. Well. Tony took the time to explain the value of doing the pressure tests and just how simple it really is. So, armed with my Bentley manual and a HF pressure gauge (with Schrader valves removed), I tried the tests and Tony was indeed correct; easy and it showed a super high control pressure indicating a faulty WUR.

Then, Tony offered to bench test my WUR and confirmed it was bad (plugged internally). He then went a step further and, for a great price, sent me a perfectly calibrated and rebuilt 090 WUR and now she runs fantastic!

Moral of my story; the experienced advice to BEGIN diagnosing CIS issues by testing the fuel pressures is the ONLY way to go. It's something most anyone can do; had I done it from the beginning in 2014, I would have saved a ton of money and she would have been running great all along.

Tony, you have been great and I owe you ONE! Thanks again,

Tim

[boyt911sc]

Originally Posted by tkmoore

Ok, it's finally figured out. After months of ignoring the great advice to start diagnosing my warm and cold start issue by testing the CIS fuel pressures (system, control, and residual) I must admit my ignorance.

First, a huge thank you to Tony D. (boyt911sc) for his great help and advice. Tony you are a huge asset to the Pelicans here. After months of throwing lots of different parts at my CIS starting issue, I was frustrated. I even had my O2 lambda unit tested at Systems Consulting (they were great too), but noting fixed the issue.

I had been reluctant to try and test the CIS myself because I had no prior experience and was afraid I would screw up the system worse. Well. Tony took the time to explain the value of doing the pressure tests and just how simple it really is. So, armed with my Bentley manual and a HF pressure gauge (with Schrader valves removed), I tried the tests and Tony was indeed correct; easy and it showed a super high control pressure indicating a faulty WUR.

Then, Tony offered to bench test my WUR and confirmed it was bad (plugged internally). He then went a step further and, for a great price, sent me a perfectly calibrated and rebuilt 090 WUR and now she runs fantastic!

Moral of my story; the experienced advice to BEGIN diagnosing CIS issues by testing the fuel pressures is the ONLY way to go. It's something most anyone can do; had I done it from the beginning in 2014, I would have saved a ton of money and she would have been running great all along.

Tony, you have been great and I owe you ONE! Thanks again,

Tim

Tim,

You are a lucky guy. If you sold your car two (2) years ago it would sell much less than today. Now that the car is running you already got a buyer and looks like it is already sold. If I knew you were were selling the car right away, I would have sent you a defective WUR. Just kidding! Kindly inform the new owner that the WUR comes with a life time warranty and transferable from owner to owner. Keep me posted. Thanks.

Tony