New SSIs in - Engine now backfires and idles rough.

[Kool-aid-82]

I double checked and tested the Frequency valve relay, on the bench,
Good.



I can feel it vibrating and I disconnected the relay with the car running and it drops RPMs. Conclusion - the Frequency Valve is working.

Once warmed up if I Connect the lambda the car drops RPM and runs bad. (Leans out to ~20.0)

Lambda disconnected runs good
AF mixture at startup is ~13.6
Warmed up it is ~14.6
Summer in houston so there is not a-lot of warmup needed.

Took some time to work on the Sunroof mechanism as well - but that is another post.

[pmax]

Interesting.

Is the O2 reading rich ?

There is a 3 pin test port near the fusebox to show what lambda the "ECU" is reading.

[Kool-aid-82]

Originally Posted by pmax

Interesting.

Is the O2 reading rich ?

There is a 3 pin test port near the fusebox to show what lambda the "ECU" is reading.

PMAX, Can you provide more info on this port?

I have manually set the Air Fuel.
It is rick at cold start but once warm hovers around 14.6

If I hook up the Lambda probe, Just below the fuel filter, the car go extremely lean +20.0

[pmax]

http://forums.pelicanparts.com/porsche-911-technical-forum/874460-help-lambda-freq-valve-test-please.html

http://forums.pelicanparts.com/porsche-911-technical-forum/821090-cis-lambda-frequency-valve-signal.html

It shows what the "ECU" is sending to the FV. Put a scope on the correct 2 wires and it shows the signal sent to the FV.

[Dave Kost]

Originally Posted by Kool-aid-82

I double checked and tested the Frequency valve relay, on the bench,
Good.



I can feel it vibrating and I disconnected the relay with the car running and it drops RPMs. Conclusion - the Frequency Valve is working.

Once warmed up if I Connect the lambda the car drops RPM and runs bad. (Leans out to ~20.0)

Lambda disconnected runs good
AF mixture at startup is ~13.6
Warmed up it is ~14.6
Summer in houston so there is not a-lot of warmup needed.

Took some time to work on the Sunroof mechanism as well - but that is another post.

Sounds like you have made good progress isolating the problem.
1.) O2 Sensor
2.) Wiring short- from O2 sensor to ECU.
3.) ECU - circuit that reads O2 sensor voltage.

Once warmed up if I Connect the lambda the car drops RPM and runs bad. (Leans out to ~20.0)

One possibility (my best guess) is that you have a shorted wire on the O2 pigtail. Could have happened when installing the SSi's, removing the O2 sensor. If the ECU reads a higher voltage (.1-.9v range), closer to .9 which is a false O2 reading, the ECU will try to lean out the mixture.

So, test the O2 sensor, (I would replace it). Also, I would buy another O2 relay, and keep the current one in the glove box as a spare.

It this doesn't solve it, start looking at sending the ECU out for testing and repair.

Let us know.

[tirwin]

Originally Posted by Kool-aid-82

PMAX, Can you provide more info on this port?

I have manually set the Air Fuel.
It is rick at cold start but once warm hovers around 14.6

If I hook up the Lambda probe, Just below the fuel filter, the car go extremely lean +20.0

This is suspect. If the lambda box is trying to lean the mixture, then it thinks the mixture is overly rich.

I'd replace the O2 sensor and carefully check the connector and wiring. Do you have an original male connector or has it been replaced? They are known to get brittle and crack.

If you fish around the fuse panel on the left side of the engine bay you will find a test port connector. It is round and has 3 pins. This is where a tech would've connected their equipment back in the day. It's usually hiding underneath the back side of the box where the heater relay is located.

[Kool-aid-82]

Wanted to thank everyone for the responses and ideas I have been traveling for work and getting my daughter married off so the car took a backseat.
But I finally got caught up and back to work troubleshooting on the car.
Everything tested kept coming back as good, but I went head and I purchased new Relays and an O3 Sensor, because they were low-cost and have extras around for testing seemed a good Idea.

The issues was easy to repeat, O2 sensor plugged in the car would run fine for ~15 mins then go to crap. (I kept thinking it was a heat sync issue.)
After testing and replacing the Fuel pump relay, ECE Relay and Coil, I finally replaced the O2 sensor and success.

Drove 200 miles of back roads around Chapple Hill and Washington TX today with my daughter. Car ran flawlessly.

Moral of this story is, start looking at what you touched last… I must have messed up the O2 sensor/wire when replacing the exhaust.

[pmax]

Congrats !!!