neuroptic

My 85 4 KS is giving me troubles. It idles a little rough but at about 1250 rpms constant until I hit the throttle. It then starts to surge between almost stalling and back to about 1250 rpms. It will do this forever. I have replaced the plugs,cap and rotor. I replaced the idle speed valve, the thermo time switch, have checked the cold start injector and for vacuum leaks. I have checked the coolant temp with a temp gauge and its right around 185 deg, the fans come on alright and everything. While checking the O2 sensor I didn't notice any diffrence when I unplugged it. Does it have to be plugged into check it? I read the Bentley book but it is kind of confusing. Anyone checked there O2 sensor before, and can give some in-site? The only thing I haven't checked is the CO level as I don't have a gauge for that. Hopefully somebody will know what it may be as I am getting frustrated!!


Jim

neuroptic

Anyone know of any web sites that might be able to help me with this?

Kidquattro

...some say (Blaufurnugen's website speaks of this) that the O2 sensor is bad. But in your case it sounds like it does it anyway with it unplugged. I had a similar problem the past winter in my 5kqt. They pulled the codes and teaked a little here and tourqued alittle there and blamo, runs awesome. Unfortunetly I couldn't tell you what they did because the kid who fixed it doesn't work there any more. I'm guess that a sensor or valve is not doing it's job correctly or failed. Vacuum is another issue as well. May check for that. I wish I could be of more help but i bet someone from the list can help.

mt6127

There are a few more things to check out... Are there any other driveability issues?? The Bentley has a diagnostic matrix on the FI to follow. I've been tracing some similar issues and here's a few other things that may contribute to a coarse idle or stalling:
1) Fuel Pressure - weak pump flow or a failing differential pressure regulator (little box on the front of the fuel distributor)
2) crankcase tube into the ISV should be checked and cleaned if clogged
3) dirty injectors or leaky o rings
4) dirt in fuel distributor
4) sticky airflow plate
5) engine timing
6) wiring (I had 1 y/o wires and found arcing off the coil wire - tip: assume nothing - spritz the wires with a mist of water then start the car in the dark to see if you can see or hear any arcs, plug off vacuum lines to isolate possible leaks)
7) use Google to search on K-Jetronic. VWs and Volvos used the same FI and you can find similar tips and issues. Good luck, w/o the pressure guages and the electrical test gear, you may need to start swapping out parts (ie buy a used fuel distributor, CSV etc)

neuroptic

I changed out the O2 sensor and it acts exactley the same as before.

Jim