1989 244 running rich and surging idle

[Trevor57]

The car is throwing a 113 code "Fuel trim (lambda control)too lean or rich" At idle it goes from normal to about 1500 rpms or so, and then back down. The cycle takes about 3 seconds. When I pulled the spark plugs, all of them were black. I replaced o2 sensor, maf, iac, tps, checked for vacuum leaks and no changes. I bought this car with problems, so I am starting from a position of uncertainty. I checked ect resistance at the ecu, and it was 1500, which seemed correct. I have also adjusted the throttle body linkage, and tps and believe them to be correct. Any ideas on where to go from here are welcome.

 

[dl242gt]

Make sure to test the resistance of the coolant temp sensor at three stages. Cold engine should be the highest resistance. Then a warm engine, and you should see the resistance go down to say 600-800ohms. Then fully warmed up it should be at around 250-300 ohms.

 

[hiperfauto]

Have you checked the fuel pressure regulator? A bad diaphragm will leak fuel into the intake manifold via the vacuum hose. Also, a stuck regulator will give full pump pressure to the injectors.

 

[Trevor57]

I also replaced the fpr.

 

[Trevor57]

I went out and re adjusted the tps, and the idle is no longer surging. It is a little higher than I think it should be, but I do not have a tach installed yet, so I will consider the matter solved for the time being. It is driveable, so I will put some miles on it, and see what it's like in a few days. Thanks for the suggestions.

 

[djackson1993volvo940]

The car is throwing a 113 code "Fuel trim (lambda control)too lean or rich" At idle it goes from normal to about 1500 rpms or so, and then back down. The cycle takes about 3 seconds. When I pulled the spark plugs, all of them were black. I replaced o2 sensor, maf, iac, tps, checked for vacuum leaks and no changes. I bought this car with problems, so I am starting from a position of uncertainty. I checked ect resistance at the ecu, and it was 1500, which seemed correct. I have also adjusted the throttle body linkage, and tps and believe them to be correct. Any ideas on where to go from here are welcome.

I'am having the same problem? My 940 has a rough idle, it shift in 3rd at about 3500 rpms. Then it will idle normal, I'm changing spark plugs, wires, and injectors. I hope that will bring down the rough idle?