1995 3800 Trans Sport Rough idle

Today, suddenly my Trans Sport is idle rough. The rpm is fluctuating from 600 to 900 rpm with the frequency of about 1-2 seconds. There is no problem driving the car. It is the running well and the TCC applies in both 3th and 4th gear. I have checked for vacuum leaks but not find any. I have tryed to disconnect the EGR connector, no improvment, and I have also checked that the pintle is not stucked. I did find three DTCs:

P0131 HO2S low signal voltage
P1406 EGR -valve pintle position error
P0171 Fuel trim lean

At idle the fuel trim is lean all the time. At driving the car the fuel trim goes from lean to rich with a frequency of about 5-10 s.

What is wrong? Vacuum leak? Bad MAF sensor? Could it be a exhaust leak?

All help is appreciated!

Check your Maf sensor....make sure it's clean...also make sure the connector makes good contact....also the 3 wires that lead to it....with ignition on..motor off..check to see that you have voltage and that the ground is good...as you check the voltage wiggle around the wires see if it loses any power.


THere is a big black connector on the tire well on the left(facing the motor) the 3 wires from the MAF go there..you could aslo do a continuity test by unpugging that connector and find those 3 wires....


r.

Thanks for the reply,
I did clean the MAF. It was dirty, but cleaning it didn´t make any improvement. Ithen checked the EGR once more and find the problem. I year ago, when I changed the EGR-valve I didn´t have a new gasket, so I made one out of gasket material. The gasket didn´t stand the heat and was almost gone by now, and air could pass in....