I have a 97 Nissan Quest that I recently had to do head work on. The exhaust manifold studs broke on the rear head and I had to remove head to remove the offending studs.
I replaced the studs and put the motor back together. Now I have a vacuum leak noise above 3500 rpm that increases in pitch as rpms increase.
The check engine light came on and here are the codes,
0304 - Knock Sensor
0403 - TPS
1105 - A/T third gear signal fault
1206 - TPS to A/T signal fault.
I have checked and rechecked all of the connections and have found nothing unconnected and have not been able to find this vacuum leak
I have cleared the trouble codes and they have not returned but the vacuum leak noise above 3500 remains.
What valve opens above 3500 rpm or below what ever vacuum pressure that is and is interconnected to the TPS and the trans?
I feel that it is not the Knock sensor or the TPS so it has to be a faulty vacuum operated valve.
1997 Nissan Quest 155,000