825 5-speek Hunting Idle (long)
03-09-2008, 01:16 AM
#1
Rennlist Member
Thread Starter
825 5-speek Hunting Idle (long)
I just finished completing a intake hose refresh. Including replacing vacuum hoses that appear to have been original. The PO disconnected the thermal valve to evap cannister and I reconnected it. The problem I have, which I didn't have before the refresh is a hunting idle. If I disconnect the advance vacuum from the distributor the idle returns to normal. Therefore I believe I have a vacuum problem.
Vacuum is as follows:
Front of throttle body (front of engine); Center port goes to vacuum advance and port on right side goes to fuel regulators and deceleration valve.
Rear of throttle body (back of engine); Center port goes to vacuum retard and the right port goes to vapor air valves.
I have also tried this configuration:
Front of throttle body (front of engine); Center port goes to vacuum advance and port on right side goes to vacuum retard .
Rear of throttle body (back of engine); Center port goes to vapor air valves and the right port goes to fuel regulators and deceleration valve.
Did I miss a configuration? I have swapped the advance and retard vacuum lines in each of the above situations.
I've done several searches, which gave me the above configurations... any thoughts on the problem? Again it is a US 4.5 liter, L-Jet, 5-speed.
Vacuum is as follows:
Front of throttle body (front of engine); Center port goes to vacuum advance and port on right side goes to fuel regulators and deceleration valve.
Rear of throttle body (back of engine); Center port goes to vacuum retard and the right port goes to vapor air valves.
I have also tried this configuration:
Front of throttle body (front of engine); Center port goes to vacuum advance and port on right side goes to vacuum retard .
Rear of throttle body (back of engine); Center port goes to vapor air valves and the right port goes to fuel regulators and deceleration valve.
Did I miss a configuration? I have swapped the advance and retard vacuum lines in each of the above situations.
I've done several searches, which gave me the above configurations... any thoughts on the problem? Again it is a US 4.5 liter, L-Jet, 5-speed.
05-21-2008, 01:47 AM
#2
Rennlist Member
Thread Starter
just updating the post. Resolution was to disconnect the decel valve
Not taking credit for below just making it easier incase someone does a search. Not sure where I found it but it helped.
A rythmic idle up and down might be a tired vacuum limiter (UFO shaped thing on the side of the throttle body.) It can be replaced with a 5/8" and 3/4" rubber heater hose blockoff plugs with no ill effect.
I then pulled out the might vac and tested the decel valve. The WSM claims that if you add vacuum, the idle should rise. This indeed happened after I added a number of pumps, however then it went into the idle oscillation that I had seen before.
Not taking credit for below just making it easier incase someone does a search. Not sure where I found it but it helped.
A rythmic idle up and down might be a tired vacuum limiter (UFO shaped thing on the side of the throttle body.) It can be replaced with a 5/8" and 3/4" rubber heater hose blockoff plugs with no ill effect.
I then pulled out the might vac and tested the decel valve. The WSM claims that if you add vacuum, the idle should rise. This indeed happened after I added a number of pumps, however then it went into the idle oscillation that I had seen before.
