Welcome Visitor! Please take a few seconds and Ray V
New Member
- Joined
- Dec 9, 2010
- Messages
- 6
- Reaction score
- 0
- Points
- 0
- Vehicle Year
- 2003
- Make / Model
- Mazda
- Transmission
- Manual
Hello, I am looking for advice on repairing a friend's 2003 B2300. The engine is not idling properly. When the throttle is let off, the engine idle does not drop smoothly down to 800-900 rpm. The idle drops to at around 1300, stays there for a few seconds, and then falls to around 900 rpm. There are no codes. I use an Actron 9580A scanner (not professional grade).
I suspected a bad temperature sending unit (either ECT or CHT) or perhaps a malfunctioning IACV, but they tested OK. The O2 sensors test OK (and the problem is unchanged with the O2 sensors unplugged). I expected the ecu to throw a code with the O2 sensors unplugged but there was none.
The EGR valve is a pain to access so I have not touched it.
I think that the problem lies with my ignition advance. The ignition advance, under constant engine rpm with no load, is as follows:
900 rpm - 0 degrees
1500 - 10
2000 - 10
2500 - 15
3000 - 20
When I blip the throttle quickly, the rpm rises to around 1300 rpm, stays there for a few seconds, and then falls back to 900. The ignition advance is as follows: 0 at idle, a sudden drop to around -8 degrees and then a fairly rapid rise to about 15 degrees. The advance stays high for a few seconds until the suddenly dropping to around -6 degrees. The engine rpm falls at exactly the same time that the advance drops. This vehicle has no distributor, so I am unsure how to test the vehicle further to determine if the ecu is bad or something else.
Any suggestions?
I suspected a bad temperature sending unit (either ECT or CHT) or perhaps a malfunctioning IACV, but they tested OK. The O2 sensors test OK (and the problem is unchanged with the O2 sensors unplugged). I expected the ecu to throw a code with the O2 sensors unplugged but there was none.
The EGR valve is a pain to access so I have not touched it.
I think that the problem lies with my ignition advance. The ignition advance, under constant engine rpm with no load, is as follows:
900 rpm - 0 degrees
1500 - 10
2000 - 10
2500 - 15
3000 - 20
When I blip the throttle quickly, the rpm rises to around 1300 rpm, stays there for a few seconds, and then falls back to 900. The ignition advance is as follows: 0 at idle, a sudden drop to around -8 degrees and then a fairly rapid rise to about 15 degrees. The advance stays high for a few seconds until the suddenly dropping to around -6 degrees. The engine rpm falls at exactly the same time that the advance drops. This vehicle has no distributor, so I am unsure how to test the vehicle further to determine if the ecu is bad or something else.
Any suggestions?
