Looking for advice on fast idle issue - ignition advance issue

[Ray V]

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?

 

[DFracing]

So what's the problem? 4 cyls just idle high.

 

[modelageek]

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?

maybe the PCV issue http://www.ranger-forums.com/showthread.php?t=116900

 

[modelageek]

Also the best thing to do in a situation like yours is to bring up all the maintenance. You did not say if you pulled the IACV and cleaned it out? clean the MAF, change air filter and make sure intake is not clogged, clean TB and butterfly valve.......look around for vacuum leaks ie. PCV valve.

 

[Ray V]

I will check the PCV valve. I don't have anything to lose except some time.

The vehicle is pretty well maintained. I replaced the coil myself last year. The main reason that I worked on the car was because it was leaking oil into the spark plug wells on #2 & #3 cylinders, and my friend asked me to replace the valve cover seals. While I was at it, I cleaned the MAF, IACV, throttle plate. I also installed new plugs and replaced a functional ECT sender with the wrong replacement part (that was a pain).

Thank you,