1996 5.0l idle rpm and timing

[Taube]

So my engine seems to idle like crap. I put my live stream data logger on it and noticed it idle s at 650 rpms and the spark advance was at 22-24 degrees. Seems very high to me. So I slowly rev the engine to 724rpms and the spark advance drops to 15-17 then rises from there as I rev it up. So big question is should I raise rpm to 724rpms. Also why would the computer be adding so much timing at low rpm s. Thanks for any tips advice and knowledge. Love this forum..... ps 1996 5.0

 

[1998Exp]

So my engine seems to idle like crap. I put my live stream data logger on it and noticed it idle s at 650 rpms and the spark advance was at 22-24 degrees. Seems very high to me. So I slowly rev the engine to 724rpms and the spark advance drops to 15-17 then rises from there as I rev it up. So big question is should I raise rpm to 724rpms. Also why would the computer be adding so much timing at low rpm s. Thanks for any tips advice and knowledge. Love this forum..... ps 1996 5.0

Idle speed is not adjustable - the PCM (computer) sets it where it "thinks" it should be, given the coolant temperature, a/c on or off, etc. And what does "like crap" mean? Any codes?

 

[Taube]

Idle speed is not adjustable - the PCM (computer) sets it where it "thinks" it should be, given the coolant temperature, a/c on or off, etc. And what does "like crap" mean? Any codes?

It keeps stumbling like a miss fire

 

[1998Exp]

If you don't see any codes, the most common reason for unstable idle is a malfunctioning IAC (idle air control). You can try cleaning it, though it may be only a temporary fix. Search this forum for advice on how to do that.

 

[Taube]

It keeps stumbling like a miss fire

Also no codes

If you don't see any codes, the most common reason for unstable idle is a malfunctioning IAC (idle air control). You can try cleaning it, though it may be only a temporary fix. Search this forum for advice on how to do that.

Ok I ll try that first

 

[CDW6212R]

Ditto, clean the IAC gently, and never adjust the "idle" screws. Those are set for the PCM and altering them messes up the idle control of the computer.

Take the IAC off, hold it with the motor/solenoid up always, and gently spray the passages. You are aiming to clean only the seat where the plunger rests as it closes off the passage. So you want to gently open that(push the plunger away from the seat area, and clean the surfaces of the seat and plunger. That gets fouled in there and can stick or not flow the proper air due to the build up there. The OEM IAC's can last forever if they are clean.

 

[XploderPhil]

You also need to check and adjust the throttle stop screw to spec.
If it's not correct you may continue to have idle problems.
Never use this screw to adjust idle speed, that is the job of the ECM using the IAC, Timing, Etc

 

[Taube]

Ditto, clean the IAC gently, and never adjust the "idle" screws. Those are set for the PCM and altering them messes up the idle control of the computer.

Take the IAC off, hold it with the motor/solenoid up always, and gently spray the passages. You are aiming to clean only the seat where the plunger rests as it closes off the passage. So you want to gently open that(push the plunger away from the seat area, and clean the surfaces of the seat and plunger. That gets fouled in there and can stick or not flow the proper air due to the build up there. The OEM IAC's can last forever if they are clean.

Ok thanks

You also need to check and adjust the throttle stop screw to spec.
If it's not correct you may continue to have idle problems.
Never use this screw to adjust idle speed, that is the job of the ECM using the IAC, Timing, Etc

Well I cleaned it out rpms a bit higher but still has this stumble. New plugs wires and different coil packs still here

 

[CDW6212R]

If you adjusted the idle screw, I hope that you did not, that will require correcting. It is not a simple thing to correct that, there is a special procedure to set the idle screw. I don't know the procedure, I have never adjusted any idle screw of the dozen or so EFI Fords I have owned. I have read it posted rarely, but it's not easy to remember.

So if you have to fix the idle screw, get to hunting for the setting procedure, that will be necessary to get the idle set right with the PCM and IAC working together.

The idle screw has nothing to do with the stumble, or any other issue, or the idle itself. The computer has complete control of the idle, don't try to force a change around it. The idle is set in the computer tune.

 

[Taube]

If you adjusted the idle screw, I hope that you did not, that will require correcting. It is not a simple thing to correct that, there is a special procedure to set the idle screw. I don't know the procedure, I have never adjusted any idle screw of the dozen or so EFI Fords I have owned. I have read it posted rarely, but it's not easy to remember.

So if you have to fix the idle screw, get to hunting for the setting procedure, that will be necessary to get the idle set right with the PCM and IAC working together.

The idle screw has nothing to do with the stumble, or any other issue, or the idle itself. The computer has complete control of the idle, don't try to force a change around it. The idle is set in the computer tune.

No I never touched it.

 

[1998Exp]

How old are your plug wires?

 

[Taube]

How old are your plug wires?

Two weeks old bin chasing this issue for 3weeks now

 

[EB4X]

Cleaning it (IAC) doesn't always correct......sometimes it needs replacing.... $25 - $30 on ebay...
You might want to carefully spray the MAF element with MAF/ or electronics cleaner too ...just to cover that possibility as well.. (especially if you use a high flow oiled filter / K&N)

 

[Taube]

Cleaning it (IAC) doesn't always correct......sometimes it needs replacing.... $25 - $30 on ebay...
You might want to carefully spray the MAF element with MAF/ or electronics cleaner too ...just to cover that possibility as well.. (especially if you use a high flow oiled filter / K&N)

Ok thanks

 

[CDW6212R]

No I never touched it.

Very good. Then clean the IAC and see how it runs. Did it have a miss before the plugs and wires? Sometimes a new plug can be bad to start with.

Have the coil packs been disconnected lately? All of the wires are old now, slight wire connection issues pop up more now. Gently look at the coil pack connectors and reconnect them. I had a loose connection at one of mine about two months ago, the engine ran very rough, and playing with those two fixed it immediately(I have a suspect connection there now of course).

 

[Taube]

Ok thanks

What is fuel pressure on these ?

Very good. Then clean the IAC and see how it runs. Did it have a miss before the plugs and wires? Sometimes a new plug can be bad to start with.

Have the coil packs been disconnected lately? All of the wires are old now, slight wire connection issues pop up more now. Gently look at the coil pack connectors and reconnect them. I had a loose connection at one of mine about two months ago, the engine ran very rough, and playing with those two fixed it immediately(I have a suspect connection there now of course).

Yes had the stumble/Miss before plugs and wires. I checked fuel pressure is 32 psi and hits about 40 with vacuum regulator disconnected.

 

[CDW6212R]

Those are good psi numbers. The IAC should affect idle rpm but now create a miss. So go at it expecting it to be a spark issue, bad coils, plugs or wires, or wiring.

 

[Taube]

Those are good psi numbers. The IAC should affect idle rpm but now create a miss. So go at it expecting it to be a spark issue, bad coils, plugs or wires, or wiring.

So far new plugs and wires coils I swapped out from my other truck still stumble s like a miss at idle ???

 

[Joe Dietz]

So far new plugs and wires coils I swapped out from my other truck still stumble s like a miss at idle ???

Swap the coils, gonna bet its the coils ;-)

 

[CDW6212R]

Yeah, try the coils again, and first gently play with the coil pack wires and connectors. Any slight wiring issue will cause a miss or stumble. As these get older more of the miss issues will be wiring, be gentle with old stuff.