Slight misfire at idle

[Ecomike]

Check these out, possibly the distributor sensor, or wiring there, or bad bearing in the dizzy?

http://www.autocodes.com/p0320_ford.html

Possible causes
- Faulty Ignition/Distributor engine speed sensor
- Faulty Crankshaft Position sensor
- Ignition/Distributor engine speed sensor harness is open or shorted
- Ignition/Distributor engine speed sensor circuit poor electrical connection
- Low battery charge
- Faulty Engine Control Module (ECM)
What does this mean?

When is the code detected?
The P0320 code is triggered when the Engine Control Module (ECM) detects that there is no current at the ignition coil group
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/Loss of Power
- The engine may be harder to start
- The engine may stumble or stall
P0320 Ford Description
Ignition failure sensor is used to check whether the spark ignition is occurred correctly or not and also used to tachometer drive. The sensor monitors the voltage difference between a resistance which is on the battery circuit for ignition coil. When the ignition coil works properly, the electric current through the resistance is detected as voltage drop. This is confirmed for every ignition event with the crankshaft sensor and the camshaft sensor. If Engine Control Module (ECM) detects a malfunction, no ignition is possible, so the engine would not start. If there is no ignition signal for a predetermined cycle for one or two ignition coils, an ignition coil circuit failure exists.

Read more: http://www.autocodes.com/p0320_ford.html#ixzz49DRw2uAW
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[Ecomike]

Here is an even better more complete write up on the 320 code

https://www.yourmechanic.com/articl...ed-input-circuit-malfunction-by-jamahl-walker

 

[Ecomike]

Hard to tell if the P0320 code for jeep is only the CPS sensor or if it could also, and /or be camshaft sensor (distributor)???

The P1694 code seems totaly unrelated unless wire harness damage is in the same area the wires join up to go to the ECU for the 320 and ?

[FONT=Arial,Helvetica]P1694 is "No J1850 messages received from the powertrain control module-Aisin transmission."[/FONT] to the PCM

Does the AW4 wiring get routed with CPS/ dizzy wiring at some common wire damage point on the OBD-II jeeps? I am assuming this an automatic transmission rig? You never gave us the specs, year.

Did you disconnect any main connectors recently.

 

[old_man]

Are you still getting the cylinder specific misfire code, and if so, is it still the same cylinder?

 

[Petemech]

Vehicle specs: 1998 Cherokee (base model I believe), 4.0l automagic, np232 transfer case. This is what I've done or I've confirmed has been done by PO so far.

Ford 4 hole injectors with new o-rings

Plugs, cap, rotor, wires.

Oil change

New ground strap from cylinder head to firewall

Cleaned all other ground connections that I know of

Checked wiring from PCM to injector #1, CPS, distributor. Using a multimeter I verified there was no opens, high resistance, shorts to ground or pin-to-pin shorts all all circuits going to those three components.

Verified no corrosion in pcm, injector #1, CPS, or distributor connectors.

Swapped injector 1 and 2 P0301 finally returned this weekend confirming its not an injector.


I've noticed some times when making pressing the accelerator down slightly, like when your climbing a hill it doesn't respond but then I'll let off and press down significantly more it will take off like it should. Also is intemitant. Some times the engine is so smooth you could balance a quarter on the valve cover other times its really rough. But only at idel or low rpm. When your on the highway cruising it seems fine. And I just went to my parents this weekend 2 hours each way and calculated my fuel economy and it was about 20mpg. I'm really confused as to what's going on. If I had the extra cash this week I'd probably just load up the parts canon and fire away but I'd rather not.

 

[Petemech]

Just read through your posts Ecomike. Good stuff there. I'm gonna tear back into her this week. I'm really feeling like that bad bearing in the distributor could be a winner. Could explain why it seems to go away at higher rpm.

 

[Ecomike]

Dizzy distributor problem would show up as oil leaking into the rotor cap area and/or physical damage to the cap pins and rotor tip from physical contact. Eveb a new cap or rotor can be bad, shorting or arcing through cracked plastic.

You could have a bad plug wire or spark plug. Try a new plug, or swap plugs next now that fuel injector test is done. The plug wire can be tested with an ohm meter (Google the ohms per foot for spark plug wires, I forget the number) or try a know good spare. Look inside the boot for damage and inside the plug ceramic insulator for cracked ceramic, crud on the ground tip...

Just for grins at some point, might check to verify that the right wires are on the right injectors and spark plugs.

I hear most 4.0s are picky about spark plug choice, entire massive threads have been devoted to that subject here. Post up the plug #s the PO used.

4.0s are notorious for a slight miss at idle. How slight? good question. But the right spark plug helped many solve their slight miss at idle, not all but many.

 

[old_man]

Start it at night where there are no lights. Look under the hood and see if you have any arcing you can see.

 

[Ecomike]

Start it at night where there are no lights. Look under the hood and see if you have any arcing you can see.

Great idea!!!! Amazing what you can see at night under the hood, in the dark, LOL, like glowing red exhaust manifolds and arcing HV SP wires....

 

[Petemech]

So i start up this morning, not only did it take a few extra turns to start but bow it feels more like a dead mis. I'll go through and verify the plug, wire, cap and rotor are ok and check to see if the cap has contact marks. Thing is making me crazy.

 

[old_man]

Start it and when you have a miss, pull one plug wire at a time and then reconnect it. Watch the rpm drop. I you have a cylinder where the rpms don't drop as much, that is your funky cylinder. Pull the plugs and do a visual reading on them. If you aren't familiar with this, take a pix of each plug and post it up. While you are at it, do a compression check across all the cylinders.

This will give you a good idea of what is going on with the engine.

 

[cruiser54]

 

[Petemech]

Plugs i took out looked good. Id say they looked like second row down second colum from the right. The ones i put in were champion copers gapped to .035 i believe.

I'm almost positive this isnt a base engine issue. It has to be a manegment issue.