Miss At Idle

[dorkweed]

This is for the old '99 that the parents have now. It's got a "miss" at idle............but only after the engine has gotten up to operating temp. Cold idle is normal with no miss. It's a miss, but the computer adjusts by increasing the idle speed slightly after warm up.. Running up and down the road, she runs as good as ever. Dad says she's been averaging 19mpg most every fill up. What should I look for and check to diagnose this??? Thanks guys!!

[CSM]

I would loosen injector lines to see if I could isolate the "miss." If its a particular cylinder missing, it could be several things causing inconsistent power from that cyl. My old 2000 had a similar issue once in a blue moon, even with new bosch injectors and it ran and drove fine for years. I think that it went away once I put a new VP in it though.

[Mopar1973Man]

Got the same problem. Dirty injectors. I can pull them out clean them and then the problem is gone. Just dragging tail about doing it again. Actually this time I'm going to have them pop tested and calibrated if I pull them out. Now seeing ISX new method of cleaning injectors I'm going to grab a can of carb dip and clean mine with that...

[rickf]

Got the same problem. Dirty injectors. I can pull them out clean them and then the problem is gone. Just dragging tail about doing it again. Actually this time I'm going to have them pop tested and calibrated if I pull them out. Now seeing ISX new method of cleaning injectors I'm going to grab a can of carb dip and clean mine with that...

Link to new cleaning method?

[CSM]

Berrymans B-12 ChemTool

[Mopar1973Man]

Link to new cleaning method?

Here you go... ISX is improving the method...

http://forum.mopar1973man.com/threads/7555-Injector-Cleaner-that-works

[dorkweed]

Got the same problem. Dirty injectors. I can pull them out clean them and then the problem is gone. Just dragging tail about doing it again. Actually this time I'm going to have them pop tested and calibrated if I pull them out. Now seeing ISX new method of cleaning injectors I'm going to grab a can of carb dip and clean mine with that...

But why only after the engine reaches operating temperature????

[Mopar1973Man]

But why only after the engine reaches operating temperature????

Because as the injector is cool there is ample room for the pintle needle to move but as the nozzle heats up the coked fuel on the needle and nozzle body take up the last bit of space and then at idle you get a stuttering injector because the pop pressure isn't high enough to fire the injector because its jammed up. But you'll notice if you leave the engine idle long enough to cool the injectors again the problem will disappear again. Also just turning on the A/C or hard brake pedal push the problem goes away (increased load on the engine also a increase in pop pressure). I've got a pop a while back where I measured everything during a injector cleaning and was seeing a slight change in measure before and after. Mine are short lived because there already high mileage injectors from CajFlynn. (+400k miles).