So I’ve been having this problem with my truck, it randomly started the other day, when the truck warms up at an idle it sounds likes it missing, when I am driving it and hold it at a steady rpm around 1500 it surges and then when you rev it up, or let off the throttle to while it is in gear it takes a while to idle back down. I already tried to clean the injectors and changed the fuel filter and the water separator. Don’t know what else to do. Anybody know what’s going on?

Before tearing out the APPS or even thinking its a APPS issue. Take a live data tool like OBDLink or ScanGauge II and watch the TPS value. Does it float or change when held at a point of throttle? If it wondering or jumping value then I say change the APPS sensor. 

 

As for the warm engine idle miss that could be a injector that is popping low or bad spray pattern. Still possible as part of this issue.

 

As for the hold at 1,500 and surge could be a AC noise issue. Either test the alternator on a bench or you could use a DVM and check the AC voltage from the alternator with everything off and the engine idling it should not be above 50mV AC. This only works if you have a DVM with a 2V AC or less setting. AC noise can produce a surge in the ECM signals.

 

I've gotta ask did you do a W-T ground wire mod? This would resolve the A/C noise problem. 

 

As for testing the noise...

 

6 hours ago, dave110 said:

 

It is if it's leaking. May not be the rough idle problem but should be fixed before it causes another

Very true. 

My vote is also injectors, but... there is always but...

Need to haul something heavy for a while and see if it comes out 

On 9/6/2019 at 10:27 PM, Mopar1973Man said:

Before tearing out the APPS or even thinking its a APPS issue. Take a live data tool like OBDLink or ScanGauge II and watch the TPS value. Does it float or change when held at a point of throttle? If it wondering or jumping value then I say change the APPS sensor.

 

 

When held at about 1300rpm its jumping back and forth from 11-11.4 on the absolute throttle position%

When held steady, should be steady. Get a timbo apps.

As for rough idle when worm, apps has nothing to do with it, ecm is in direct control at idle. 

8 hours ago, Dmann said:

When held at about 1300rpm its jumping back and forth from 11-11.4 on the absolute throttle position%

 

That is steady enough. Not seeing any 0% or 100%  or other wild numbers while held steady right? Then the APPS is good then. 0.4% TPS change is nothing and acceptable.

4 hours ago, Mopar1973Man said:

 

That is steady enough. Not seeing any 0% or 100%  or other wild numbers while held steady right? Then the APPS is good then. 0.4% TPS change is nothing and acceptable.

No nothing wild. I’m starting to lean toward my vp because I noticed last night loud injector clatter coming from the fuel lines from vp to the head. However it’s not throwing any codes still 

5 hours ago, Dmann said:

I noticed last night loud injector clatter coming from the fuel lines from vp to the head.

 

Could be injection pump issue but I'm not going to point that direction yet. 

 

Now using a live data tool like OBDLink LX or ScanGauge II at key on you want to look at both ECT (coolant temp) and IAT (intake temp) should match. If IAT is lower than normal timing is advanced. If the IAT is higher than normal then the timing will be retarded. Typically at key on the two values match (no block heater). Now during driving, fully warmed up the IAT will be about +40*F over outside temperature. This is just a rule of thumb. ECT should be in the 190 to 200*F range normally fully warmed up. These two temperatures can affect timing.

 

Then how many miles on the injectors? If the injectors have over 100k miles then the injectors could be popping too low. 293 bar is the bottom limit for injectors according to the Dodge FSM. Just my factory stock injectors at 150k miles where as low as 260 bar, still ran good, fuel mileage was down but still functional. Just because it runs doesn't mean it spraying fuel with a good pattern and atomization could be poor.