Marty
New member
Well I have a truck here in the shop and I have not experienced this issue before and I can not for the life of me figure it out. I am hoping someone on here can give me some place to turn.
Here is the story:
Truck went to another shop before coming here for the same problem.
ISSUE: Truck rpm oscillates @ idle. Almost sounds like it is going to die at times. Unplug the ICP sensor and it idles perfect, but with 1280 code obviously.
The oscillation started while the customer owned the vehicle. It was not there prior to purchase. It has over 211k miles. Oil level is perfect.
Previous mechanic, replaced trans selector switch, did ICP sensor and pigtail and then also did TPS sensor.
Issue still there, so mechanic unplugged ICP sensor and told the customer his diablo sport programmer wouldn't clear off his PCM. Then he told him his PCM was bad and sent him on his way.
Wellllll... despite the fact I didn't think the PCM was the problem, I swapped it with another PMT1 DPC 422 out of an identical truck. No change. I also swapped IDM’s. No Change.
I checked the resistance at the ICP sensor plug. All were in spec according to fordinstallersupport.com. I also put another ICP sensor in from FORD just to be sure. Swapped in a brand new test IPR. No change, I replaced the pigtail on the IPR because it had dirt caked inside of it. No change. I checked continuity from PCM to the 42 pin and the ICP/IPR. They were all <1. I have not tried a whole new harness but I have tested continuity from one end to the other, there is NO interruption. Wiring looks fine, and unplugging injectors individually make the truck run with a miss, but the oscillation is still there regardless. Injectors have been removed from the circuit individually. There is no change in oscillation, only a miss until that injector is plugged back in. When doing a contribution test, it gives me cyl #8 as failing the contribution. However, I understand how a contribution test works and I do not think that has anything to do with my problem. Unplugging the icp sets it to a default reading(725 psi). It bumps up the ipr(15-16%) since it doesn't know an actual icp value. This will raise your icp enough for it to idle smooth. This however is just from the seat of the pants “feeling”. In reality using the SCOPE, I have found that it is still doing it, but just isn’t noticeable to the person.
I swapped HPOP's, still does it. I pressurized each head individually. Both held pressure.
Oil looks fine running. Did an oil change regardless with new 15w40. Oil Level Perfect.
I de-pinned the alternator plug and one of the alternator wires at one point seemed to eliminate the idle issue. However hindsight was just that it was taking the load off the engine and reducing the oscillation feeling. The alternator was replaced regardless.
Fuel pressure idle 60. Checked fuel @ rear of driver head and front of passenger head (end of the rail) and it stayed 60.Fuel quality good, fresh and I have gone over a full tank of fuel testing this truck out.
F250 so no delaminated tanks like in 450/550 trucks.
Icp v is going from 0.66-1.30 @ idle. Psi readings are 453-637.
Ipr says 12-13%
Rpm 630-713
Very noticeable at idle.
Accelerator pedal pos voltage idle .61v wot 3.93
It does it in ANY gear selection. Park, Reverse, Drive, 2nd, 1st as long as it's idling.
The customer has also stated that the truck has been shutting off recently now. Never did before.
I ended up swapping out the injectors, no change. I removed the transmission and all of the plugs on the transmission and got the truck up to operating temperature and no change. I had the drive belt off the truck as well, no change.
So this problem can’t be anything in the HPOIL system itself, the trans or the accessories.
I have narrowed down the problem (but still haven’t solved it) using the help of a friend with a SCOPE.
The 5v signal wire coming from the ICP sensor is sporadically going haywire. When unplugging the sensor to check resistance the truck was not interpreting a reading. Therefore the wire’s resistance was within spec. I tapped into the wire WHILE running using a scope. The signal gets wacky randomly and I have captured this on screen. I also used the scope to monitor actual ICP pressure. While the pressure of the oil stayed relatively consistent…. The 5v reference from the sensor goes haywire. Wiggling wires around while the truck is acting up does not change anything. Currently we are trying to verify all grounds are good and maybe we will add a ground from the alternator to the battery to help eliminate any electrical noise that may be entering this trucks' system. I will post the pictures that show this.
Here are the IDS readings that originally made me think something was up with the ICP.
The BLUE is erratic ICP 5v reference. The Red is the actual ICP reading from the head. When the truck is not acting up, the blue and the red lines mirror one another. The SCOPE is powered via its own battery so no electrical interaction is occurring. The blue line on the SCOPE is tied into the 5v wire coming from the ICP sensor. The Red is coming from the SCOPE's own pressure transducer that is fitting into the driver side head on the 3rd plug back.
This problem is not the sensor because when I added a resistor to the sensor wiring harness to keep the pressure from bottoming out to less then 500 psi... it still oscillates. I also swapped at least 3 ICP sensors into this truck now including a known working good one. Also when the ICP sensor is unplugged, it still does this, just it is not noticeable by seat of the pants as mentioned earlier. You can still see it on the SCOPE.
Then we took a potentiometer and we have it set at a steady .8v so the truck reads a steady 540 psi. It idles perfect. We reconnect the ICP sensor and it will eventually oscillate again.
At this point today even though I have already cleaned grounds, installed new batteries... we are checking to see if any grounds are making "electrical noise" in the system anywhere somehow.
Here is the story:
Truck went to another shop before coming here for the same problem.
ISSUE: Truck rpm oscillates @ idle. Almost sounds like it is going to die at times. Unplug the ICP sensor and it idles perfect, but with 1280 code obviously.
The oscillation started while the customer owned the vehicle. It was not there prior to purchase. It has over 211k miles. Oil level is perfect.
Previous mechanic, replaced trans selector switch, did ICP sensor and pigtail and then also did TPS sensor.
Issue still there, so mechanic unplugged ICP sensor and told the customer his diablo sport programmer wouldn't clear off his PCM. Then he told him his PCM was bad and sent him on his way.
Wellllll... despite the fact I didn't think the PCM was the problem, I swapped it with another PMT1 DPC 422 out of an identical truck. No change. I also swapped IDM’s. No Change.
I checked the resistance at the ICP sensor plug. All were in spec according to fordinstallersupport.com. I also put another ICP sensor in from FORD just to be sure. Swapped in a brand new test IPR. No change, I replaced the pigtail on the IPR because it had dirt caked inside of it. No change. I checked continuity from PCM to the 42 pin and the ICP/IPR. They were all <1. I have not tried a whole new harness but I have tested continuity from one end to the other, there is NO interruption. Wiring looks fine, and unplugging injectors individually make the truck run with a miss, but the oscillation is still there regardless. Injectors have been removed from the circuit individually. There is no change in oscillation, only a miss until that injector is plugged back in. When doing a contribution test, it gives me cyl #8 as failing the contribution. However, I understand how a contribution test works and I do not think that has anything to do with my problem. Unplugging the icp sets it to a default reading(725 psi). It bumps up the ipr(15-16%) since it doesn't know an actual icp value. This will raise your icp enough for it to idle smooth. This however is just from the seat of the pants “feeling”. In reality using the SCOPE, I have found that it is still doing it, but just isn’t noticeable to the person.
I swapped HPOP's, still does it. I pressurized each head individually. Both held pressure.
Oil looks fine running. Did an oil change regardless with new 15w40. Oil Level Perfect.
I de-pinned the alternator plug and one of the alternator wires at one point seemed to eliminate the idle issue. However hindsight was just that it was taking the load off the engine and reducing the oscillation feeling. The alternator was replaced regardless.
Fuel pressure idle 60. Checked fuel @ rear of driver head and front of passenger head (end of the rail) and it stayed 60.Fuel quality good, fresh and I have gone over a full tank of fuel testing this truck out.
F250 so no delaminated tanks like in 450/550 trucks.
Icp v is going from 0.66-1.30 @ idle. Psi readings are 453-637.
Ipr says 12-13%
Rpm 630-713
Very noticeable at idle.
Accelerator pedal pos voltage idle .61v wot 3.93
It does it in ANY gear selection. Park, Reverse, Drive, 2nd, 1st as long as it's idling.
The customer has also stated that the truck has been shutting off recently now. Never did before.
I ended up swapping out the injectors, no change. I removed the transmission and all of the plugs on the transmission and got the truck up to operating temperature and no change. I had the drive belt off the truck as well, no change.
So this problem can’t be anything in the HPOIL system itself, the trans or the accessories.
I have narrowed down the problem (but still haven’t solved it) using the help of a friend with a SCOPE.
The 5v signal wire coming from the ICP sensor is sporadically going haywire. When unplugging the sensor to check resistance the truck was not interpreting a reading. Therefore the wire’s resistance was within spec. I tapped into the wire WHILE running using a scope. The signal gets wacky randomly and I have captured this on screen. I also used the scope to monitor actual ICP pressure. While the pressure of the oil stayed relatively consistent…. The 5v reference from the sensor goes haywire. Wiggling wires around while the truck is acting up does not change anything. Currently we are trying to verify all grounds are good and maybe we will add a ground from the alternator to the battery to help eliminate any electrical noise that may be entering this trucks' system. I will post the pictures that show this.
Here are the IDS readings that originally made me think something was up with the ICP.
The BLUE is erratic ICP 5v reference. The Red is the actual ICP reading from the head. When the truck is not acting up, the blue and the red lines mirror one another. The SCOPE is powered via its own battery so no electrical interaction is occurring. The blue line on the SCOPE is tied into the 5v wire coming from the ICP sensor. The Red is coming from the SCOPE's own pressure transducer that is fitting into the driver side head on the 3rd plug back.
This problem is not the sensor because when I added a resistor to the sensor wiring harness to keep the pressure from bottoming out to less then 500 psi... it still oscillates. I also swapped at least 3 ICP sensors into this truck now including a known working good one. Also when the ICP sensor is unplugged, it still does this, just it is not noticeable by seat of the pants as mentioned earlier. You can still see it on the SCOPE.
Then we took a potentiometer and we have it set at a steady .8v so the truck reads a steady 540 psi. It idles perfect. We reconnect the ICP sensor and it will eventually oscillate again.
At this point today even though I have already cleaned grounds, installed new batteries... we are checking to see if any grounds are making "electrical noise" in the system anywhere somehow.
