sudden RPM increase rough iddle

[6.0 Tech]

Yeah, it fits fine. I’ve done it on a number of 03 early 04’s.

Figured you had, if you were recommending it. Looks good, id never tried it.

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[Zeb]

Figured you had, if you were recommending it. Looks good, id never tried it.

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They seem to hold up better. Don’t know if I’ve ever seen one leak like the early version does.

 

[6.0 Tech]

They seem to hold up better. Don’t know if I’ve ever seen one leak like the early version does.

Ive never seen one leak, but ive also never put one in the early spot. I always thought they leaked due to the heat/lack of a pressure drop at the rear of the motor, instead of where the late ones are mounted on the valve cover. Maybe it is just the early sensors are junk. Great tip though bud, never thought of doing that.

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[Long Gone]

Thanks Zeb and 6.0 Tech I will look for that MAT on the driver side, as much as I have been over it I don't know how I missed it.

 

[Zeb]

Ive never seen one leak, but ive also never put one in the early spot. I always thought they leaked due to the heat/lack of a pressure drop at the rear of the motor, instead of where the late ones are mounted on the valve cover. Maybe it is just the early sensors are junk. Great tip though bud, never thought of doing that.

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I’m sure the heat factors in. A lot of the early ones leak around the sealant. The late ones don’t have that sealant but rather more of a crimped together assembly. I think the crimped instead of sealant handles the heat better.

 

[6.0 Tech]

Thanks Zeb and 6.0 Tech I will look for that MAT on the driver side, as much as I have been over it I don't know how I missed it.

That sensor is on the drivers side of the intake, right behind the fuel bowl. Gray connector, looks the same as the eot sensor and the ect sensor plugs.

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[Long Gone]

Oh , but if it were only that easy for me...(nothing is ever easy that is worth doing..) I've worked a bit with thermocouples in industry as an industrial electrician most of it type J some K and others, who knows what type the MAT is really. In the IH literature I've found what they are calling the IA2 (Intake Air Temp2). It says that "when the temperature decreases the resistance of the thermister increases. This causes the signal voltage to increase" It doesn't say if inverse or proportional to temp though. Type J and K go high in all the applications I've ever seen. My sensor was plugged in and still reading -40 on the MAT scangauge2. I unplugged it and it goes to 419. plugged and unplugged several times and it was consistent. Starting the truck with it unplugged and reading 419 led to the same problem as at the -40 reading. Ran ok initially for about 10 seconds and then high RPMs (1100). Not sure what is going on here but since the reading is so off I have to think the sensor is not good, possibly shorting to ground. Not sure this is the root of the problem though. I am really wondering why the check engine light hasn't illuminated through all of this. Especially since the IH literature says "if the PCM recognizes that the IA2 signal is higher or lower than the expected value it will set a Diagnostic Trouble Code (DTC) and illuminate the amber malfunction indicator lamp on the dash" No codes no check engine light.

 

[bismic]

Thank you for the input Zeb and gohouston. I have got those numbers backaswards there for sure, sorry about that. I have suspected that it might have something to do with the ICP, but I was not getting my head around it as the lower value at around 27ish would be running the IPR pretty near closed,(as I was thinking that would still be open a bit) and I could see that would lead to the higher pressure but now as you point out and I am finally remember it if you unplug the ICP it defaults to closing alright, and 27 is closed not just kind of close. Thank you I will get right at looking at that connection etc. I am not getting any codes. I wouldn't think it is anything in the injectors as when it first starts up it will run fine for almost 10 seconds. When I changed the HPOP I pulled the HP oil rails and flushed and blew them out real well. Also blew out the HP oil tube supply lines from the pump through the braided hoses into containers so nothing would get back into the head/block. I tried to suck out the injectors with a turkey baster also but don't think it did much. Did find some things that looked like bunkey balls (repolymerized HPOP screen) in the initial draining of the driver side HP oil rail (the first I pulled), but didn't find any thing more in the drain, cleaning and rinse cycles of the other, nor in the lines. My gut feeling has always been that it was something electrical and I think you have confirmed that, and I know where to go now. I would be surprised if there isn't any oil on that plug. Thanks again.

The IPR duty cycle is ONLY a command from the PCM. It does not reflect a specific valve position. In fact, the IPR is ONLY an open/close valve. The duty cycle dictates the frequency of it closing (it is very fast acting). There is no way to know what the IPR valve is actually doing ..... there is NO position feedback on the actuator or pintle.

With no power to the valve, it defaults to an open position on the actuator, but an internal spring will keep the pintle closed, but the spring isn't a tremendously strong spring.

As far as the IAT2 reading, I would bet on a wiring issue there. You might want to check the resistance of the sensor wiring. I don't have an early 04 manual in front of me, so I can't help on PCM pin locations - maybe others can.

Regarding ICP sensors, I have put an early one on my 06 just to see how it performed. It held up well. Some of the late ICP sensor success is due to the location change, but no doubt it is a better built sensor and will hold up better in the HPOP cover location on the 03 and early 04 MY's.

 

[Long Gone]

Thank you bismic. I didn't realize that the IPR is a bang bang valve, from what I had read I was thinking it was implied anyhow that it was a proportional valve. I saw a video with deiseltechRon talking about the ICP and saying that the % reading was a calculation from other sensor extrapolated from the fact that the motor is running so it is inferred that it is about some (%) value. WOW this seems more like an art than science. I am leaning toward thinking that the MAT sensor is grounding internally as the readings aren't flaky and are constant as I move around the harness with my Scangage2 right in front of me and the key in the on position (gauges active) motor off. They are so repeatable no matter how I move the harness. Since IH says that the MAT is a "thermistor" I'm thinking of wiring a pot through the connector to see if I can dial in a value that would be more in the range that the PCM is looking for. I'm not thinking that this is causing the problem though as I remember seeing the -40 value when I first got my scan gauge and everything fired up nicely and was running just fine.

 

[Long Gone]

Got new MAT sensor and get the same results (-40 when plugged in and 419 unplugged) as with the original. Very consistent from one sensor to the other. No change in temp reading with movement of the wiring harness, and am not finding any loose/corroded grounds. Since the MAT (IAT#2) is an input to the PCM I am thinking the PCM is having a problem. The temp read out in the cab seems to read correctly so it must be getting it from somewhere else (IAT#! or ?). Does anybody know if there are any upgrades or any changes made through the years, are the different years interchangeable or anything else I need to know.

 

[Long Gone]

I replaced the FICM once on this truck about 4 years ago after the truck started behaving inconsistently in that it would run as if some injectors were missing and sometimes hard start. I was trouble shooting bad injectors by using my non-contact thermal gun and had good luck using that method up until that point. Had a shop with a good scanner look at it and they initially said they thought it was a wiring issue and then did a quick FICM swap that did fix the problem. It was one of the few times in the last 20+ years that have had a shop work on one of our vehicles and I felt like I really should have known better and swore not to fall for that again. I could have bought a scanner for myself for the charge and I had to go back and have them put bolts in the degass bottle as it was just floating on top of the motor with no bolts holding it.
The way this starts up cold and runs fine for a short while and then starts romping at a high idle sometimes falling back to 900 then back to 1100 or so just reminds me of how flaky the FICM effected the injectors and the engine performance. Just wondering if anyone has had similar experiences with a PCM and if there are any fixes. I have heard that FICMs can be repaired by re-soldering the components and I am wondering if anyone has experience with the PCMs. I am seriously thinking I need to tear into mine and see what I find. I got a new ICP Original 03-04 style but haven't replaced it yet as I have a 05 style coming and since it is not the easiest to get to I thought I would just do the new style. I really don't have a lot faith that the ICP is going to do much more than the IAT#2 (MAT) sensor. The common denominator looks to me to be the PCM as they (IPR, MAT and ICP) all report to the PCM. I see a used 06 PCM for a reasonable price and am wondering if that would even work or have there been some change like the pin out or configuration, operational voltage, communication protocol to the FICM or something else I am not thinking about.

 

[Zeb]

I replaced the FICM once on this truck about 4 years ago after the truck started behaving inconsistently in that it would run as if some injectors were missing and sometimes hard start. I was trouble shooting bad injectors by using my non-contact thermal gun and had good luck using that method up until that point. Had a shop with a good scanner look at it and they initially said they thought it was a wiring issue and then did a quick FICM swap that did fix the problem. It was one of the few times in the last 20+ years that have had a shop work on one of our vehicles and I felt like I really should have known better and swore not to fall for that again. I could have bought a scanner for myself for the charge and I had to go back and have them put bolts in the degass bottle as it was just floating on top of the motor with no bolts holding it.
The way this starts up cold and runs fine for a short while and then starts romping at a high idle sometimes falling back to 900 then back to 1100 or so just reminds me of how flaky the FICM effected the injectors and the engine performance. Just wondering if anyone has had similar experiences with a PCM and if there are any fixes. I have heard that FICMs can be repaired by re-soldering the components and I am wondering if anyone has experience with the PCMs. I am seriously thinking I need to tear into mine and see what I find. I got a new ICP Original 03-04 style but haven't replaced it yet as I have a 05 style coming and since it is not the easiest to get to I thought I would just do the new style. I really don't have a lot faith that the ICP is going to do much more than the IAT#2 (MAT) sensor. The common denominator looks to me to be the PCM as they (IPR, MAT and ICP) all report to the PCM. I see a used 06 PCM for a reasonable price and am wondering if that would even work or have there been some change like the pin out or configuration, operational voltage, communication protocol to the FICM or something else I am not thinking about.

I seriously doubt it is the PCM. It most likely is the wiring harness, or sensor(s).

 

[Long Gone]

Thanks Zeb. That is encouraging. It may be a while until I can get to it as we just got news that the expected granddaughter is arriving and we are going to have to head there to meet her. It's only 700 or so miles so everything should be here when we get back. Thanks again.

 

[Zeb]

Thanks Zeb. That is encouraging. It may be a while until I can get to it as we just got news that the expected granddaughter is arriving and we are going to have to head there to meet her. It's only 700 or so miles so everything should be here when we get back. Thanks again.

Best wishes on the grand daughter!!!