Unexpained MPG drop

[AH64ID]

On my truck the IAT, in the intake manifold, runs about 12-18° above ambient under normal circumstances and will only get to 35-40° above ambient on HOT days while towing hard up a hill at high boost.

Do you have an adjustable cam or crank angle sensor? You said it was good, but I would check it again.

 

[sojoe]

Winter blend diesel???

 

[TSimonson]

First, thanks for all the replies. I'm still working this.
AH64ID - I do have an adjustable cam sensor. Crank is stock, but I will check both again. It'd be "funny" if that was it since it was the first thing I checked.
sojoe - I initially assumed winter blend, too. But it's been persistent for 3.5 years across different fueling places from MO to ND, so I think winter blend and fuel quality is out.
As a quick recap...
Oct 2014 - MPG drop (~15%)
Nov 2014 - New tires and alignment
Feb 2015 - New transmission (it ate itself)
Mar 2015 - IR gun the rotors to check for dragging
Aug 2016 - New CP-3 and injectors (pump was shot)

And the irony is that I moved from NV to NE in Jul 2014, 20k GVW towing a car over the Rockies and averaged 15.9. I haven't towed a thing since then and I'm averaging 13.7 for the last 40k miles.
Again, I'm still working this. Not enough data from the IAT swap, but I'll definitely let the group know. Thanks again!

 

[TSimonson]

New IAT sensor didn't make a difference - still trying to figure this out. Swapped cam and crank angle sensors - no change. Finally bought an OBDII data logger and made a bunch of runs but nothing sticks out to me in the data. I'm almost down to a stray electron spontaneously flashed the ECM and I'll just turn my Edge CS into a tuner... Any advice is still appreciated.

 

[Tuesdak]

Check the blowby on the engine. The K&N sticks out as a ring dusting...

 

[Ozymandias]

Check the blowby on the engine. The K&N sticks out as a ring dusting...

Thats what I thought reading through this thread, no one said a word about the K&N.
Lately i had one of this setups in my hand and there the pre-Turbo IAT was just taped to a sheet metal - it was not installed in the airway itself - to me that can not work out properly this way, the temp information that this sensor delivers must be wrong that way.

Especially because the owner of the Truck is also complaining about worse MPG, he bought the truck that way.
I told him to get rid of that crap and install a stock airbox ASAP.

 

[Ozymandias]

Finally, tonight I pulled both the pre-turbo IAT and IAT/MAP sensors and cleaned them up. O-ring on the IAT/MAP on the intake manifold was dusty in one spot that took up about a quarter of the diameter and the seat on the manifold under the sensor was super dirty (dust - used to live in the desert). A

This makes my Alarm sound!

 

[TSimonson]

Almost 4 years into this ordeal, still hating 13.0 MPG hand calculated, low power and high EGTs. For JD & Ozy, thanks for the input, but my airbox is an AIRaid, no K&N involved anywhere. After all the machinations, I think my ECM is bad. After monitoring a lot of ECM outputs on my multi-gauge, and looking at the logging, I just can't figure anything else out. Back in 2007, the old lift pump was spewing fuel everywhere including right over the ECM. I had that LP replaced under a recall warranty. Then had the lift pump moved to the tank under a recall in 2009. Truck starts and runs fine, but feels like an old dog that won't hunt anymore. I'm hesitant to tow anything until I get this fixed. I've uploaded a couple logs from my OBDII. If anyone has any ideas other than ECM, I'm all ears. I can only upload the pdf, if anyone wants the raw data I'm happy to forward to fix this issue, just PM me. Thanks again to the awesome TDR community.

 

[cerberusiam]

You didn't change tires in there anywhere and now the measured miles are off? Have you verified the mileage driven is at least close to actual miles on the Odo?

 

[Tuesdak]

New IAT sensor didn't make a difference - still trying to figure this out. Swapped cam and crank angle sensors - no change. Finally bought an OBDII data logger and made a bunch of runs but nothing sticks out to me in the data. I'm almost down to a stray electron spontaneously flashed the ECM and I'll just turn my Edge CS into a tuner... Any advice is still appreciated.

No difference as in the sensor is still reading wild inaccurate temps? If so it's time to breakout the volt meter and measure the sensor from the ECM plug and compare it to known values that should be in the shop manual. I have seen bad connectors send many sensors and ECM's back for warranty while not fixing the bad connector problem. If the ECM thinks it's cold it may be in a warm-up mode and delay locking the TCC and that eats MPG. Just saying.

Did the dealer address the temp sensor reading concern? Did the dealer test the lift pump pressure after the CP3 repair? New fuel filter would be assumed, but, is it?

Again how is the engine for blowby? Dirty MAF sensor or other dirt in the intake means dirt is getting into the engine somehow.

Have you inspected the turbo for the wheels hitting the housing? I don't know the OEM boost that they should provide, however, a stuck wastegate would answer the high EGT and low power. EGT, is this a before and after high EGT measurement or measuring now and it's over 1350 so it must be high? Some stock tunes are known to run what some would say is high EGT so I am verifying if this is a solid clue.

You checked for boost leaks. Why not check again?

Exhaust leaks? Do you have a cat? Clogged exhaust via melted cat are a possibility. Crushed pipe, collapsed pipe, failed muffler (would be noisy IMO), are possible.

Edit: after looking through the logs with engine power at 90% you got 15 PSI of boost. In the mirror is it smoking black? Best I can tell you should be at 26PSI for stock boost: https://www.turbodieselregister.com/threads/what-is-stock-max-boost-on-the-2004-5.135406/

 

[TSimonson]

Thanks for the replies!
- Yes, I did change tires about 1 month after the issue started, but they're the same size - stock. Miles driven are almost spot on to the odometer - negligible delta.

- "No difference" with new IAT sensor meaning no noticeable change in performance. As you can see in the logs, post intercooler IATs are what I think I would expect based on ambient temps. I can't see anything based on the logs that would lead me to believe ECM is cold and in warm-up mode. That was one of my early theories, but after looking at the logged data, I threw that theory out as ECT, ambient temps and IAT reported by the ECM don't fall in the warm-up mode window.

- I don't know if the dealer tested the LP pressure after replacing the CP3, but the ECM is reporting 20-22.5k psi rail pressure, so I don't think it's the LP or CP3. And yes, new fuel filter. 7 new filters since 2014 when the problem started.

- O-ring on the MAF sensor was pretty dirty, but there was just a little carbon on the MAF sensor itself, about what I'd expect after 145,000 miles.

- Turbo looked great when I checked for leaks. No rubbing against the housing and the vanes were in great shape. I always use the turbo timer.

- I need to look at the wastegate. When checking for turbo leaks, I could only get about 10-12 psi before the test cap would shoot across the garage. I didn't think the wastegate would open until around the 20 psi range, but I'll check that next.

- "High" EGT is anecdotal. I don't have any pre-2014 data, so it's just my gut. I'm basing that on the fact that now I'll routinely see 1100s (pre-turbo) on the local freeway on ramps when I'm empty and I only remember seeing that range when I was hauling cars over the Rockies in July. So that may or may not be a solid clue. It is NOT a before and after EGT comparison.

- Cut the cat out in '09, no exhaust crimps, I guess it could be a failed muffler, but it doesn't sound any different than it used to and I didn't think mufflers failed all at once. I thought that would be a gradual decrease as the muffler "filled up". It's a thru-flow MBRP that I only put on in '09 so I don't think that would be it.

- I don't see any calculated load values over 60% in the logs, granted the ones I posted are almost unusable. I re-posted better logs. But to answer the question, yeah, if I stand on it, I get a good 1-2 seconds of black smoke. But if I'm standing on it, I'm seeing 23-26 psi of boost. Again, I have no pre-2014 data logs, but I "think" my boost is actually a little higher than it used to be. All the more reason to check the wastegate.

Here's another thing I don't understand. The ECM thinks I'm getting about 22-25 MPG if you look at trip fuel vs. trip distance. That also shows up real time on the gauge - 65 MPH on the freeway empty = 25-32 MPG as reported by the ECM. That leads me to think lift pump or ECM (or bad ECM connection).

So at the end of the day, I'm looking for a single cause for loss of power, lower efficiency, and anecdotal high EGTs that are all unchanged after replacing the transmission, CP3 and injectors. In this order I'm looking at 1) Stuck wastegate; 2) Bad lift pump (I need to test isolated from CP3); 3) Bad ECM. Thoughts?

 

[Tuesdak]

Can't read the new logs at the moment - will look at later. Thanks for the clarification.

Don't need high pressure to test leaks. If the wg moves 1/16 1/4" by hand it should be ok. I assume mechanical WG.

I have had trouble with the Dodge brake switches sticking on causing the trailer brakes to make starting off interesting. This stuck switch would keep the TCC from locking up for an automatic.

Fuel leaks including into crankcase? Any oil analysis done?

Black smoke? Just a haze or blocking out the sun? My HO 2003 stock would only haze so this is a good clue. Just has injectors dumping more fuel than they should. Maybe repair didn't get all the derbis and ruined new injectors.

Rats nest in fender - I had one under the air filter. Needless to say it failed emmisions snap test over that.

Pipe delamination and internal collapse on exhaust - common on 6.5TD crossovers. Roll a golf ball through the pipe to test.

Blowby test could say if you broke a ring, but, don't see any MPG complaints with broken rings.

 

[MGreer]

Going off lower power, higher exhaust temps and a boost range of 23-26 psi it sounds like you have a waste gate issue. You should be seeing around 32 psi boost at least briefly on a stock truck .A couple years ago the waste gate solenoid went bad on my truck and it wouldn't build over 23 psi.
You can do a search with " holset he351cw " and a link for the service manual should pop up. It walks you through testing the turbo. If you haven't tried it yet you can crimp off the hose to the actuator and see if your boost goes up. Be careful not to over boost, I believe it will set a code around 34 or 35 psi. Holset calls the solenoid a command valve.

Hope this helps

 

[cerberusiam]

If you are still seeing 19-21k on steady cruising something is causing the ECM to demand that. With a stock tune it really should not exceed 17k at steady low load cruising and really never exceed 19k unless you have a lot of rpms and WOT. The 23-26 psi max boost is likely the WG actuator has failed, you can test that by crimping the boost reference hose on the fornt of the turbo with a small pair of vice grips. That should give you well into the 30's with even stock fueling and high rpms. It should set a DTC and maybe even derate when you do that as that will be over boost condition on a stock tune. The fact you aren't getting a DTC now and the mpg calculation is so far off definitely suggest you have an ECM issue, if you crimp the boost ref hose and you get no DTC's then that scenario is even more likely. This is assuming you do NOT have any programming or add-on box doing something.

 

[TSimonson]

Again, my thanks to JDormire, MGreer and cerberusiam for your suggestions. Finally finished sodding the yard tonight so hopefully I can look more into the WG tomorrow. To answer some of the above questions...
- WG has the solenoid - I downloaded the Holset manual and hopefully I can really check that out tomorrow
- I unhooked the Prodigy brake controller to see if that helps the torque converter
- No oil analysis completed, but oil level is never high and it doesn't smell like diesel, so I haven't checked. I also put some dye in the fuel tank, no leaks, no indication of diesel in the oil at the next oil change, but I don't know if UV dye works in oil...
- Black smoke when I stand on it is just a haze. Same thing I've seen since '04 when it was new.
- No rats, squirrels, mice, cats, etc in the AIRaid box, although I did have that in my old '85 Jeep CJ-7 once. Mice also wreaked havoc with a lot of ground wires
- I'll put pipe delam on the list to check, but the stainless exhaust is not even 10 years old. I'll check, easy enough
- IAT sensor was pretty clean, especially compared to the inlet sensor (easy comparison), so I don't think that's the issue.
- Fuel rail pressure of 20-22.5k psi was just a test to see what I could get standing on it starting at 80 MPH. Cruising it's 14-16k psi
- I can never get more than 23-26 psi boost (empty - haven't towed with this truck in 4 years. Too concerned about power & EGTs). Never in the 30s anymore
- No programmer or add-on box. It's stock except for exhaust and air box

So my plan is to crimp off the hose going to the mechanical side of the WG and see if I get better boost. I'll make a run without and one with the crimp. If the boost is different, is there a way to tell if it's the solenoid or the ECM? Or do I just overboost and see if I get a DTC? If no DTC, then ECM. If there is a DTC, then solenoid. That being said, I'll probably try the solenoid first in any case, then the $1k ECM

Thanks again, you guys have been a huge help!

 

[MGreer]

After dealing with my issue I'll share what I learned and what worked. The first thing is that the wires going into the waste gate solenoid are prone to becoming brittle and breaking. I would visually inspect these wires the best you can.
The next test would be a resistance test on the solenoid itself. I believe the repair manual spec is a minimum of 6 ohms at 20 degrees C.
On my truck the ohms were out of spec and then I crimped the supply hose off. The boost came back and the truck ran great. I took the solenoid off and it appeared to be clean.
I bought a used solenoid off eBay for about 70 bucks, tested the resistance which was in spec, installed solenoid and all has been good ever since.
If you have to remove the solenoid it takes a thin 1 inch wrench. I bought a set of wrenches from hf and ground one down.

 

[MGreer]

In reference to it being an ecm problem or not will be hard to determine, best I can remember is the waste gate solenoid is triggered from the ecm by a signal from the map sensor.
Hopefully someone with more in depth knowledge than me will chime in.

 

[lpennock]

Westgate solenoid is a normally open device that is controlled by a pulse width modulated signal from the ECU. The mechanical wastegate is set about 24psi and the Solenoid allows boost to be controlled by the ECU. Stock programming allows boost to peak at 32psi and then pulls it down to the 28-30 psi range.

When solenoid fails you will max out boost at about 24psi. Since fuel tables try to boost to 32psi you will smoke and get high get.

Not likely a ECU problem as it is only the driver. You can measure the voltage on the Solenoid but it isn't easy as duty cycle at idle is 0%. I can't remember if you needed load to get enough duty cycle to measure voltage so I'm not sure if you can just rev the engine to send to normal 90% duty cycle, about 10v on a voltmeter.

 

[TSimonson]

Thanks again to all for the suggestions. After replacing a caliper on my son's car on FRI after work and re-wiring the spare bedroom on SAT afternoon, I finally got a chance to take a look at this wastegate.
Since I had the time, I decided to forgo the vise grip test and did the high power and resistance tests in the Holset manual. As mentioned by MGreer, the minimum is 6 ohms at 20 C. Last night I got 11.1 ohms at 10 C in the garage, so it meets the minimum, but that seems a little high to me since I figured decreasing temps should reduce resistance. No chafing at the entrance to the solenoid, and wires weren't as "fresh" as you'd expect from the factory, but not too brittle after 14 years.
Previously I tried to move the wastegate lever by hand. It wouldn't budge. Last night I put the recommended 45 psi on the actual wastegate valve. It didn't move at first, but after 15-20 applications, it moved smoothly every time. It did not move below 45 psi.
I also noticed a lot of soot on the firewall around the downpipe. Pic attached. Not good, so I tightened the v-clamp there about 3/16" inch.
Since the resistance test passed and I got the wastegate pressure test to pass, I decided to start the engine without the wastegate solenoid attached to see if the ECM would throw a code. It did - P0243, so I thought that was a good sign the ECM was good at least as far as the wastegate circuit goes. Cleared the code and went to bed thinking the initial sticking manual wastegate problem was fixed.
Now today, got in the truck to run to Lowe's and the P0243 (wastegate circuit) was back. Truck actually ran better on the short trip, but CEL remained on after trying to clear a couple times. Pulled everything apart again. This time solenoid harness read 11.3 ohms at about 11 C. Also checked voltage to the harness from the ECM with the engine off and the key in the ON position and read 12.4V.
Put everything back together, and still can't clear the P0243. The solenoid looks terrible, probably due to some water pump leaks 6-7 years ago (pic attached). So here's my new thinking:
- Exhaust leak off downpipe was a big problem, maybe the source of the whole power/EGT/efficiency problem?
- Wastegate was sticking, but sticking in the closed position. I think that I'd get more boost "without a wastegate" and that shouldn't matter below ~24 psi boost. Is that right?
- Even though the solenoid passes resistance test, I think it's bad based on persistent P0243. While the solenoid might be bad and is probably the cause of the CEL, I don't think this is the power/EGT/efficiency issue. The solenoid (command valve) only keeps the wastegate closed at high demand points (above ~24 psi). From the factory manual, "
Actuating the command valve does not increase boost pressure if the boost pressure is below the wastegate actuator setting."
The above still leaves me with questions...
- Should the solenoid be getting a signal from the ECM with the engine off? Does the "pulse width modulated" signal change voltage that I'm reading? I'm guessing yes.
- If the mechanical wastegate is limited to 24 psi, why wouldn't it move below 45 psi from the external compressor?
- Not mentioned above, but ECM is reporting 1kpsi at the rail when the engine is off while turbo timer is counting down. Is that right, or a signal of a problem with the ECM?

So maybe we're on to something here, or maybe it's another red herring. Thanks again to everyone who's contributed. I hope to add to other TDR members' posts when I finally answer this stumper.

Cheers.

 

[DavidC]

Just a FYI for voltage checking. You can check with a meter but you could be reading electronic saturation which could be a ghost reading. To verify use a 12vdc test lamp and find out if it lights up, that will tell you if voltage is truly there or not as it will put a load on the circuit.

Dave