Unexpained MPG drop

[TSimonson]

Unexplained MPG drop

Please, someone, tell me I'm crazy...
As a long time member, posting a lot of responses to things I've seen before, this is my first "I can't figure this deal out" problem. With my 04.5 baby, I averaged 16.0 MPG (hand calculated) for the first 113,178 miles on the truck. On the last day of my move from Nevada back to Nebraska on 10/2/13 I got 14.72 MPG (after averaging 17.8 MPG on the trip). At the time I chalked it up to maybe a tank of bad diesel. Since then, I've averaged 13.7 MPG over the last 12,318 miles. I thought it might be a change in driving habits or a new area, but when I lived here before, from 2008 to 2011, the same truck averaged 16.10 MPG driving the same roads from home to work and the same hunting trips. I've changed tires, brakes, ball joints, driveline u-joints, replaced the original (48RE) transmission including the torque converter (didn't replace the xmsn to fix MPG, it crapped out on its own) and nothing changed the crappy mileage. I've also noticed that engine response seems pretty sluggish along with EGTs higher than I would expect (850 - 950 just going up an onramp with no load).
I actually brought it to a diesel shop highly recommended by other TDR members in the local area and the shop's recommendation was to get a tuner. Really? I'm not adverse to that recommendation, but I'd like to know what happened to drop the mileage so significantly before I change other variables.
There are no codes thrown from the ECM or PCM. The 5.9L CR is stock, with the after-market adjustable cam angle sensor (checked already, it hasn't moved); the cat is cut out with 4" turbo-back exhaust; Edge Insight CS monitor with turbo timer accessory. Is it possible the cat sensor is bad without throwing a code?
Any help or suggestions are much appreciated.

 

[lpennock]

check for a dragging brake calliper.

Any white smoke on startup or more black smoke when running than you use to have. Could be a leaking injector.

 

[promisedland]

Would a dragging brake be easy to feel in N? Sitting in Ram...
Or blocking up each/checking each wheel?

 

[lpennock]

Easiest way to check would be take it for a drive and coast to a stop then check each rotor with a IR heat gun (or even your hand). If one rotor is hotter than the rest you have found the dragging calliper. Could also be the emergency brakes so check the two rear rotors close to where the emergency brake drum is.

 

[p-Bar]

That shop didn't want to troubleshoot the problem ? Sounds like doctors today just throw prescription drugs at it . What is the XMSN you speak of? You have low miles on it so you may have a dribbling injector . Ask the shop to test the HPCR system each injector can be checked in place. Does the insight monitor rail pressure?

 

[Bob4x4]

Higher egt's? The easiest check is to look for a boost leak.To this day I have found some degree of leak on every truck i have put my pressure tester on.

 

[wcjp]

Flir adapter or IR heat gun for all brake components. Is it 4wd? Temporarily remove the front driveline to be sure no extra drag from the transfer case.

 

[K5IP]

Listen to Bob on the boost leak proposal. The higher EGT temps are a direct clue, especially if you notice a loss of power.
Been there, done that. For me it was a leak in one of the boots.
K5IP

 

[TSimonson]

Thanks for all the feedback. My first thought was a dragging caliper - needed to replace the rear rotors anyway last year. Busted one caliper pulling them off, so replaced both. Checked again today, both the front and rear were within a couple degrees with the IR gun. I'll pull the front driveshaft again to check that - I'm more concerned about a frozen U-joint than the transfer case (didn't replace the fronts when I redid the transmission). But I've been remiss in not looking for a boost leak. DUH! With any luck I'll get to it today and reply to the group. Thanks again!

 

[TSimonson]

Thanks again for all the replies. Here's an update of where I'm at...

- No caliper or brake issues, all four wheels spin nice and easy, and zero delta in temps on the IR gun side to side after coasting to a stop (uphill).
- Ran a tank of injector cleaner, no luck (shocker).
- Pulled the front driveshaft, turns with two fingers, no resistance from front diff or xfer case. No U-joint binding.
- Found a "miniscule" boost leak without putting the pressure tester on. Fixed that, then pressure tested and no other boost leaks. Blew the test cap off @ 15 psi (AIRaid boot is a little bigger than 4" ID). No leaks at the intercooler either. Just fixing that small boost leak got me back to 14.5 MPG from 13.6. Still below 10% the 16.0 average on the first 115k on the truck and I'm doing NO towing now. Input side of the turbo housing was spotless.
- For what it's worth, the "filter minder" position on the K&N cold air box never moves.
- To check for all the fuel possibilities (leak / clogged tank intake / lift pump / HP pump) on my last roadie from Omaha-to-Fargo-Omaha I monitored rail pressure: 20-21 KPSI from 1,900-2,200 RPM. I think that's about right.
- 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). At normal ECT, IAT was about 69-72 with 59 outside air temperature. Not sure if that's normal and I haven't found specs for checking resistance like you could on the pre-2002 independent IAT sensors. Book says you need the DRBIII to check for sensor anomalies.

So unless someone has something I'm completely missing, I'll wait a week and see if the IAT piece helps (not holding my breath) and then I'll get the injectors checked. Thanks again to everyone for the great advice. That's why TDR is the best.

 

[TSimonson]

OK Sports Fans,

IAT cleaning had no impact.

So 5 months in to "seriously" looking at this issue, i finally broke down and brought it to the dealer (no one else would look at it since their "computer doesn't talk to anything newer than 2003"). After a lot of "discussing" back and forth with the mechanics and asking for some additional checks on injectors they don't normally perform, they literally stumbled on to what I'm pretty certain is the cause for the drop in fuel economy and higher EGTs - One of the guys at the dealer accidentally kicked the drain pan with the fuel from the fuel return line to the tank and noticed it was full of metal shavings. I mean full. When they brought me back, it looked a lot like copper and there was also more metal in the fuel return line connection off the rail. I'd dismissed the injection pump early on since I was getting plenty of pressure at the rail at idle and under load. But if I remember right, the bushings in the injection pump are copper, and I'm pretty sure that's the culprit - eating itself slowly.

So based on the metal shavings, my theory is this:
- Pump is still pumping adequate pressure (fact), but has clogged the injectors with metal shavings. This has created a rare situation resulting in adequate fuel pressure with sub-optimal atomization (fuel gets pushed into the cylinder, just doesn't detonate with the efficiency it's supposed to) resulting in lower fuel economy and higher EGTs (fuel energy exits the exhaust valves and is converted to heat / pressure outside of the cylinder).
- I've been living on borrowed time with this injection pump, and pretty soon I'll start getting the classic symptoms for clogged injectors, then the pump will die and the truck won't move.

So my plan is to replace the injection pump and the injectors - soon, like this weekend. If anyone has a better explanation or can shoot holes in my theory, I'm all ears. Just need to know before I take out a 2nd mortgage for repairs

Thanks again.

 

[p-Bar]

this is wild. Usually the grindings are caused from CP3 cavitation increased HP and no aftermarket pump to keep up with the demand . Guess sooner or later they fail.

 

[GrantP]

Hmmm, how much past experience have you had with this dealer? I'm not dealer bashing but I've ran across a couple really bad ones that have provided some seriously wrong (and insanely expensive) conclusions...buyer beware as always. (Again, not dealer bashing...there just aren't any good ones in north Phoenix!) Can you have them do the same test of dumping return fuel into a clean container and verify it yourself? Not saying either you or the dealer are wrong but I'd want the personal verification before I dumped that kind of money.

 

[p-Bar]

Hmmm, how much past experience have you had with this dealer? I'm not dealer bashing but I've ran across a couple really bad ones that have provided some seriously wrong (and insanely expensive) conclusions...buyer beware as always. (Again, not dealer bashing...there just aren't any good ones in north Phoenix!) Can you have them do the same test of dumping return fuel into a clean container and verify it yourself? Not saying either you or the dealer are wrong but I'd want the personal verification before I dumped that kind of money.

Grant as I was reading your post I thought the same thing . A drain pan on the ground Oh that is scientific .

 

[MLee]

Some get a little underhanded to gain extra business. you need to witness this and check it out.

 

[cerberusiam]

The 20-21k psi at those rpms is high for a stock truck just cruising with low load, 17.5-19k at cruise is a lot more reasonable. That in itself would explain loss of economy on a stock tune. The question would be why is that high?

Anything is possible and these will return totally screwed up, but, with that much metal I would expect other symptoms. Hard starting, white smoke, loss of power, etc. Where the CP-3's usually fail puts all that metal directly into the injectors and they simply do not like that much trash run thru them. That does sound a little suspicious if there was a large amount in a drain pan. I would also expect more steel than copper in the filings which further makes one wonder. You could send it in to have it checked if there is any question, but, that is down time and may not be feasible.

 

[Motorhead]

Have you checked to see if you have an exhaust leak at the exhaust manifold, cracked manifold, or an exhaust leak where the turbo meets the exhaust manifold? I had a turbo drive pressure leak at the flanges and I was down on power, low boost, higher EGT's and lower fuel mileage.
Bob 4x4 has a good lead to check too. I made up an adapter with a large white plastic pipe cap wrapped with a little duct tape to bring it up to the right size. I drilled and tapped it to fit a 0-100 psi gauge and also with a male quick disconnect air fitting. I removed the turbo compressor outlet from the rubber boot and installed the pipe cap adapter into the rubber boot and clamped it. I CAREFULLY charged the whole intake, inter cooler with compressed air to about 35-40 psi MAX and watched the gauge. I sprayed soap water around all fittings and joints. I found my boost gauge fitting leaking.

 

[Prairie Dog]

Higher egt's? The easiest check is to look for a boost leak.To this day I have found some degree of leak on every truck i have put my pressure tester on.

Is there a common location you usually find these leaks? Failed hose, loose clamp, etc?

 

[lpennock]

Is there a common location you usually find these leaks? Failed hose, loose clamp, etc?

Boost gauge connection.

 

[TSimonson]

OK,
So it's been a while and I figured I owed the group an update. True, I was a little concerned about the scientific drain pan method at the dealer, but after pulling the CP3, it was shot. I'm amazed it ran at all. Replaced the pump and all the injectors. No significant change in power or MPG. I finally broke down and started logging ECM data for every trip. I noticed that typically IAT was only about 17*F above ambient and varied only a little bit between 0 and 23 PSI boost (IAT 77*F at 0 PSI boost, IAT 71.6*F @ 19 PSI boost). I thought that was low (ambient 55*F), but I assumed the logger was measuring the wrong PID - I thought it was logging inlet temp (between the airbox & the turbo) not intake temp (at the manifold). After running it by a buddy of mine, he was pretty sure the IAT was being accurately reported and a problem - keeping the ECM in "winter emissions mode". So a week ago I tested my "wrong PID" theory and took the heat gun to the inlet temp sensor and it didn't change the logged (intake) temp at all. So I replaced the IAT/MAP sensor last week (3/29). With limited testing, IATs are about 25*F above ambient, but not enough data yet. Still seems low to me. With cruising EGTs in the 500-600*F range, I would guess IAT would be around 75-100*F (assuming ambient of 50*F). More to follow...