Lost mpg
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Lost mpg
We have a 1999 RV (E450 Super Duty) that we've driven over 80,000 miles in 6 years. At the 113K - 119K miles area, we were getting about 9.5 mpg. At 127K, we got misfires and, after changing coils etc. finally got a rebuilt engine installed. (We full time in the RV). The mpg had dropped at about 124K to 7.6 mpg or so. (I attributed this to the misfires, coil issues etc.)
After the new engine ($9K+) I had hoped to be back at 9.5 mpg or so. No such luck. After driving 3K miles on the new engine, we're still getting 7.6 mpg or so. The new engine got new Motorcraft coils from the old engine, engine came with spark plugs, and the only sign that there's anything wrong is an airbag light on (this was not the case immediately after the new engine got installed). I had purchased a bluetooth OBD interface which shows no errors. I did put on new tires shortly after the engine change, and run the same pressures as before. Same brand of tire.
Anyone have any ideas on how to get our old mpg back?
Thanks in advance!
After the new engine ($9K+) I had hoped to be back at 9.5 mpg or so. No such luck. After driving 3K miles on the new engine, we're still getting 7.6 mpg or so. The new engine got new Motorcraft coils from the old engine, engine came with spark plugs, and the only sign that there's anything wrong is an airbag light on (this was not the case immediately after the new engine got installed). I had purchased a bluetooth OBD interface which shows no errors. I did put on new tires shortly after the engine change, and run the same pressures as before. Same brand of tire.
Anyone have any ideas on how to get our old mpg back?
Thanks in advance!
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Does NOBODY have any clues as to why I'm losing 25% of my mpg?? At least a few possibilities would be helpful. My ideas are 1) clogged catalytic converter....(how do I determine) 2. Oxygen sensor issues (but no error codes?) 3. MAF sensor 4) problem with injector(s). Getting a replacement engine in California I don't believe would make a difference, since the basic engine is the same. But I DON'T KNOW, and it's a very expensive problem for someone who travels.
Help, please!
Help, please!
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
Some of the basic things in broad terms looked at, the most basic engine diagnostics, is cylinder compression, manifold vacuum, and valve timing. A mechanic's vacuum gauge can measure all three directly and indirectly. It will also identify any exhaust restriction very quickly and easily. They are inexpensive.
More modern engine diagnostics can infer things like cylinder compression without direct physical measurement, or having to remove sparkplugs &c, and test for other engine and ignition faults. Might try some of these basic tests and supplement them with a visit to shop that has the right diagnostic equipment, it shouldn't be that expensive. Sort of like an EKG machine for your engine. Maybe $75 or $100 something like that.
More modern engine diagnostics can infer things like cylinder compression without direct physical measurement, or having to remove sparkplugs &c, and test for other engine and ignition faults. Might try some of these basic tests and supplement them with a visit to shop that has the right diagnostic equipment, it shouldn't be that expensive. Sort of like an EKG machine for your engine. Maybe $75 or $100 something like that.
Fleet Mechanic
Joined: Nov 2011
Posts: 1,825
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From: Land of Taxes
X2 on the basic ECM/TCM diagnostics to look tor pending trouble codes. You need to have it hooked up to a computer with Ford software to see deeper troubles.
....also check air filter, fuel filter or look for a vac leak which would cause the O2s to call for a richer than needed mix.
Look at the MAF sensor. If its gunked up with smoockus it will cause AF mix problems.
What indications or troubleshooting dictated an engine replacement after <130K miles?
A gaser with regular service should easily do double that miles.
Read the plugs and tailpipe. Black=rich.
Did you get any warranty with the 10K engine rebuild? You'd think the installer would stand behind the work?
....also check air filter, fuel filter or look for a vac leak which would cause the O2s to call for a richer than needed mix.
Look at the MAF sensor. If its gunked up with smoockus it will cause AF mix problems.
What indications or troubleshooting dictated an engine replacement after <130K miles?
A gaser with regular service should easily do double that miles.
Read the plugs and tailpipe. Black=rich.
Did you get any warranty with the 10K engine rebuild? You'd think the installer would stand behind the work?
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Tedster9:
Thanks for responding!! Please be aware that I have a Bluetooth OBD tester (which shows no errors) and that it is a brand new engine installed by a Ford dealer. It runs silky smooth, without any errors coming up on the OBD tester. I just cleaned the MAF sensor, and will be replacing the air filter.
Thanks for responding!! Please be aware that I have a Bluetooth OBD tester (which shows no errors) and that it is a brand new engine installed by a Ford dealer. It runs silky smooth, without any errors coming up on the OBD tester. I just cleaned the MAF sensor, and will be replacing the air filter.
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X2 on the basic ECM/TCM diagnostics to look tor pending trouble codes. You need to have it hooked up to a computer with Ford software to see deeper troubles.
....also check air filter, fuel filter or look for a vac leak which would cause the O2s to call for a richer than needed mix.
Look at the MAF sensor. If its gunked up with smoockus it will cause AF mix problems.
What indications or troubleshooting dictated an engine replacement after <130K miles?
A gaser with regular service should easily do double that miles.
Read the plugs and tailpipe. Black=rich.
Did you get any warranty with the 10K engine rebuild? You'd think the installer would stand behind the work?
....also check air filter, fuel filter or look for a vac leak which would cause the O2s to call for a richer than needed mix.
Look at the MAF sensor. If its gunked up with smoockus it will cause AF mix problems.
What indications or troubleshooting dictated an engine replacement after <130K miles?
A gaser with regular service should easily do double that miles.
Read the plugs and tailpipe. Black=rich.
Did you get any warranty with the 10K engine rebuild? You'd think the installer would stand behind the work?
The old engine was showing a "check engine" light. After replacing all the coils 2X (once with Amazon cheapies and second time with Motorcraft) I still got a cyl. #4 misfire. Mechanic pulled plug....oily. Pressure check showed 70 psi.
I thought about just getting the heads done, but since we live in this and drive it as our primary vehicle daily, I needed 100% peace of mind so I sprung for the new (rebuilt) engine.
The work is warranteed by Ford. If the MAF sensor cleaning and air filter don't change anything, what next?
Thanks again!
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From: Home Base Nebraska
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Fleet Mechanic
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From: Southwest Ohio
Easiest way to test for increased back pressure in an exhaust is to pull the oxygen sensor (the sensor before the catalytic converter). Get yourself a pressure gauge and rig up an adapter that threads into the O2 sensor port (I bought my adapter at a hydraulic hose shop). Start the engine. There should be basically no pressure registering on the gauge. I've tested cars that registered 4-5 psi of back pressure at 3000 rpm. This test will tell you if you have a clog in your cat.
You can't expect anyone to magically provide you with THE answer to your problem. There are many things that can affect your fuel mileage. The only way to resolve your problem is proper diagnostics.
-- Dave
You can't expect anyone to magically provide you with THE answer to your problem. There are many things that can affect your fuel mileage. The only way to resolve your problem is proper diagnostics.
-- Dave
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From: Home Base Nebraska
Another thing to look at is the brand of fuel you are using I've found that something has changed and unless I use top tier gas from Shell, Exxon and so one I loose at least 1 mpg. The ones that I have found to be the worst are Pilot/Flying J, Sunoco any of the supermarket outlets.
Denny
Denny
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
Easiest way to test for increased back pressure in an exhaust is to pull the oxygen sensor (the sensor before the catalytic converter). Get yourself a pressure gauge and rig up an adapter that threads into the O2 sensor port (I bought my adapter at a hydraulic hose shop).
Fleet Mechanic
Joined: Nov 2011
Posts: 1,825
Likes: 43
From: Land of Taxes
Putting in new air filter today. Cleaned MAF sensor today. MAF wires looked OK, but cleaned anyway. Just checked....interior of tailpipe is sooty black.
The old engine was showing a "check engine" light. After replacing all the coils 2X (once with Amazon cheapies and second time with Motorcraft) I still got a cyl. #4 misfire. Mechanic pulled plug....oily. Pressure check showed 70 psi.
I thought about just getting the heads done, but since we live in this and drive it as our primary vehicle daily, I needed 100% peace of mind so I sprung for the new (rebuilt) engine.
The work is warranteed by Ford. If the MAF sensor cleaning and air filter don't change anything, what next?
Thanks again!
The old engine was showing a "check engine" light. After replacing all the coils 2X (once with Amazon cheapies and second time with Motorcraft) I still got a cyl. #4 misfire. Mechanic pulled plug....oily. Pressure check showed 70 psi.
I thought about just getting the heads done, but since we live in this and drive it as our primary vehicle daily, I needed 100% peace of mind so I sprung for the new (rebuilt) engine.
The work is warranteed by Ford. If the MAF sensor cleaning and air filter don't change anything, what next?
Thanks again!
What's next is a visit to a Ford dealer with this complaint.
Have the ECM & TCM read for any pending codes.
Once you have the engine broken-in after a few thousand miles add Prolong to the oil. I use Mobile 1 and Prolong. I use the 15K extended Mobil 1 and change it at about 10K.
I've seen prime power generators run with Prolong and organic oil with virtually no wear at recommended service teardowns. Up to and beyond 20,000 hours. Diesel and N. Gas.
I've been using Prolong for 25-30 years.
Change the trans fluid every 60K.
And you are welcome.
Do follow up if somethings found.
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Tedster9:
Thanks for responding!! Please be aware that I have a Bluetooth OBD tester (which shows no errors) and that it is a brand new engine installed by a Ford dealer. It runs silky smooth, without any errors coming up on the OBD tester. I just cleaned the MAF sensor, and will be replacing the air filter.
Thanks for responding!! Please be aware that I have a Bluetooth OBD tester (which shows no errors) and that it is a brand new engine installed by a Ford dealer. It runs silky smooth, without any errors coming up on the OBD tester. I just cleaned the MAF sensor, and will be replacing the air filter.
Putting in new air filter today. Cleaned MAF sensor today. MAF wires looked OK, but cleaned anyway. Just checked....interior of tailpipe is sooty black.
The old engine was showing a "check engine" light. After replacing all the coils 2X (once with Amazon cheapies and second time with Motorcraft) I still got a cyl. #4 misfire. Mechanic pulled plug....oily. Pressure check showed 70 psi.
I thought about just getting the heads done, but since we live in this and drive it as our primary vehicle daily, I needed 100% peace of mind so I sprung for the new (rebuilt) engine.
The work is warranteed by Ford. If the MAF sensor cleaning and air filter don't change anything, what next?
Thanks again!
The old engine was showing a "check engine" light. After replacing all the coils 2X (once with Amazon cheapies and second time with Motorcraft) I still got a cyl. #4 misfire. Mechanic pulled plug....oily. Pressure check showed 70 psi.
I thought about just getting the heads done, but since we live in this and drive it as our primary vehicle daily, I needed 100% peace of mind so I sprung for the new (rebuilt) engine.
The work is warranteed by Ford. If the MAF sensor cleaning and air filter don't change anything, what next?
Thanks again!
Was this a is a "brand new" or "rebuilt" engine?
If the old engine had misfires over a prolonged time period I would seriously suspect a clogged or partially clogged cat, dumping unburied fuel into the cat from misfires is the the quickest way to clog one up. The sooty tailpipe could be leftover from the old engines misfires. How does the engine feel performance wise?
And those new tires are the same exact size, correct?
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Was this a is a "brand new" or "rebuilt" engine?
If the old engine had misfires over a prolonged time period I would seriously suspect a clogged or partially clogged cat, dumping unburied fuel into the cat from misfires is the the quickest way to clog one up. The sooty tailpipe could be leftover from the old engines misfires. How does the engine feel performance wise?
And those new tires are the same exact size, correct?
If the old engine had misfires over a prolonged time period I would seriously suspect a clogged or partially clogged cat, dumping unburied fuel into the cat from misfires is the the quickest way to clog one up. The sooty tailpipe could be leftover from the old engines misfires. How does the engine feel performance wise?
And those new tires are the same exact size, correct?
RE: Vacuum vs pressure at catalytic converter.....What should I get for readings for vacuum at idle and at Oxygen sensor port?
I just recorded a 9.2 mpg, but that's just one fill up. I'll update this as I get more data.
Thanks again!