Born Free Leap'n Lions RV Club

Low mpg
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Author:  tanksalot [ Wed Sep 11, 2019 4:00 pm ]
Post subject:  Low mpg

We have a 1999 Born Free 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!

Author:  whemme [ Wed Sep 11, 2019 5:28 pm ]
Post subject:  Re: Low mpg

Two possibilities.

1) Clean the sensor wires in your MAF (mass air flow) Sensor
2) Replace your problably 3 oxygen sensors

Author:  tanksalot [ Wed Sep 11, 2019 6:48 pm ]
Post subject:  Re: Low mpg

Thanks! I’ve got a can of MAF sensor cleaner with me, so that will be easy. Is oxygen sensor replacement an on-the-road DIY project?

Author:  whemme [ Thu Sep 12, 2019 11:38 am ]
Post subject:  Re: Low mpg

Well you will have to climb under the coach in order to replace oxygen sensors.

Author:  tanksalot [ Thu Sep 12, 2019 1:19 pm ]
Post subject:  Re: Low mpg

One thing I keep wondering is possibly backpressure from a partially-clogged catalytic converter. Your opinion?

Thanks in advance!

Author:  whemme [ Thu Sep 12, 2019 4:33 pm ]
Post subject:  Re: Low mpg

I suppose that is possible also. I cleaned my MAF sensor with the CRC cleaner but it didn't help. My BF has 125,000 miles on it now and new plugs and coils didn't return my mpg back to normal either. I will wait to hear back from you if installing new oxygen sensors fixes your low mpg problem.

Author:  bornnorm [ Sun Sep 15, 2019 5:39 pm ]
Post subject:  Re: Low mpg

Interesting Discussion. Where are the mass flow sensor wires that may require cleaning? Sounds like an easy try.

As posted in another thread, we just returned from our 8 month trip across the country and back. Unfortunately we had to replace the transmission in California. We drove 10,000 miles round trip and now have 83,000 miles on our 1993 Born Free and 3,000 miles on the new transmission.

Interestingly to me we averaged 10 mpg on the trip to Seattle, 9 mpg on the trip from Seattle to Los Angeles and 11.5 mpg with the new transmission. The only system change was the addition of a large transmission cooler, which probably did not effect the mpgs.

The only new problem we encountered on the way home from CA was the Rear ABS light coming on occasionally.

'Tanksalot', it would be nice if you included your BF model number in your post.

Author:  whemme [ Sun Sep 15, 2019 6:00 pm ]
Post subject:  Re: Low mpg

Well I know where the MAF sensor is located on the Ford V10 powered Born Free models but I don't know what chassis you have. Is it a Ford 460 V8? Generally the MAF is located in the air intake system right after the air filter.

Author:  bornnorm [ Sun Sep 15, 2019 6:07 pm ]
Post subject:  Re: Low mpg

Yes it's the 460. I parked it in the front yard yesterday when we returned so I could give it a good cleaning before moving it to storage.

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