Fuel economy problem
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4wd High
Joined: Oct 2015
Posts: 9
Likes: 0
Fuel economy problem
Hi all,
I have a 1989 Ford E350 motor home. It has the 460/7.5l engine. I was having a problem with cold idle which was way too rich and low when cold.
When it warmed up it was a little rich but ran better. The timing was out of specs and code reader indicated a problem with HO2S. But it would get about 11mpg and had enough power to handle the challenges on the road.
I replaced the O2 sensor and adjusted the timing and it idles beautifully still has power but the sun vacuum gauge now indicates that I am frequently running in the Poor Red zone for MPG. There are no other codes on the reader and no check engine lights. I did the engine timing test with the code reader and it came in at the specs listed 32degrees btdc.
What am I missing here? I wish I had left the poor idle alone because now I am only getting 7mpg. Any suggestions?
I have a 1989 Ford E350 motor home. It has the 460/7.5l engine. I was having a problem with cold idle which was way too rich and low when cold.
When it warmed up it was a little rich but ran better. The timing was out of specs and code reader indicated a problem with HO2S. But it would get about 11mpg and had enough power to handle the challenges on the road.
I replaced the O2 sensor and adjusted the timing and it idles beautifully still has power but the sun vacuum gauge now indicates that I am frequently running in the Poor Red zone for MPG. There are no other codes on the reader and no check engine lights. I did the engine timing test with the code reader and it came in at the specs listed 32degrees btdc.
What am I missing here? I wish I had left the poor idle alone because now I am only getting 7mpg. Any suggestions?
Thread Starter
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4wd High
Joined: Oct 2015
Posts: 9
Likes: 0
Update
I rechecked my timing and ran a new Key on engine off check and found a continuous memory code for 32 and 41 but it passed the KOEO test fine and the Timing check was perfectly within specs. I cleared the continuous memory codes and will recheck after I take it for it's next trip..
Super Moderator
Joined: Aug 2003
Posts: 25,479
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From: Isanti, MN
I'm not convinced there's anything wrong. The vacuum gauge simply indicates that your engine is working hard, which is very common when you're driving in windy conditions or pulling a hill. How did it do for fuel economy before these issues came up?
Fleet Owner
Joined: Aug 2010
Posts: 21,253
Likes: 1,656
From: Reynoldsburg, Ohio
That was my thought as well---cowabunga Batman that's a heap 'o advance BTDC. If that's the actual reading I'd be shocked some sort of detonation issues haven't caused other issues.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
It ain't 32 degrees BTDC no way no how. Starter will kickback at anything approaching 20 I'd think.
But best fuel economy and performance will be at the maximum possible ignition timing setting. Use the vacuum gauge to set timing as alternative to using a light.
But best fuel economy and performance will be at the maximum possible ignition timing setting. Use the vacuum gauge to set timing as alternative to using a light.
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Senior User
Joined: Mar 2015
Posts: 231
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From: Seligman, AZ
If I would've remembered I could've checked the manual that I have in the van to see what the timing should be, or at least comparable. But like tedster said you can use a vacuum gauge to find the best vacuum and that will generally be your best point for ignition timing and sometimes even better since most people will set it according to the manual and not what their particular engine likes.
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4wd High
Joined: Oct 2015
Posts: 9
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The timing is actually set at 10 degrees btdc with the spout pulled. When the spout is in place and I am running the timing test on the OBD I code reader it shows the required 32 degrees advance when the engine is running at 2500 rpm, Which is what the book says it should be. When I bought the motor home and drove it around the first 100 miles I was getting 11 mpg. The sun vacuum gauge was mostly in the normal range except when entering the freeway ramps and it seemed to have plenty of power. I started to check it over because of a poor cold idle. the first thing I found was the timing was advanced off the scale. I set the timing to the 10 degrees that the tag advised with the spout disconnected. there was no improvement in the idle so I bought a code reader and found a bad heated o2 sensor. I replaced that and now I get 7 mpg and the sun vacuum gauge spends most of the time in the poor milage range even when cruising.
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