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1995 F150 Runs Rich

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Old 10-08-2011, 07:35 PM   #1
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Default 1995 F150 Runs Rich

My 1995 F150 4x4 5.8 L Runs Rich, you can smell fuel from tail pipe. I recently Replaced O2 Sensor. I'm getting Exhaust Leak at Manifold fixed on Monday, Plus a Complete new Exhaust system installed on the same day.
The only Mods to my 5.8L is a Hypertech Chip and a K&N Filter, other then this a Completely Stock Motor. A friend of mine suggested I run a couple of tanks of High Test (104 Octane) thru it, I did no change really! So why am I still having trouble with it running Rich and Rough at times? Could the Chip be causing Problems? Please any Help would be greatly appreciated!!!!!

Barky
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Old 10-08-2011, 08:46 PM   #2
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Eh, the non-OEM stuff is a concern, not so much for what they do when working right, but how to recognize and troubleshoot the process when things are wrong.

Have heard stories that the over-oiling the K&N filter will foul the mass-air flow (MAF) sensor. Or the MAF could simply be dirty - be sure to use the specific MAF cleaner - do not use carb cleaner!

No experience with the various chip offerings - can't help out there.

Another possibility is that the injectors are fouled - not atomizing the fuel fine enough. Seafoam is a favorite of many forum members, I also like Berryman's B12.
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Old 10-08-2011, 09:38 PM   #3
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An exhaust manifold leak could cause rich too. If more unburned air is getting into the system, which with a leak it can, it will think it's running lean
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Old 10-08-2011, 09:49 PM   #4
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If you didn't disconnect the battery when you changed the o2 sensor then the computer won't recognize the new one
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Old 10-09-2011, 09:31 AM   #5
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Quote:
Originally Posted by Barry McCockener View Post
If you didn't disconnect the battery when you changed the o2 sensor then the computer won't recognize the new one
I did Disconnect the battery before Install, I was told I should do that.
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Old 10-09-2011, 09:57 AM   #6
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Quote:
Originally Posted by wde3477 View Post
Eh, the non-OEM stuff is a concern, not so much for what they do when working right, but how to recognize and troubleshoot the process when things are wrong.

Have heard stories that the over-oiling the K&N filter will foul the mass-air flow (MAF) sensor. Or the MAF could simply be dirty - be sure to use the specific MAF cleaner - do not use carb cleaner!

No experience with the various chip offerings - can't help out there.

Another possibility is that the injectors are fouled - not atomizing the fuel fine enough. Seafoam is a favorite of many forum members, I also like Berryman's B12.
Any Idea where the MAF Sensor is located on a 1995 F150?
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Old 10-09-2011, 10:56 AM   #7
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You may want to get rid of the K&N oil bath air filter, even if only one drop of oil is used, as it may contaminate the MAF sensor again and generally will only cause problems with these sensors.

The MAF is between the throttle body and air filter, should be a 5 wire connector going to it if I remember correctly.

An engine that runs excessively rich can foul out O2 sensors over time, probably shouldn't keep running it like that longer than a few weeks at most.

Also, 87 octane is usually designed for low compression engines. It burns "cooler," longer and slower.
93 octane is usually designed for higher compression engines. It burns "hotter," shorter and quicker.

All Ford engines of this gen run between 8-9CR and require 87 only, anything higher is only compensating for pre-detonation or pre-ignition and will not burn for the entire stroke of the piston, making it less efficient.

Last edited by bluecar5556; 10-09-2011 at 12:05 PM.
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Old 10-09-2011, 01:17 PM   #8
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Quote:
Originally Posted by bluecar5556 View Post
You may want to get rid of the K&N oil bath air filter, even if only one drop of oil is used, as it may contaminate the MAF sensor again and generally will only cause problems with these sensors.

The MAF is between the throttle body and air filter, should be a 5 wire connector going to it if I remember correctly.

An engine that runs excessively rich can foul out O2 sensors over time, probably shouldn't keep running it like that longer than a few weeks at most.

Also, 87 octane is usually designed for low compression engines. It burns "cooler," longer and slower.
93 octane is usually designed for higher compression engines. It burns "hotter," shorter and quicker.

All Ford engines of this gen run between 8-9CR and require 87 only, anything higher is only compensating for pre-detonation or pre-ignition and will not burn for the entire stroke of the piston, making it less efficient.
Ok thanks will try going back to the OEM filters. A friend of mine suggested the Higher Octane for a tank or 2 to burn off excessive soiling of injectors..........
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Old 10-09-2011, 01:34 PM   #9
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Actually the higher the octane the slower it burns which is why higher octane is used to reduce detonation, allows more advanced timing, and will tolerate higher compression ratios. Many of the tuner kits depend on the use of higher octane fuels.
As stated above exhaust manifold leaks are a common cause of a rich mixture since it fools the O2 sensor. Once the leak is repaired reset the computer and see what happens.
regards
rikard
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Old 10-09-2011, 01:45 PM   #10
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Quote:
Originally Posted by rikard View Post
Actually the higher the octane the slower it burns which is why higher octane is used to reduce detonation, allows more advanced timing, and will tolerate higher compression ratios. Many of the tuner kits depend on the use of higher octane fuels.
As stated above exhaust manifold leaks are a common cause of a rich mixture since it fools the O2 sensor. Once the leak is repaired reset the computer and see what happens.
regards
rikard
You're right,
87 burns "cooler," longer and faster = lower compression engines
93 burns "hotter," shorter and slower = higher compression engines

Thanks for the up, rikard.

Last edited by bluecar5556; 10-09-2011 at 02:19 PM.
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