Burning a bit rich.
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Cargo Master
Joined: Nov 2003
Posts: 2,000
Likes: 39
From: North Dakota
Burning a bit rich.
So I have a 88 EFI 302 with an AOD. I have no CEL and am pulling no codes but I am running rich. If you put your finger in the end of my tail pipe it will come out jet black. And at idle the smell of exhaust is very present outside the vehicle. I never really looked for the reasoning before but with gas prices the way they are it has me wanting to fix it. What are some things I should be looking at?
Senior User
Joined: Feb 2004
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From: GOING BACK TO TEXAS!!!
are the plugs covered in black, or do they look normal. what kind of MPG are you getting? have you advanced your timing (about 12 degrees) from the stock ten degrees beacuse of your agressive ignition module? If you (or a PO) advanced your timing too much or retarded it too much, it will run rich because of the incomplete fuel burn. Just my two cents.
Posting Guru
Joined: Apr 2005
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From: Longview, TX
You may be far ahead of me. When replacing the timing chain I noticed the pointer for setting the timing is not quite up to space shuttle quality control. It has sloppy holes and is just a light piece of metal that may not be accurate. My point is set your timing until you get just a little knock up long hills then back the timing off just a hair.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Check the fuel pressure at the rail, and sniff the vacuum line that attaches to the FPR for gas, if fuel pressure is not 35 with vacuum and 43-45 without and/or there is gas in the vacuum line the FR is bad.
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Cargo Master
Joined: Nov 2003
Posts: 2,000
Likes: 39
From: North Dakota
I have replaced the fuel pressure regulator twice just to make sure I did not get a bad one. My timing is advanced to 12. As for my plugs they are new as well and I am getting right around 9 mpg in town. To make a long story short I put a 302 H.O. in my truck a couple of years ago because I blew the original. Even before I blew the factory engine it was burning rich. So it kind of has me stumped.
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FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
OK.. we need to go over all the detail then. What computer and wiring harness are you using? Are ALL the sensors connected and within range?
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Cargo Master
Joined: Nov 2003
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From: North Dakota
I have not altered the computer or wiring harness. They both work with the H.O. The only real difference with the H.O. engine is that it has a roller cam and a 351 firing order. I used the original truck intakes. I have gone through and tested sensors and replaced everyone I could find. From EGR, O2, FPR, TPS, knock sensor, temp sensor, oil sensor, ignition module. The only ones I have not replaced is the IAC and MAP. I am getting proper vacuum from the MAP and also the right range from both.
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
It sounds like the computer is running open loop all the time, but it shouldn't with all new or verified sensors. The other possibility is that you have a bad computer.. it's one of the few things that hasn't changed by the sounds of it.
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Cargo Master
Joined: Nov 2003
Posts: 2,000
Likes: 39
From: North Dakota
You know, that could be a possibility because the truck has burned rich since the day I bought it. Even with the previous engine. I have everything to do the mass-air swap but a new wiring harness. Maybe I will just break down and do the swap to get another computer in it.
Posting Guru
Joined: Nov 2004
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From: sunny fla sometimes windy
Are you sure your injectors are also firing in the ho mode? Are you positive the
injectors are all opening and closing properly, Ie not leaking or letting some dribble out.
How old is the fuel in it? IF it is getting close to 90 days it is going bad and could be up
around 160 octane and that is why it seems rich because you ain't burning all the fuel
and you will never make any power like that.
injectors are all opening and closing properly, Ie not leaking or letting some dribble out.
How old is the fuel in it? IF it is getting close to 90 days it is going bad and could be up
around 160 octane and that is why it seems rich because you ain't burning all the fuel
and you will never make any power like that.
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Cargo Master
Joined: Nov 2003
Posts: 2,000
Likes: 39
From: North Dakota
I put all new injectors in 5 months ago. My gas is only about 4 days old, it is my daily driver. The injectors are the same in a H.O. and the regular truck engine. If I had mass air it would be different.
Posting Guru
Joined: Apr 2005
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From: Longview, TX
kam, how frustrating. Just in case you have not seen what computers will fit...Ford Fuel Injection » EEC Program Codes