HELP!!! running lean and running rich at the same time! WTF?

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custom89stang

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#1

• Aug 7, 2005

• #1

so some of you know i've been having problems with a lean misfire. heres the story..... I have been having problems with a lean misfire from anywhere from idle to about 1700 RPMS, after that in the RPM band no lean misfires. So my mechanic disconnects and plugs the EGR, but that still doesn't do anything. He also see lots of black smoke coming from my exhaust and i told him i've been getting MORE normal than usual CRAPPY gas mileage. So what i have been told on here (before any of this info) was to replace EGR (just tried that so thats out of the picture), O2 sensors, Temp. sensor (which my mechanic says controls the fuel curve somewhat), and TPS sensor..... does anyone have ANY IDEAS?!? I think i'm gonna cry or just sell the 5.0 I LOVE SO MUCH.....this is too much B.S. (been having this problem for like 3 months without being able to fix it). I think tomorrow i'm going to the dealership to get new O2 sensors and a new temp sensor....SOMEONE PLEASE HELP I JUST WANT MY CAR TO RUN NORMALLY!!! So the main problems are: lean misfire popping early in the RPM Band, and running to rich ****ty gas mileage! I never thought i would see too lean and too rich problem on the same #@$%in car. Also i must mention the car lags and stutters in the early RPM's as well....when it misfires....if that means anything

 

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custom89stang

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#2

• Aug 7, 2005

• #2

bump anyone?

 

Mike86Stang

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#3

• Aug 7, 2005

• #3

IM me on AIM & i'll try & get it sorted out for you.

AIM is Mike86Stang

 

9T3SVT

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#4

• Aug 8, 2005

• #4

Clean your MAF wires

 

jrichker

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#5

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Dump the codes and see what the computer says is wrong…

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.

 

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custom89stang

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#6

• Aug 8, 2005

• #6

thanks 9t3svt but i already tried that

 

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custom89stang

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#7

• Aug 8, 2005

• #7

my mechanic told me icant dump the codes unless the check engine light is on and its NOT on

 

jrichker

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#8

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custom89stang said:

my mechanic told me icant dump the codes unless the check engine light is on and its NOT on

Click to expand...

To put it politely, he's wrong.

I would recommend that you find another mechanic or use my previous post and lean to do it yourself.

The codes can be dumped anytime the computer is functional. The check engine light does not need to be on. There are stored codes that will not always set the check engine light on.

 

Zero_chance

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#9

• Aug 8, 2005

• #9

Youre getting (or in theory you WOULD be getting) bad gas mileage if you are in fact running lean because when the O2s read lean the PCM tries to compensate by addding more fuel. That explains the ****ty gas mileage. Have you actually gotten a lean code yet or are you just listening to the exhaust?

 

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custom89stang

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#10

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im getting a lean misfire....jrichker i wish i could get another mechanic but he is very good, he has a supercharged 347 and he has a 2004 mystichrome cobra...so i know he knows what hes talking about. maybe he meant that it wouldnt be of any use (or its not that serious) unless the check engine light is on, so there would be no point in pulling codes

 

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custom89stang

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#11

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my mechanic listened to it and it makes a popping sound which my mechanic says is a lean misfire. so he told me too, an i just bought a new temp. sensor which was his recommendation. After that i think im gonna replace the 02's and if that doesnt work, TPS sensor, and if that doesnt work im gonna SELL MY CAR :-(

 

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custom89stang

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#12

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• #12

TOO CLARIFY: when i was over there the other day and he tried plugging the EGR valve, he said he noticed a lot of black smoke and that im running WAY too rich and i told him i'd been getting very crappy gas mileage...like i drive an hour and my car went from like half a tank to a quarter tank! INSANITY!....but like i said, my main concern is that i'm running to lean and too rich at the same time

 

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custom89stang

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#13

• Aug 8, 2005

• #13

zero_chance, thanks a lot i guess that makes a lot of sense....the main question is what is making my car run lean again? my mechanic tested for vacuum leaks and leaks all around the intake (after the MAF) and found nothing, thats why he said replace the temp. sensor

 

9T3SVT

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#14

• Aug 8, 2005

• #14

custom89stang said:

my mechanic listened to it and it makes a popping sound which my mechanic says is a lean misfire. so he told me too, an i just bought a new temp. sensor which was his recommendation. After that i think im gonna replace the 02's and if that doesnt work, TPS sensor, and if that doesnt work im gonna SELL MY CAR :-(

Click to expand...

Do not, I repeat, do not simply throw parts at it and hope you guessed right. You will waste time and money doing that. Do this instead, troubleshoot, diagnose, repair. I hate to say it but if your mechanic can't figure out what's wrong then he isn't as great as you think. Just because he owns 2 fast cars doesn't mean jack 5hit!! Most of the best mechanics I know own total buckets because they spend more time on everyone elses crap. Please read my third sentence over again and do it right the first time

 

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custom89stang

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#15

• Aug 8, 2005

• #15

thank you for the reply 9T3SVT i will take it too heart and if this new temp. sensor doesnt fix the problem probably end up pulling codes.

 

jrichker

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#16

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9T3SVT said:

Do not, I repeat, do not simply throw parts at it and hope you guessed right. You will waste time and money doing that. Do this instead, troubleshoot, diagnose, repair. I hate to say it but if your mechanic can't figure out what's wrong then he isn't as great as you think. Just because he owns 2 fast cars doesn't mean jack 5hit!! Most of the best mechanics I know own total buckets because they spend more time on everyone elses crap. Please read my third sentence over again and do it right the first time

Click to expand...

Well spoken! This is some of the best advice you'll get...

Go back and dump the codes. If you don't want to DIY, go to AutoZone or one of the other auto parts chains and they will do it for you. Just because the check engine light isn't on doesn't mean there isn't something that the computer set a code for that needs fixing. A 5 cent paper clip can get a lot of useful info out of the computer if you take the time to use it correctly.

 

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custom89stang

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#17

• Aug 8, 2005

• #17

lol, thanks for the tips! Off the top of your head is there anything that comes to mind that would make a 5.0 Run lean?

i mean besides what i've tried, vacuum leak, stuff after the MAF, EGR....