Rough idle, check engine light on, black soot

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Rough idle, check engine light on, black soot

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Ford Forum >> Ford Trucks, Ford Vans & Ford SUV's >> Ford Explorer >> Rough idle, check engine light on, black soot

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Rough idle, check engine light on, black soot - 4/21/2005 10:04:11 PM

93redxlt

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My 93 XLT started running rough about a month ago. Upon start up the engine idle would surge up and down and almost die, then rev to about 1600 RPM, then almost die again. This would last a couple of minutes and then it would seem to stop after the engine warmed up. This was not every day, just every third day or so. About a week ago, the check engine light started coming on, and the engine has no power when first starting out. It seems to be fine at cruise and highway speed, but is most noticeable coming off of idle...just goes flat. A little scary pulling out into traffic. The check engine light will go off then come back on, sometimes at idle and sometimes at cruise. I borrowed a friend's code scanner. I get zero hard faults during the KOEO test, but do have code 157 (MAF sensor below minimum voltage)in the memory and once got a code 158 (MAF sensor above maximum voltage), but that hasn't come back. I ran the KOER tests several times and would sometimes get a 412 code (Unable to controlRPM during high RPM Self-test) and a 536 code (Brake on/off (BOO) circuit failure/not activated during the KOER) I was trying to determine if I was testing wrong, and was able to get the 412 code to go away, but never could get the 536 code to not show. After resetting the engine light, it will almost immediately come back on. Also, the exhaust stinks something fierce, and is producing a lot of black soot, which tells me rich. Shouldn't I be getting a hard fault code if the light keeps coming on? Another thing. My wife drove our Explorer on the freeway, and on two occasions she heard and felt a large bang from under the truck, as though the tranny was doing something violent. Could the computer sending a wrong signal to the tranny cause this? Maybe this isn't even related? If any of what I have described sound familiar or if you know what my problem or problems might be, PLEASE HELP!!!!!!!! THANK YOU!! Dave

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RE: Rough idle, check engine light on, black soot - 4/22/2005 12:57:12 AM

truckpuller

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The 536 code is due to you not pushing on the brake pedal during your test. Mass air flow sensor(MAF) can cause rich running conditios and black smoke cause it may be throwing a false reading to the computer which maybe telling it to run rich another thing is also a ECT engine coolant sensor will cause this also which will tell the computer if the engine is hot or cold and also may want to check catalytic convertor to see if its plugged up.

(in reply to 93redxlt)

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RE: Rough idle, check engine light on, black soot - 4/22/2005 5:57:46 AM

93redxlt

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Shouldn't I still be showing a hard fault, or do the faults clear as soon as the light goes out? What is the easiest way to check if my cat is plugged? Thanks!

(in reply to 93redxlt)

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RE: Rough idle, check engine light on, black soot - 4/22/2005 6:02:12 AM

93redxlt

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Is there a way to check the MAF sensor with a volt meter?

(in reply to 93redxlt)

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RE: Rough idle, check engine light on, black soot - 7/13/2005 10:09:37 PM

gkeith

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Hi All,

I am new to these forums so forgive me for reviving an aged post, but it seems to match the problem I am experiencing.

The vehicle is a 1993 Ford Ranger XL - 3.0L V6.

I pulled the codes:

KOEO - 111 (This Is Good)

CM - 157 (Mass Air Flow Sensor below minimum voltage), 158 (Mass Air Flow Sensor above maximum voltage)

KOER - 536, 538 (Both of these codes were indeed operator error)

The truck has a substancial lack of power, especially on acceleration. I took it to a tune up clinic, who promptly referred me to an exaust shop for possible plugged CATS. Exaust shop told me that the temp after the CATS was normal and probably they were OK and flowing fine. Went back to the tune up shop, they checked everything, could not find a thing in the ignition/distributor or anywhere. They still think it's the CATS, but the CATS are $300+ to replace, what if their wrong?

Possible Solutions:

The exaust shop is wrong and I should replace the CATS like the Tune Up Shop suggests. What is your opinion?

I have heard of some power loss due to a bad MAF (Mass Air Flow Sensor), but this bad??? What is your opinion?

Or... Maybe you know the silver bullet and it's none of the above. If so... Tell me now!

Thanks in advance for any help,

GKeith

< Message edited by gkeith -- 7/13/2005 10:17:11 PM >

(in reply to 93redxlt)

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RE: Rough idle, check engine light on, black soot - 7/14/2005 1:03:51 PM

hockeyhitman69

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it sounds like a mass air flow problem but it could be the converters if it were me i would disconnect them from the manifold and run the vehicle if you have lots of power after disconnecting them then you know your cats are the problem.

(in reply to gkeith)

Post #: 6

RE: Rough idle, check engine light on, black soot - 7/14/2005 11:49:49 PM

Ramrod48

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yep thats the quick an easy , un bolt the cats an test drive if it runs like a bat outta h@ll, you got bad cats , REMEMBER ITS GOING TO BE REAL LOUD << MAY NOT WANT TO DO ON A SUNDAY MORNING

(in reply to hockeyhitman69)

Post #: 7