Rough idle, check engine light on, black soot - Ford Forum - Enthusiast Forums for Ford Owners

Thread Tools Search this Thread
Old 04-22-2005, 12:04 AM
Thread Starter
Join Date: Apr 2005
Posts: 3
Default Rough idle, check engine light on, black soot

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
Reply With Quote
Old 04-22-2005, 02:57 AM
Join Date: Feb 2005
Posts: 61
Default RE: Rough idle, check engine light on, black soot

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.
Reply With Quote
Old 04-22-2005, 07:57 AM
Thread Starter
Join Date: Apr 2005
Posts: 3
Default RE: Rough idle, check engine light on, black soot

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!
Reply With Quote
Old 04-22-2005, 08:02 AM
Thread Starter
Join Date: Apr 2005
Posts: 3
Default RE: Rough idle, check engine light on, black soot

Is there a way to check the MAF sensor with a volt meter?
Reply With Quote
Old 07-14-2005, 12:09 AM
Join Date: Jul 2005
Posts: 1
Default RE: Rough idle, check engine light on, black soot

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,

Reply With Quote
Old 07-14-2005, 03:03 PM
Join Date: May 2005
Posts: 298
Default RE: Rough idle, check engine light on, black soot

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.
Reply With Quote
Old 07-15-2005, 01:49 AM
Join Date: Jul 2005
Posts: 608
Default RE: Rough idle, check engine light on, black soot

yep thats the quick an easy , un bolt the cats an test drive if it runs like a bat outta [email protected], you got bad cats , REMEMBER ITS GOING TO BE REAL LOUD << MAY NOT WANT TO DO ON A SUNDAY MORNING
Reply With Quote
Old 03-16-2010, 12:22 PM
Junior Member
Join Date: Mar 2010
Location: Warminster, PA
Posts: 2
Default Check Engine light, rough running and flat when accellerating

This morning my 08 edge, 6100miles started agitating while driving slow, it was more noticable. Then the check engin light came on. I have noticed the last few days that when I press the gas from being stopped it seems flat. I made appointment, svc tech said it was fine to drive around like that as long as the light is not blinking...What?
Reply With Quote
Old 03-18-2010, 04:44 PM
Senior Member
Join Date: Jan 2010
Location: Fresno, CA
Posts: 143

dont forget to rule out the IAC....clean the MAF filaments

I have posted a few times regarding IAC issues....just do a search on my posts...
Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
5.8L Crank it up, runs rough, jumps, shirks, soot out talipipe, unplug cyl. 3 runs better?? SAMF Ford F-250 & Ford F-350 2 12-08-2016 05:41 PM
Black soot in tailpipe Hipermiler139 General Tech 0 07-09-2012 12:57 PM
engine light/vibration/rough idle 98 expd avitasco Ford Expedition 5 06-18-2007 09:23 AM
1990 ranger engine light rough idle toddb Ford Ranger 10 10-10-2006 03:23 PM
1988 E150 5.0L idle problems and check engine light is on hdvespa Ford Econoline E Series 1 04-21-2006 04:23 PM

1993, au, check, engine, explorer, falcon, ford, idle, light, ranger, rough, rpm, running, runs, speed, start

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 02:23 AM.