Not getting fire to all the spark plugs

Tiny
RAYLEPKOWICZ
  • MEMBER
  • 1992 FORD MUSTANG
  • 100,000 MILES
2.3L 4cyl. Rebuilt top half. Motor runs but has no power when driving. I checked to see if I was getting a spark at the coil pak (this one has double coil packs). I am not getting spark at all 4 cylinders on either coil pack. The parts store recommended I change the crank position sensor, and I did but it still has the same problem. This is wierd, I even tried changing one coil pack and it ran great for about 3 miles down the road and then it went back to running bad again.
Thursday, August 25th, 2011 AT 10:26 PM

9 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
You can't let parts stores diagnose. They are only trained to sell parts. I have seen this before and it's usually caused by a bad Ignition Control Module.
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Thursday, August 25th, 2011 AT 10:54 PM
Tiny
RAYLEPKOWICZ
  • MEMBER
  • 9 POSTS
I changed the Ingnition control module, the car started right up. However the idle went up to around 2000rpm then settled down to around 1200. I adjusted the idle down to 1000 and took it out for a ride. When I would come to a stop the idle dropped to 500. When I got back the idle was only around 800 in park. I turned it off and restarted, the idle went up to 2000 and then dropped to 1200 again.
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Monday, August 29th, 2011 AT 10:56 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
You adjusted the idle? The idle is computer controlled and not adjustable and you shouldn't have been messing with the stop screws. Disconnect the battery for 10 minutes and restart it. It will then relearn the idle strategy but it may not be able to if you screwed up the base idle adjustment. There is a specific procedure for setting that up and it should never be touched.
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Monday, August 29th, 2011 AT 11:10 PM
Tiny
RAYLEPKOWICZ
  • MEMBER
  • 9 POSTS
I did just as you advised. There still seems to be a problem where the idle will start up fine and then somewhere after warming up it will drop down and act like it is misfiring. I noticed this most often when you come to a stop the idle drops too far and the engine hesitates.
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Wednesday, August 31st, 2011 AT 11:11 PM
Tiny
WRENCHTECH
  • MECHANIC
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I didn't advise you to adjust any idle.

You may have a bad IAC ( idle air control) but try eliminating any vacuum leaks and cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.
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Wednesday, August 31st, 2011 AT 11:18 PM
Tiny
RAYLEPKOWICZ
  • MEMBER
  • 9 POSTS
I'm sorry, let me clarify, I disconnected the battery waited 10 minutes and then reconnected to let the idle stablize. Definately will leave that idle screw alone. Thanks for the additional help, I will try cleaning the throttle body as you suggested and check for vacummn leaks and hopefully that will do it, if not I'll replace the IAC. Thanks again your help is very much appreciated.
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Wednesday, August 31st, 2011 AT 11:34 PM
Tiny
WRENCHTECH
  • MECHANIC
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When you disconnect the battery, what you have done is to erase all the adaptive memory in the computer. Now it will have to relearn the idle strategy so some early stalling may be normal. It would be a good idea after you have cleaned the throttle body. Just give it a chance to learn again.
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Wednesday, August 31st, 2011 AT 11:38 PM
Tiny
RAYLEPKOWICZ
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  • 9 POSTS
After cleaning the throttle body the engine ran as smooth as new. Took it out it ran great. The rpm settles around 1800 in neutral and 1400 in drive. I did not know what was normal for this car so I just left things alone and figured it would relearn with time. Thanks again for the help.
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Friday, September 2nd, 2011 AT 12:23 AM
Tiny
WRENCHTECH
  • MECHANIC
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Glad you got it resolved.
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Friday, September 2nd, 2011 AT 12:25 AM

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