Hi everyone I have a problem. I have a 1990 LX 5.0 H.O with a AOD and it has a hard miss on one of the cylinders. it only does it when it is in 3rd or overdrive. it also some times "hopps" down the road and once it reaches temperature it occasonaly stalls out when at a light. I have replaced plugs wires rotor button and cap. it has no moddifications at all and I have been stumped for a while on it. the car has 105689 miles logged. the items I listed were replaced 3 months ago. and with OE Motorcraft parts. please help if you have any ideas.

 

Do you know if the misfire is always with the same cyl? Important to know that because certain things can cause a misfire and depending on if it is one or more or certain cyls.
Was this problem present before changing the plugs ,wires etc ?
Sometimes a coil can breakdown internally when under load and result in a misfire condition.
Always a good move to check and confirm good connections to the vehicle computer.
It never hurts to make sure the battery cable connections are CLEAN and tight. It may start OK and still have trouble providing the necessary power to keep the engine controls functioning correctly. Suppose we start with these checks and go from there.

 

it only started when the weather got cold and for some reason never lights the MIL on my cluster which I know works.... I also don't know where the ECM is on my car. there is a black box on the fire wall right behind the upper plenum. the box has a single large conector on it but nothing else...... the car is also a early 90 model so I am stumped.

 

If the ignition coil is original It would be a good move to replace it. They are not that expensive. There have been problems with older Ford distributors and replacement usually got rid of quite few misfire problems. Some parts are affected by temperature and it would not be smart for me to suggest replacing a lot of components without confirming whether they are defective or not. The two items above were the first to come to mind and before suggesting anything else some quality testing should be done to confirm if any other components are malfunctioning.

 

The car has 14 degree timing advance and I thought it might be water in the fuel. It also has been very cold. Most days are only 10 degree highs. The coil I plan to replace. I will post a picture of the engine and car I have no idea where the ECM is. It also is a non California emissions vehicle.

 

The wires in the picture are the old ones. They got replaced a while back. About 3 months ago.