[dfuller0227]

My 97 5.4 expedition is misfiring on #1 I have changed the spark plug, coil, and the fuel injector and also put seaform in side of my tank and #1 is still misfiring and only #1 what else could be the problem ?

[TxGreaseMonkey]

Engine Misfires

Most common engine misfires can be solved by:

1. Replacing platinum spark plugs with the exact ones (same brand and part no.) that came in the vehicle and ensuring they are properly gapped. If the vehicle came with single platinum plugs, changing them to double or quadruple platinum plugs can cause misfires, particularly if the gap is different. Therefore, I recommend using single platinum plugs and changing them every 50,000 miles. On FWD V-6 engines, be sure to change the rear plugs, despite the hassle.

2. Applying dielectric grease to the spark plug's porcelein and electrode.

3. Changing coils and coil packs, if changing spark plugs did not solve the problem. Bench testing coils is not reliable, since most break down under load (heat). Therefore, be sure to change coils and coil packs every 120,000 miles or 10 years, whichever comes first. Apply dielectric grease to terminals.

4. Replacing Ignition Control Module (ICM). These problematic components should be replaced every 120,000 miles or 10 years, whichever comes first. Bench testing ICMs is not reliable, since most break down under load.

5. Ensuring coil-on-plugs are squarely centered on the plug's electrode.

6. Changing spark plug wires every 80,000 miles. Regularly, wipe down plug wires with silicone spray, being very careful to keep it away from oxygen sensors.

7. Checking for pending codes that did not trigger the Check Engine Light.

8. Checking engine compression and looking for intake manifold leaks, in extreme cases.

[dfuller0227]

Engine Misfires

Most common engine misfires can be solved by:

1. Replacing platinum spark plugs with the exact ones (same brand and part no.) that came in the vehicle and ensuring they are properly gapped. If the vehicle came with single platinum plugs, changing them to double or quadruple platinum plugs can cause misfires, particularly if the gap is different. Therefore, I recommend using single platinum plugs and changing them every 50,000 miles. On FWD V-6 engines, be sure to change the rear plugs, despite the hassle.

2. Applying dielectric grease to the spark plug's porcelein and electrode.

3. Changing coils and coil packs, if changing spark plugs did not solve the problem. Bench testing coils is not reliable, since most break down under load (heat). Therefore, be sure to change coils and coil packs every 120,000 miles or 10 years, whichever comes first. Apply dielectric grease to terminals.

4. Replacing Ignition Control Module (ICM). These problematic components should be replaced every 120,000 miles or 10 years, whichever comes first. Bench testing ICMs is not reliable, since most break down under load.

5. Ensuring coil-on-plugs are squarely centered on the plug's electrode.

6. Changing spark plug wires every 80,000 miles. Regularly, wipe down plug wires with silicone spray, being very careful to keep it away from oxygen sensors.

7. Checking for pending codes that did not trigger the Check Engine Light.

8. Checking engine compression and looking for intake manifold leaks, in extreme cases.

Well this weekend I will change all the spark plugs to the original ones and the coils and ill let you know what happens thanks

[TxGreaseMonkey]

It's not uncommon for upper intake manifold (UIM) gaskets needing to be replaced on older vehicles. Try this if all else fails. I would go with Motorcraft spark plugs, gapped to spec.

[dfuller0227]

It's not uncommon for upper intake manifold (UIM) gaskets needing to be replaced on older vehicles. Try this if all else fails. I would go with Motorcraft spark plugs, gapped to spec.

The spark plugs was the problem I just bought those plugs like 2 weeks ago there where bosh platinum plugs but I changed them to the motorcraft and now its riding normal thanks.

[TxGreaseMonkey]

Not surprised. Always stick with the exact plugs that came in the vehicle. Personally, I stay far away from Bosch spark plugs and oxygen sensors. To a large extent, engineers design an engine around the spark plugs; therefore, the choice of plugs is more important than most people realize.

[dfuller0227]

Not surprised. Always stick with the exact plugs that came in the vehicle. Personally, I stay far away from Bosch spark plugs and oxygen sensors. To a large extent, engineers design an engine around the spark plugs; therefore, the choice of plugs is more important than most people realize.

I changed the spark plugs 2 days ago and everything was good but today when I pull up to a stop sign or light while the air conditioner was on the truck was jumping like it was.misfiring or something but if I put the truck in park while the air is on the truck runs normal and if I cut the air off the truck runs normal what is wrong is there something else I need to change besides the plugs ?

[smearcase]

Have you ruled out this item on TxGM's list? Check in dark for arcing.
" Changing spark plug wires every 80,000 miles. Regularly, wipe down plug wires with silicone spray, being very careful to keep it away from oxygen sensors. "

[TxGreaseMonkey]

I agree that spark plug wires should be changed every 80,000 miles, unless they are coil-on-plug wires. Wiping wires down with silicone spray is a must. Also, I would lightly coat the porcelein portion of the plug, and electrode, with dielectric grease. This helps prevent misfires and makes it easier to remove spark plug boots. Ditto for coating spark plug wire ends with dielectric grease that plug into coils, which you want to ensure are fully seated.

[dfuller0227]

I agree that spark plug wires should be changed every 80,000 miles, unless they are coil-on-plug wires. Wiping wires down with silicone spray is a must. Also, I would lightly coat the porcelein portion of the plug, and electrode, with dielectric grease. This helps prevent misfires and makes it easier to remove spark plug boots. Ditto for coating spark plug wire ends with dielectric grease that plug into coils, which you want to ensure are fully seated.

I did put dielectric grease on all of the plugs but I didn't spray silicon. I have coils on the truck do I need to spray silicon inside of each coil boot ?

[TxGreaseMonkey]

Since you coated the plugs with dielectric grease, and since you have coil-on-plugs, there's no need to do anything else. Just ensure each coil-on-plug boot is positioned directly over each plug.

[TxGreaseMonkey]

Hard to tell, from afar, what the problem is. I would clean the throttle body and throttle plate. Afterwards, clean the air box and replace the air filter. You may also have a bad MAF Sensor. If you replace it, only install a new sensor. Remanufactured MAF Sensors are horrible and are to be avoided. I would also check the Idle Air Control Valve. It may be bad and not increasing idle rpm, when the A/C is on.

[dfuller0227]

Hard to tell, from afar, what the problem is. I would clean the throttle body and throttle plate. Afterwards, clean the air box and replace the air filter. You may also have a bad MAF Sensor. If you replace it, only install a new sensor. Remanufactured MAF Sensors are horrible and are to be avoided. I would also check the Idle Air Control Valve. It may be bad and not increasing idle rpm, when the A/C is on.

Ok I will change the sensor, valve, filter and clean the throttle body this weekend and I will let you know what happens.