I have tried everything I know of. Help!

[Trevorrudai]

Howdy. Been chasing an absolutely awful rough idle/misfire. I'll just list everything I know I've covered if you have any other ideas plz let me know thanks everyone.
Fuel pumps/pressure.
Fuel filter
Fuel pressure regulator
Spark plugs
Wires
Distributor
Rotor
Air filter
IAC
TPS
EGR/EVR
VACUUME HOSES
Throttle body

 

[RonD]

1986 2.9l Ranger?

Does it misfire when cold or more after it's warmed up?

What about at steady driving speed, is it misfiring?

I would do a compression test just to take it off the table or to find out if its the issue

Also you should have a timing light
After engine is warmed up and idling test each spark plug wire with timing light to see if you get a steady pulse

 

[Terry]

Have you checked the codes? If you have not you are throwing money at the wall. Most of the parts you have changed would not cause a misfire. Most fuel issues don't cause misfires. I would check the ignition control module.

 

[franklin2]

Howdy. Been chasing an absolutely awful rough idle/misfire. I'll just list everything I know I've covered if you have any other ideas plz let me know thanks everyone.
Fuel pumps/pressure.
Fuel filter
Fuel pressure regulator
Spark plugs
Wires
Distributor
Rotor
Air filter
IAC
TPS
EGR/EVR
VACUUME HOSES
Throttle body

I didn't have a missfire in my 2.9 (no putt putt in the exhaust) but I always had a rough idle. I will add to your list;

Reman computer
New injectors
new cylinder heads
new engine temp sensor
couple of ignition modules
no codes

Never did fix it. Some of the stuff I replaced for other reasons, but the rough idle never went away. I believe I determined over time and smelling the exhaust, that is was running a little rich at idle. If I let a little air into the engine somewhere, it would smooth right out. But the computer never liked the high idle that I was left with when doing that. All you had to do was slip the clutch a little when taking off from a stop and it never gave any trouble, drove it that way for years, and it ran really good with a lot of power. But always had that pesky rough idle.

 

[Trevorrudai]

It misfires more dramatically warmed up, but nonetheless also misfires cold. Also misfires during initial ignition of motor. As well as steady driving speeds it consistently misfires the entire time the motor is running. Checked compression within last 30 days all 6 cylinders pushing about 140.
Plan on checking timing today after work. My fuse panel was altered by one of the previous owners there is no conductive metal retainers in the fuse slot that the fuse is being held in by for my OBD reader, going to have to straight wire it in somewhere asap. Brand new ICM module also, and coolant temperature sensor. Upon disconnecting wires while engine running, many cylinders unhooked made very little change at all, cylinder 2 was quite dramatic, checked plug and was fouled, but correct gap, cleaned up nice so installed back into cylinder, inspected all other plugs and wires visually which appeared ok

 

[91stranger]

1986 2.9l Ranger

Ahh there's the problem... Get rid of the 2.9 and you won't have these issues lol. Actually them old distributors can be real finicky if they aren't installed properly. Sounds like something is off...… What brand distributor did you get?

 

[Bgunner]

Upon disconnecting wires while engine running, many cylinders unhooked made very little change at all, cylinder 2 was quite dramatic, checked plug and was fouled, but correct gap, cleaned up nice so installed back into cylinder, inspected all other plugs and wires visually which appeared ok

When pulling plug wire while running each should make a dramatic change, causing a misfire on that cylinder. So if this information is correct that most wires didn't make a difference then I would look in and under the distributer cap for signs of the spark traveling to either a different plug or to ground down the side of the cap.

 

[RonD]

Double, then triple check, firing order on the cap, info here: https://www.ford-trucks.com/forums/attachment.php?attachmentid=8616&stc=1&d=1204731360

Compression of 140psi average is lower but OK shouldn't cause misfires cold or warm

Yes, check the timing, and also check if there is a steady spark pulse at each spark plug

 

[franklin2]

I had a random rough idle. If you have actual dead cylinders, you should be able to find what's causing that. Don't give up.

I will tell you the sparkplug wires can be delicate. It's very easy to pull on them the wrong way and break that little nylon string with the carbon in it, or pull it out of the terminal in the boot. You may want to take your wires off and ohm them out while you wiggle them around and see if they are ok.

 

[rusty ol ranger]

Could also be bad injectors....

 

[Trevorrudai]

Last night I checked the resistance in all wires which all checked out ok. Also checked each spark plugs for consistent spark pulse which also checked out ok. While doing these tests I also hooked a sun tachometer to the coil to test for cylinder power balance. It calls to disconnect each wire, one at a time, from the spark plug and ground it to the engine, then record the RPMS. All wires except 2 & 4 remained at the 900 rpm idle I had it set to run at, when disconnected from the plug and grounded. 2 & 4 both dropped idle down 100 rpms to 800 upon being disconnected and grounded. Does this diagnose anything specific or more tests need ran? I have the sun tune up kit which allows me to also do the compression test, timing light adjust/record, vacuum gauge, and remote start.

 

[rusty ol ranger]

@RonD

Im totally pissing in the dark here but i have never heard of that test.

If you pull a plug wire its normal for RPMs to drop, so i would think that would be normal?

If compression is good and spark is good all youre left with is fuel delivery.

How does the plugs look?

 

[franklin2]

Last night I checked the resistance in all wires which all checked out ok. Also checked each spark plugs for consistent spark pulse which also checked out ok. While doing these tests I also hooked a sun tachometer to the coil to test for cylinder power balance. It calls to disconnect each wire, one at a time, from the spark plug and ground it to the engine, then record the RPMS. All wires except 2 & 4 remained at the 900 rpm idle I had it set to run at, when disconnected from the plug and grounded. 2 & 4 both dropped idle down 100 rpms to 800 upon being disconnected and grounded. Does this diagnose anything specific or more tests need ran? I have the sun tune up kit which allows me to also do the compression test, timing light adjust/record, vacuum gauge, and remote start.

That test means cylinders 1,3,5 and 6 are dead correct? If they make no difference in how it runs, then they are not firing. Hard to believe it will run on only cylinders 2 and 4.

 

[91stranger]

That test means cylinders 1,3,5 and 6 are dead correct? If they make no difference in how it runs, then they are not firing. Hard to believe it will run on only cylinders 2 and 4.

Umm... Wouldn't this make sense since your original complaint was rough idle?? Sounds like you got it figured out.

 

[rusty ol ranger]

It wouldnt even start on 2 cylinders.