Missing and bucking 88 Ranger

[ltbenji]

Alright guys, got a 88 Ranger with the 2.3 4 cylinder

Tuesday night I topped off my gas tank and drove home and parked the truck
Wednesday morning I started it up and it was missing all the way to work

At first it idled fine, but over the few days it now misses occasionally at idle and is still really rough under any sort of throttle or power

I have replaced the distributor, ignition coil, rotor button, distributor cap, TPS, and the plugs and wires are just a couple of months old and I've put a bottle of techron in it
Replaced one of the two fuel filters and going to replace the other one tomorrow. Had the fuel pressure checked and it checked out ok

Next step is to check and clean the injectors, intake and throttle body, and check the compression.

Any ideas on where to go next or what else to try?

 

[ltbenji]

http://www.youtube.com/watch?v=bwIO90tEkk8&feature=youtu.be


This is the tach while maintaining the same speed and throttle position

 

[upnsmoke]

How was the fuel pressure checked and under what conditions? Under load or just sitting? I would put a vacuum gauge on it myself. Compression check never hurts, leakdown can be telling as well if you have the means to test it conveniently(supplied air pressure and gauges). Your truck doesn't have a MAP sensor, does it? Primary ignition is suspect as well, I would say. With that erratic an rpm, if the ignition module was the cause, there is a chance you would see it with an intermittent blinking of a timing light. Hopefully someone who knows more than me will chime in.

 

[ltbenji]

The ignition module was replaced at the same time as the distributor...

Ill find about how the fuel pressure was tested...

 

[Mark_88]

The erratic RPMs sounds like MAP sensor...and the bucking...but the bucking also could be your low pressure fuel pump (in tank) going south...

Get someone to pull codes if you don't know how...there are articles on this for Gen I Rangers all over the internet...and probably a few in the tech library...

Could also be a few other things but some of what you've done would have corrected it by now...

MAP sensor is my first guess....look on the firewall just to the left of the engine...should be a small black rectangular box with wires and a hose (vacuum line)...go to a junkyard and pick one up if you can...last time I priced a new one they were $120...

 

[ltbenji]

Alright, the truck was dropped off at a shop on Monday and they have been working on it this week.

Changed out the plugs and it turns out I had the wrong plugs. They had worked fine for a couple months. They were motorcraft platinums and the shop put the correct plugs in.

The shop tried new MAP and computer which made no difference

Also checked the fuel pressure while at idle and while going up the road and it checked out fine

The truck runs much better but still has a fairly frequent miss.
Occasionally at idle and while accelerating and always misses on deacceleration.

I just started and ran it in the shop but am going to go back tomorrow and see if they will let me drive it.

Any new ideas??

And Upinsmoke, I have a vacuum gauge on the truck and it's been fine

 

[Mark_88]

Wow...I haven't been able to see you tach video due to connectivity issues, but it seems like you've changed everything under the hood except the motor itself. That gets pretty expensive, especially the diagnostics.

I did the same thing to mine over a longer period of time. Unfortunately, I'm tapped out as far as new ideas go, but suspect something electrical like a faulty ground or sensor (like thee MAP, but you've tried that).

Can't see your last post, but were they able to check for codes?