I have a 93 Dakota, 178K 5.2 V8, oil change every 2500 miles since 100K miles, and most of the time I start it up it feels like its missing for anywhere from 5 to 15 minutes on average. Sometimes it wont happen for weeks or longer. It has all new cap, rotor, plugs, plug wires, coil, completely rebuilt computer(if you want to call it that), it was also sent back and re-tested, I did try different injectors a while ago and still did it. Battery is new. I'm looking for ideas on what else to check. I don't believe the miss to be spark. I'm guessing lazy fuel injector if that's a thing. Iv pulled spark plug boots trying to identify which cylinder when the issue is occurring and all cylinders do the same thing. Iv also pulled the connector on the injectors but have not been able to identify which cylinder. When changing the plugs I lined them all up and they all looked the same. I'm hoping I'm not the only one that has ever experience this. When not missing it runs like a sewing machine. I'm stumped. The intermittency of this problem baffles me.

 

What brand/type of plugs did you install?

 

Autolite 3924

 

I'm no mechanic but kinda in the same boat as you. I have a 1993 FWD Caravan with all new ignition pieces including crank & cam sensors.
Same time I just installed a used engine and the car had a full tank of 2.5 year old fuel .... so naturally am fighting a few bugs.
One bug is the way it runs when cold .... It runs rough, the idle fluctuates, leaving a stop sign on a road with 55 mph speed limit I have noticed it popping back through the TB and the car bucks. ..... Something is seriously not happy. Once it warms up it runs perfect.

Just yesterday I noticed a vacuum line that got knocked loose on the TB, I plugged it back in. This morning when I started it up, it seems to be back to normal now with a steady smooth idle and no fluctuation.



As I said, I'm no mechanic so I'm not sure what that vacuum line operates ... Warmed up the motor runs smooth and could not hear a hiss like a vacuum leak .... there was no reason to suspect a vacuum leak. I have been flushing out the coolant system more days then I care to admit, and working with the hood open and engine running .... no indication of a vacuum leak. .... So I looked around inspecting the vacuum lines and also have another that has come loose. That one I have to raise the car on jack stands and get to it from underneath tomorrow.

So two disconnected vacuum lines and the car runs fine with no indication of vacuum leaks ...... I would not believe it myself except it just happened to me.
Just a suggestion to check your lines, especially on the TB. If you have a loose or leaking line .... it might do what you are talking about.

 

So I have narrowed this all down to two lazy injectors that are slow to fully start working after start up. A stethoscope with a rod on the end of it placed at the base of the injectors confirmed non working injectors after startup of in an intermittent pattern. I could hear them cutting in and out after start up. I will; be changing out the two problematic injustore to see if the issue lies in wiring or the injectors themselves.

 

If two of them are bad, replace ALL of them. They all live in the same environment, so if two have failed, you can bet that the rest aren't far behind.

 

Great advice. I plan to. Thank for your input.

 

Good catch, glad you found something off that can be corrected.
Small issues like this prompts me to use seafoam once a year in the fuel tank .... hoping it will clean the fuel system including injectors.

I have seen videos of people cleaning injectors .... remove them and connect to power and spray carb cleaner through them and achieve a nice spray pattern .... then re-install.

Everything wears out sooner or later and may just need replaced. ..... I'm starting to suspect I may have a random fuel issue. And a fuel injector causing issues .... driving for 2 hours today and randomly started to cut out ...... First time it happened I was worried maybe a bad "new" crank sensor ..... 2nd time, I'm thinking a fuel issue and a injector.

Life happens.

 

Iv been chasing this for quite a while. Wasn't much left to look at. But hearing the injector start and stop on and off again confirmed it. I only use the truck hunting once a year so in-between I end up saying "I'll get to it in the off season " but always found other things to work on. I'm not sure if it could still be wiring or whatever drives thes injectors but I guess I'l be finding out after a full replacement. I'm open to anyone's input to if there are better injectors than others i.e 3 hole vs 4 hole and which to stay away from i.e brand.

 

While it is always possible it is wiring .... I suspect it is not.
The truck sits a lot, the old fuel gets gummed up in it and the injectors get lazy .... once they get moving and functioning properly they work ..... I bet yours are just dirty and need cleaned.

Todays fuel has a short shelf life .... I watched this on my Uncle's 77 Dodge truck ..... The truck sat more then it was driven. It had 4-5 year old fuel in it .... he thought it was fine to add a few gallons of fresh fuel in it and drive it.


The carburetor was rebuilt a few months ago and failed again .... I took the carb apart and cleaned it .... It was full of a slime/gel that was coming from the tank.
Ran fine as long as I never connected the fuel tank to it .....
Are you sure you are running enough fuel through it to keep it clean?

You can replace the injectors, if you have bad fuel in the tank it will just continue to be a problem

I also want to add my Uncle's issue was more severe then yours possibly just cleaning the fuel system and running the tank dry and fresh fuel added with seafoam would be enough.
Things usually happen for a reason, if you have dirty injectors I want to clarify you have good fuel in the tank.