1997 with 4.0 runs good for awhile then starts smothering out and eventually quits. After sitting a couple minutes, it will usually start up and run fine for a few miles. Replaced entire EVAP system, fuel pump, coil pack.It's not throwing any codes and this has been going on for months. Sometimes it runs great for a week before acting up again, sometimes does it immediately after restarting. I think there's a "ghost in the machine". I love my truck but am getting frustrated to the point of getting rid of it! Can any one help?

 

Have you changed the Crankshaft Positioning Sensor? If so computer or wiring harness issue, possibly. Find out what you're missing in the equation: spark, fuel or compression.

Compression issues are usually problems that will exist consistently, so it is probably not that.

Spark and Fuel can be intermittent if an electrical component is failing or if there is an inconsistent signal transmitted or produced by the computer.

 

Does it do this during idle, or just whenever? What happens when you give it gas while it's dying?

 

It does it intermittently whether driving at speed or idling although I figured out how to make it do this anytime by getting on the brakes hard. I changed the brake booster but didn't help, it will still do this with the booster unhooked. I guess I'll try the crankshaft positioning sensor next.

 

It does this anytime whether idling or driving. If you give it gas it just quits sooner.

 

unplug the MAF and see if it runs any different.

 

It's been in the shop for over a week and they're saying they can't find anything wrong even though it still does the same thing, I'll get back with you if I don't get any results there. Thank you so much.Brian

 

Not sure about the style of exhaust converter you may have but it sounds like the old style that would plug up or you may have a vacuum leak.

 

If it dies when you hit the brakes, I would say you probably have a vacuum leak somewhere. You can look for leaks by spraying carb cleaner near all the vacuum lines/pcv/intake, and listening for a change in engine sound. For safety sake do this on a cold engine, and have a fire extinguisher ready... just in case. Disclaimer: Myself, or Ranger-Forums don't take any responsibility if you catch something on fire

I had a pretty bad vacuum leak on my truck, and found/fixed everything like this.