1999 Ranger XLT 4.0 Misfire/rough

[jhknight56072]

Ongoing issues with my 4.0. Often starts cold in winter on 4 or 5 cylinders. but no code, no fix.
Recently started a severe lurch/shudder around 40 mph or less, usually lower rpm. varies, but usually I stand on it and downshift at 5000rpm gets smooth again.
Sometimes starts with strong fuel odor. The other day barely started, and ran rough as hell, ... take it to a mechanic and it runs perfectly.
NO CHECK ENGINE LIGHT, and NO CODES. And the mechanics don't have a clue what to look at without codes.
Intermittent condition.
This ranger has new fuel pump, new plugs and wires. 176,000 miles on it.
Any ideas?
Thanks!

 

[rusty ol ranger]

Ongoing issues with my 4.0. Often starts cold in winter on 4 or 5 cylinders. but no code, no fix.
Recently started a severe lurch/shudder around 40 mph or less, usually lower rpm. varies, but usually I stand on it and downshift at 5000rpm gets smooth again.
Sometimes starts with strong fuel odor. The other day barely started, and ran rough as hell, ... take it to a mechanic and it runs perfectly.
NO CHECK ENGINE LIGHT, and NO CODES. And the mechanics don't have a clue what to look at without codes.
Intermittent condition.
This ranger has new fuel pump, new plugs and wires. 176,000 miles on it.
Any ideas?
Thanks!

Try some injector cleaner.....a fuel filter...see if it changes anything.

 

[North Idaho 5.oh]

You could always check for vacuum leaks as well.
the vacuum lines in these trucks are getting old and brittle.
Also grab yourself a can of starting fluid or brake fluid and while the engine is running, spray around the bottom of the intake plenum. If the idle changes at all then you may have intake O-rings that are flat and not sealing the way they should.
I also like the fuel filter idea…. Never a bad idea especially with a new fuel pump.
The pic is what I went thru on my 97 B-series (same as the ranger) but I had a significant timing cover leak on top of a misfire etc…

 

[jhknight56072]

Try some injector cleaner.....a fuel filter...see if it changes anything.

a new fuel filter was supposed to be installed with the new pump, but sometimes it doesn't get done right. thanks, worth a try.

 

[rusty ol ranger]

a new fuel filter was supposed to be installed with the new pump, but sometimes it doesn't get done right. thanks, worth a try.

Its not installed backwards is it?