2005 Ford Ranger - 3.0L Misfire

[bloughsauto]

I have a 2005 Ranger 103000 miles 3.0 cyl. 4 misfire....it only misfires at idle after engine warms up. Misfire will go away at about 1300 rpm. I have done everything I can think of. Tune up (plugs, wires, coil) swapped fuel injectors, vacuum smoke test, compression test, leak down test, cleaned MAF sensor, Changed O2 Sensors.....I scoped the injectors and plug wires and they graph the same as cyl. 6 ....has anyone had a similar issue???

[Tim Martin]

Without diagnosis here at my shop, I'd lean towards a sticking valve in a guide. We see this occasionally and will produce the situation you are describing. it seems like it disappears as rpms increase but is actually just not being noticed due to engine rpms.

[bloughsauto]

Wouldn't that show up on a compression test?

[liljoe]

Wouldn't that show up on a compression test?

Not always, the valve can be slow closing and at cranking speeds it is fast enough to be good, but at idle speed it is not closed fast enough and that cylinder misses....

[Tim Martin]

About the only way I know of is testing with a good ole vacuum gauge, with the emphasis on good.. At idle it will show a consistent flicker.

[bloughsauto]

Thanks, I am scheduling for next week to check head...,,I will post results.

[Ruger77]

Think of the vacuum gauge as a "running compression tester". More of a dynamic, rather than static, test.

[Tim Martin]

Think of the vacuum gauge as a "running compression tester". More of a dynamic, rather than static, test.

Excellent analogy!

[steven kiser]

not at my shop computer now but if this pertains to topic it may be your issue. i've had issues with the egr port being plugged in the intake for a specific cylinder with these symptoms.

[protraxrptr17]

What did you find? I have had quite a few of these have real bad valve recession. Also had one that had been to every shop in town. Heads reworked, a bunch of stuff. Anyway, it ends up here. Running rich on one bank. After much diagnostic time, I found that one shop had put in the wrong fuel injectors on that bank. Called the owner and he went to the shop and got the injectors they removed. They were also wrong. Ordered 3 new ones from ford and fixed the truck. Find out as much as you can about the history of what has been done.