Rough idle. Find no vacuum leak. How do I check it to make sure and check fuel pressure?

NERRAD1010

MEMBER
1998 FORD RANGER
2.5L
4 CYL
2WD
AUTOMATIC
164,000 MILES

Truck runs/ idles rough and runs rough between 20 - 40 mph. On freeway 60 - 70 runs much better but not like it should. After driving for 10-20 minutes truck dies whenever I take foot off gas. If I try to start it right back up I have to give it gas and takes 4 or 5 times before it starts. But if I wait just 1 minute it starts up just by turning the key. Not due for a tune up, fuel pressure is fine, no vacuum leak, iac, maf, oxygen sensors replaced, NO check engine light on. Not smoking or burning oil, not overheating, and cat is fine too. Have never had timing belt serviced/changed. What do you think?

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

When it won't start, have you checked to see if there is a loss of ignition spark? I ask because oftentimes, a faulty crankshaft position sensor will fail when it gets hot and then work again after it cools for a bit.

Take a look through this link. It explains the most common symptoms related to a faulty crankshaft position sensor.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

If the truck has a tachometer, see if it moves a bit when you experience a crank no start condition. If it doesn't, the sensor would be a good suspect. Also, if you have access to a live data scan tool, you can check for an RPM signal.

If you determine it is bad, here is a link showing how in genera they are replaced. You can use this as a guide.

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

If you look at the pics below, they provide the directions specific to your vehicle for replacement.

I hope this helps. Let me know if you have other questions.

Take care,

Joe

See pics below.

Images (Click to make bigger)