I have a 97 ranger and when u initially press the gas down about an inch or so the motor will shake the whole truck and run rough, push it farther and it smooths out and seems fine. It also idles fine. Does anyone have an idea what this could be? I've replaced the fuel filter and the air filter is new. I also cleaned the MAF sensor and the throttle body. The spark plugs appear to be fine and supposedly the wires are newer. I just bought the truck from someone else. It has about 300,000 miles on it. Also, when initially releasing the clutch in first gear, you have to keep the throttle pressed nearly halfway down to avoid sputtering.

 

At 300k, you may just be in need of a rebuild. Before you spend too much time trying to diagnois it, do a leakdown/compression test.


A middle range miss is odd, my thinking is your engine is not putting out sufficent power. Fuel and air are fine at idle and once you get rolling, but your losing compression and power.

 

Probably need a valve job. Does it smoke/use oil? If not, I'd do as ReAX suggested (leakdown/compression test). Have you pulled any codes lately?

 

You're probably right, because running higher octane fuel lessens the problem dramatically. Being that the truck has eight plugs, do i need to removed all eight, or just one side to do the compression test?

 

Hi and welcome to the site!

Just remove the plugs from one side to do the test. You need to other 4 in place to hold the compression in the cylinder being tested.

 

Hey thanks guys, it ended up being a PCV valve. In fact, although the check engine light wasn't on, it pulled codes p1506 and p1721 I think it was, anyway IAC high idle, and rich bank one and two... The PVC valve replacement cleared the codes and got rid of the lagginess. Says a lot about their motors. 300,000+ miles and still running strong. (odometer broke at 261,000 though, so not positive of mileage)

 

NOTE: just because your PCV valve rattles, doesn't necessarily mean it's good. Mine did, and replacement still made a difference.