I have a 02 ranger 4 cyl that is losing power. It has new plugs. Anyone got any ideas. please help. Thanks.

 

How many miles on the truck? Plugs only? Could be wires, air filter, fuel filter, dirty fuel injectors, timing and so on. How does it start and idle? Manual or auto tranny? Losing power in what sense, going up hills, trying to maintain speed, 0-60 git-go?

 

Its got 135,000 miles on it. It justslowly started loosing power a couple of weeks ago. Acceleration, espicially on hills, and wont rev upvery fast.I read some other posts and someone recommended removing the oxygen sensor before the catalytic converter and I did that and it seemed to help some but it is loud and kinda hard to tell if running as good as it should. When I let off the accelerator (with the oxy sensor out) I can hear what seems like backfiring from the exhaust. Its starts like a new one, idles perfect, and it has a manual tranny. This truck has run problem free up til now. 90% freeway miles. Thanks.

 

Could be a plugged/partially plugged conveter.

To diagnose a plugged catalytic converter, you can check intake vacuum or exhaust backpressure. To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust. Remember, though, that intake vacuum can also be affected by retarded ignition timing and valve timing. What's more, some engines are much more sensitive to small changes in intake vacuum than others, so checking backpressure rather than intake vacuum may give you a better indication of what's going on.

Checking backpressure requires connecting a pressure gauge to the exhaust system. Use a gauge that reads up to 8 to 10 psi and is calibrated in 1/2 inch increments. Or, use a metric pressure gauge calibrated in kilo-Pascals (kPa). One psi equals 6.895 kPa. This can be plugged into your O2 sensor opening since you have the O2 out.

Once you've made your connection, start the engine and note the backpressure reading. Depending on the application, the amount of backpressure that's considered "normal" will vary. On some vehicles, backpressure should read near zero at idle, and should not exceed 1.25 psi at 2,500 rpm. Others can handle 0.5 to 1.25 psi at idle, but should have more than 4 psi during a snap acceleration test.
If you find a relatively high backpressure reading (say 8 to 10 or more psi), there's obviously an exhaust restriction that will require further diagnosis. Don't jump to conclusions and assume the converter is plugged because it might be a collapsed pipe or muffler guts.

 

I put the oxygen sensor back in and started to town and the engine started fine and about a mile down the road it started shaking and lost alot of horsepower. Wont turn over 3000 rpms or go over 30 mph or wont hardly pull itself up hills. I will try the tests as soon as I get some gauges. Thanks again.

 

Yep, sounds like plugged converter. As it warms up the guts are expanding and closing off what flow you have tru the converter.

 

USC...I am having a similar problem I believe. I am getting something like a misfire or more like the a gremlin switching off the engine for a split second at just over 4k rpm when cool. As it warms (block temp not water) the misfire/ bucking drops down in RPM to just over/under 3K and becomes more pronounced, IE 500rpm drop on the tach. Plugs, wires, FF, AF changed. Also swapped out coil for new unit with no effect. No check engine light and no codes, and yes PCM will toss codes (checked it by disconnecting a sensor). I am beating my head against the wall..................