Hello,
I have a 2000 Ranger XLT that idles rough (smooth on acceleration and highway speed) and the check engine light is on intermittently. I have changed the plugs, coils, wires, cap and all 3 oxygen sensors. Again, runs smooth as silk at highway speed or any speed besides idle. Which way should I go from here? Thanks in advance

 

Welcome to the forum

Get codes from computer, WRITE THEM DOWN
Auto parts stores do this for free

Codes need to be exact, there will be several codes for each system in any vehicle, "I got an O2 sensor code" is of NO VALUE, there are 20 O2 sensor codes, need exact code, because with 20 to chose from computer will have a reason it picked that ONE specific code.
Same applies to ALL OBD codes

Misfires at idle could be compression related, dirty fuel injector tips(run seafoam in gas tank), low system voltage, failing alternator, so get the codes and see where that gets you

 

Thanks, I'll do that. Last time I did it it said misfire on cyl. #5. I cleaned the MAFS today. The light went out and I and drove for about 25 miles. Came back and cranked it a few hours later and the light is back on... Could the MAFS be bad?

 

Check the codes, computer can detect failed or failing circuits, it can't detect failing sensors, just if voltage going to or coming from the sensor is out of range.

While its popular to swap sensors, 90% of these were working fine, sensors rarely fail, usually its just a dirty connection causing the voltage issue, so unhook connections and have a look, sometimes just unplugging and plugging back in a connection cleans it enough for wiring to work again, which is why people report "new" sensor fixed the problem, lol.
It wasn't the "new" sensor, it was unplugging and plugging back in the connector that fixed it.

 

Thank you...I sprayed the connection with cleaner yesterday when I cleaned the sensor. I'm gonna get the parts store to check the code again. I'll report what they say. Thanks for your help!!
Dan

 

Good investment is an OBD2 Bluetooth reader, $20-$30
These work with a Smart phone and FREE APP
You can read the codes and see LIVE DATA via Bluetooth link

And these work on ANY vehicle sold in the US or Canada since 1996, its the LAW, not an option for car makers, not a Ford thing, doesn't matter where the vehicle was made, by law if it was sold in the US or Canada it must be OBD2 compliant
So an investment if you plan on owning cars or trucks, will work in to the future

The Live Data is great, you can see what the computer sees for each sensor, very helpful in troubleshooting

 

So the code showed a misfire on cylinder 5 (P1000 I believe). Pulled the plug, has oil on the threads. Gonna do a compression check this morning...what could be the causes of an oily plug?

 

Leaky valve cover if oil was on the threads of spark plug, if oil is on the tip then leaking valve guide seal

P0305 is misfire on #5

"I believe code was..........." is worse than no code, you end up looking in the wrong direction, like saying "I have a flat tire, so what wrong with the engine?"

You can look up codes here: OBD-II Trouble Codes : The Ranger Station

P1000 - OBD-II Monitor Testing Incomplete <<< which means computer was reset and the computer hasn't finished new testing of EVAP, and other systems, which requires a few "drive cycles"
One Drive cycle is full warm up of engine(engine temp 190degF) and then full cool down(engine temp under 120degF)

 

thanks Ron, I did a compression test and posted the results. Looks like I'm going to need some major work

 

You compression test post is not working, just post numbers here, type them in

 

Not working on Chrome or Firefox either, but it's sure making the processor work trying to load a blank page.

 

sorry about that Gents.. Here are the numbers ;

1. 75
2. 110
3.90
4. 100
5. 30
6. 60

 

I wonder where Ron went to, if those reading are correct, then that's your misfire problem, should be at 165 for a new engine and no less the 150.

I would do them again and if you haven't done this already remove all the plugs and do the compression test again with no plugs in the engine.
Hold the accelerator pedal all the way to the floor to allow maximum air flow into the engine.
Crank it as many times as necessary until the compression gauge needle reaches its maximum reading.
Make sure the compression tester is seated properly, some are too thick to fit down into the spark plug hole.

Add a couple of table spoons of oil to a given cylinder and test one at a time, start with number 5 as that is the lowest.
If the compression improves, then you have a ring problem, if it doesn't, then you have a valve/seat problem.

The 3 litre also suffered from soft valve seats, but I think that was after 2004, but maybe someone put on some used heads from a junk yard from those years ???

The timing chain should be considered, but only as a last option as a problem.
It's just a simple chain with no tensioner and I can't see it so worn that it jumped a tooth, threw the valve timing out of whack and caused low compression.
It's an interference engine, so if it did jump a tooth or two, the pistons would most likely come up and bend the valves.

It could just need a valve job, but those numbers a pretty low even if the valves and seats were in bad shape, numbers like that don't happen until you get more then 300k on an engine.

What's the history of the truck, how was it driven ?
How many miles ?

 

Thanks for your response..I'll redo the test and let you know. The truck only has 152k on it, I've had it since 02. It's been taken care of, the toughest part of its life was probably when my daughters (2) drove it while they were in college. Even then, it was local and I was there to see about any issues that came up. I should mention that those numbers were on a cold engine, all the plugs out but I didn't floor the accelerator. The fitting screws into the plug hole so I think that's ok. The truck runs well, just a rough idle, smooth at highway speeds. Thanks again!

 

Not good readings, as in not done well

Engine wouldn't run at all if they were correct

All spark plugs need to be removed for mechanical compression test
Cold engine is fine
Use screw in type compression gauge, just needs to be snug, you don't need to use a wrench to tighten it
Press gas pedal down to the floor and hold it down, this turns off fuel injectors and allows Max. air flow into the cylinders
Crank engine over until you hear at least 5 "hits" of compression stroke on the cylinder being tested, you will hear "it" trust me, lol
Write down cylinder number and gauge reading
Release gauge pressure, compression gauges hold highest pressure, as they should, so they all will have a valve that releases pressure so they can be used in next cylinder.
Install gauge in next cylinder

3.0l Vulcan engine used 9:3:1 compression ratio, so even with 150k miles you should expect 165-170psi

3.0l also doesn't use timing chain tensioner so unlikely for chain to skip, and crank and cam gears are both Keyed so valve timing is usually not an issue when compression is low

 

Thanks Ron, the only thing that I didn't do that you described is hold the accelerator open as I was turning the ignition. I hope that that's going to make a difference. In number 5, a buddy told me to put a little bit of oil in the cylinder and then do it again. I did that, compression went from 30 to 190 on that cylinder. So, armed with this new knowledge I'll be redoing the check as soon as possible. I'll post the results. I really appreciate your help

 

It only idles rough, but drives great. Prolonged idle causes the check engine light to blink and the vehicle runs VERY ROUGH (barely drives). Turn engine off, restart, it runs fine. This makes me think its not mechanical, but electrical/fuel instead.

I have already replaced plugs, wires, fuel and air filters. Inspected coil pack, multi tester shows ok. Swap #2 and #6 wires, engine runs the same, fault still misfire #6 and 1st 1000 rpm.

I'm thinking it's the fuel injector, but since it's the hardest one to get to (thanks Murphy) wanted to get a 2nd opinion.