2000 4.0 ohv/auto 4x4, 69k miles. After the truck warms up & been driven about 10-15 minutes, it starts bucking & kicking, rough idle when sitting there, regardless if in park or in gear. Much worse with the a/c on. Also does it jcruising down the road. Runs like a raped ape when floored and doesn't hesitate or anything. Problem is only at idle or constant speed. Gas mileage is poor in my opinion, around 14/16 (city/highway). Actually, there are times like last night it did considerably worse on the highway (around 12) and was bucking and rounning rough to the point I was ready to pull into a dealer and trade it off. Its done this ever since I've had it but is getting worse. Its been int he shop twice in the last 4 months for this and other problems. In April, they ran a full set of diags & everything was as it should be, no codes or nothing. Even at idle, it was twitching like road not yet dead and the mechanic said it was fine... BS. I've had 2 other 4.0 ohv rangers and they didn't run like this.

This time around, it was also pulling the crap of dying when you put it in gear, idle spiking up periodically (mostly when you start it up) and sometimes idling low and trying to stall. It died last Friday pulilng into the garage. after telling the tales of it antics, they started it up and pulled it around back and it ran perfectly for them the couple days they had it. After a half hour ride with the main mechanic, it finally started its bucking & kicking crap. He wasn't too concerned with it, stating they will do that. I don't buy it. it did suggest maybe a full tune up and havivng the fuel injection system flushed or it coculd be an injector that has a small leak in it. As far as the dying in gear, he suspects the idle air control valve. I've changed plugs & wires, new air filter & ran seafoam through it a couple of times. The gas mileage seems to go up for awhile after the seafoam, but gradually declines and we start the running rough crap again. Haven't changed the fuel filter yet... on the list.

I really need some help on this! I'm at a point I'm ready to get rid of this truck and it won't be replaced with another Ranger. Unfortunately I don't have a scanner (which probably wouldn't do any good, as it wasn't posting anything before) and am not a mechanic. Other than an K&N drop in air filter, its all stock and will probably stay that way. This is getting rediculous.

 

ditch the K&N
get a new IAC
unhook the battery for atleast 15 min
get a new fuel filter.

see how she runs after that.

 

stupid but common question: how hard is it to change a fuel filter on an '00? I've heard anywhere from easy to nightmare. I know its on the frame under the driver's side, but don't remember much else. If an inertia switch needs to be turned off, where would that be on the truck? I've done a quick search on the site and heard of different styles requiring different tools, clips and perhaps a midget...

yeah I know, look at it and go from there... slated for Sunday.

 

what i did with mine which yours should be similar is there are 3 clips, you can use a flat head screw driver and needle nose pliers or go buy the actual tool from autozone.

once the clips are loose slide the line off the filter. this is when the messy part starts. prolly going to get fuel all over, i did mine in the gravel driveway so that it just evaporated.

i did not turn off the inertia switch and let it run out of fuel.

the IAC should be pretty easy its on the side of the truck.

if none of that fixes it i say change the fuel pump.

 

You may want to do a search for these topics. A lot of threads show pictures and what not. Believe me, you will get your answers more quickly. I was able to get a pic by pic info on how to do a lot of repairs and mods.

 

Agreed. as I edited my last post, I need to climb under it and see exactly what's there. I'm in between meetings at work & starting initial research on it. I turned up about 50 threads with similar problems and need time to go through them and see what's relevent and not.

 

Just don't give up on the Ranger! I had a real bad electrical short, and with this site and the help of these guys, it's running strong. Good luck finding out the problem.

 

Any updates?

 

Update? ok, here's an update... I've cleaned the MAF, ran about every conceivable cleaner through it and the damn thing still runs like crap. I've replaced filters, plugs, wires with no improvements.

I'm asking can someone reasonably local who knows these things please look at this gawd damn thing and tell me what's wrong with it. I've had a mechanic look at it twice and he gave me a line of crap that this is how it should run. I know better.

Though I don't want to, we are seriously considering trading it off or selling it and it WON'T be replaced with another Ranger.

 

Yeah. tried disconnecting a few times, once all weekend.

It runs fine til after it warms up and you've been driving it awhile (15-20 mintues.) That's when then fun begins. Much more noticible when the A/C is on.

 

SAMS DAD......do your rpms drop down below the 500 range? cuz mine used to idol around 725 or so then when the ac is on or at the bank or wahtever in out out of gear the rpms would just out of nowhere dip down into the 450 range? ....mine turned out to be the TPS. sounds very very similar to my problems i had. crappy thing way my TPS sensor didnt even throw a code so i spent close to 300$ in parts i didnt need. thats my $0.02

 

does the truck make any particular noise when it hesitates or sounds rough? Maybe check the exhaust or cats. my truck had a lot of the same symptoms when the cat fell apart. Worth a try if it you havent had any luck yet.

 

check for vacuum leaks by spraying throttle body cleaner over the vacuum lines, hoses, upper intake manifold, PCV hose. If the engine revs up with the spray thats where the leak is. This is how I found that my EGR hoses had a leak, so I replaced them and now the truck is running fine. When I looked at the hoses they looked brand new, but with the spray, it obviously had a leak. Don't trust your eyes when you check for leaks on the hoses.

 

update:
I checked the PCV & it is shot. I replaced it and though I've only driven it a few miles. Well, its too early to tell, but it is promising. I did notice a bit of bucking while idling in the parking lot. As far as gas mileage, one tank got about 20mpg (90% highway) averaging 70-75mph 87 octane, the next was about 13-14mpg (85% highway, but driving a bit faster, 75 mostly occasionally hitting 80, to avoid being ran over by semis, about 2x the distance as the previous trip), 87 octane. The last one is 15mpg, about 75% in town, 89 octane. All of those were prior to replacing the pcv. I did fill it up last night and have only driven 5 miles prior to changing it, so I should get an accurate account. Still need to change the fuel filter & it does need an oil change.

To answer a few other questions, the rpm's don't really change, though the needle will move a tab but, but it usually idles about 900-1000. 1500 or so when its cold. There are no odd noises, whines, clicks pops or the sort. You punch the gas and it takes off with no hesitations.

 

had a new garage look at it and they got their hands dirty with it. They found the fuel pressure regulator was stuck closed, running about 15psi over normal. The theory is the computer is trying to compensate for less fuel by burning richer, potentially fouling plugs and such which would cause the rough idle & poor mileage. After replacing the regulator and fuel filter, it did run noticibly better for awhile (maybe a week.) But it came back with a vengence. Now if the truck has been sitting over night or for a few hours, it takes longer to start (10 seconds or so vs. 2-3 seconds.) Shut it off then start it again a few minutes later and it takes a normal 2-3 seconds. The guys at the shop are scratching their heads. The only thing they can possibly think of is maybe the fuel pump relay is sticking or not engaging initially.

 

The fuel pressure regulator on your '00 Ranger is in the fuel tank with the pump, so if the shop didn't drop the tank or take off the bed, then they didn't replace the regulator. I have a feeling they simply replaced the fuel injector pulse damper (which has nothing to do with maintaining fuel pressure but looks a lot like a conventional FPR) located on top of the engine, passenger side. I also have the feeling that the shop may have wrongly diagnosed the fuel pressure as being too high. The fuel pressure limits for your '00 are 56-72 psi.