My 2000 Ford Explorer 4.0L OHV has a serious problem. When i try to start it up(if it does start) it will immediately die unless i give it some gas. When it doesn't die and i let off the gas VERY SLOWLY it will stop at about 350-400 rpms and sputter then jump up to 1500rpms, drop down and die. I replaced the spark plugs, spark plug wires, fuel filter, and i even bought a mass air flow sensor(taking the sensor back tomorrow). none of that changed anything. I've come to think its one of three things; another senosr, a vacuum line, or the timing belt. If i lay on the throttle pretty good and get it up to 1000 rpms or higher it seems to run ok, then i let off and it dies.......any advice? any light you can shed on this subject will help.

 

It may be your iac (idle speed control) Take it off and see if it is dirty inside it can not be cleaned.

 

IAC or speed sensorsounds right. If your rubber vacuum lines are older it is very wise to check them out and replace them if they are cracking when you pinch them - they should be pliable. Also if you have high miles - 150,000 or more it's probably better safe than sorry - replace the timing belt. If it goes on its own some type engines will bust up the valves and pistons when it tries running with off timing.

 

i have to add a few new developments with the problem. The rpms would jump up to 2500rpms then drop and die, not 1500rpm, sorry bout that typo. and now the thing wont even turn on, it tries but never actually starts. i tried using different batteries all of which worked with the same exact results, battery light lit up on the dash board with all three.Also, when it first started running bad, i pulled over and looked under the hood and theres a small black device rightunder the IACwith two vacuum lines plugged into it, well those were blown off of the device( i dont know what that thing is)and i checked the vacuum lines which "SEEM" ok, they still feel normal, not brittle or unusually soft.

 

Vacuum lines essentially suck air in therefore them blowing off means they have pressure instead of vacuum. Something sounds very wrong there. maybe it's a timing belt or chain - with incorrect timing you could get exhaust pressure backing out the intake and popping off vacuum lines.

 

I have been coming to the conclusion that it might be the timing chain, i really hope it isnt because its going to be a real pain to get to it, but i gotta do it myself if i dont want to pay a mechanic hundreds of dollars to replace a 55 dollar part(that is, if its just the chain that needs replaced)thank you for the info, i will come back and post any new developments.

 

Chain or belt they're all a pain - but chains last longer. Don't forget to remove the bolts that connect the timing cover to the oil pan (on the bottom) - provided yours connects directly (usually the timing gasket set comes with the front portion of the pan gasket so don't worry about breaking it). And make triple sure the timing marks are lined up on the gears BEFORE you put it back together. Start by taking off a battery cable. Next - If you have a chain - drain the antifreeze (covers have water jackets for coolant flow a lot of times). Next comes a lot of bolts and nuts - if you don't want to forget where all the bolts go draw a picture(s) you can read and number the bolts quick with pieces of masking tape according to your picture so they don't get improperly placed. If scraping gaskets on aluminum parts don't push too hard on the scraper or razor and accidentally gouge the aluminum bad or you might get leaks. If removing old radiator hoses - try a light twisting motion to free them from where the clamps sealed them on before pulling them off.

 

I really want to do this job myself on my explorer, is there a way to check the timing without removing all the fluids(the vehicle also wont start)

 

There is NO way to check without taking it apart. A timing light only tells you if the timing is set in the gears - not if the gears are shot - so there is no option but removal. You can take it all apart first - and what will happen is your antifreeze will drain into your oil pan if your timing cover is part of the engine block area over top of the oil pan (IF you have a belt and plastic cover this doesn't apply). Then you'll have to drain it all together anyway. If you want to save the antifreeze and filter it back in later (provided it's good) you must drain them separately first. Before you dive in though - your engine has high miles right? And was your oil pressure and temperature good when it did run? If high miles - indicates timing chain. If low oil pressure - oil pump. Some newer vehicles are equipped with a low oil pressure shutdown switch that will not allow it to start without pressure. As long as you had oil pressure and clean battery cables the only other things that would keep it from running are the fuel pressure or timing. Keep in mind - timing is also partially controlled by the computer. So don't buy the gears until you see if they're shot. It could be a computer malfunction also. Many things go awry inside an engine - it's the computers that make a hellish mess of it all and diagnosis not easy.

 

You can check by removing #1 spark plug and put the engine to top dead center, you can check it by the #1 piston will be at it's highest point. Then check the mark on the damper and make sure it is lined up with the pointer. Just be aware it can be 180 degrees out so you may have to turn the engine over one revolution. I turn the engine with a breaker bar and socket. I use a long thin screwdriver to find the position of the piston. Make sure you don't jam the srewdriver in the cylinder or you will have begger problems.
By the way all ford V6 engines have a timing chain not a belt. They are also known for having bad chain tensioners.