2001 Explorer mis firing when hot

[markedman450]

So...the store continues...My explorer after driving an hour like on a highway will start to have problems when i try to accelerate. Its like the hotter it gets the worse it gets. The dealer said my rear cats were clogged so i put new ones in. Problem seem to go away but now its back. Heres what happens. Start the car it runs great, start driving runs great. If im on the highway for like an hour i start noticing a miss in the engine. Then if i try to accelerate once it gets past 4k rpms it starts to miss-fire, feels like the engine is cutting out for split seconds. The longer i try to drive, the worse it gets. Another hour of driving and i can barely accelerate above 2k rpms before it starts to cut out, and once it cut off soo bad it stalled. It started right back up and ran fine again for a few minutes before the problem happend again. New parts on the explorer include rear cats, fuel pump, coil pack, etc. Also cleaned the idle air control and the MAF already. Fuel filter is only 6 months old, wires are auto light and about a year old. Ive been bouncing around ideas like the o2 sensors, TPS sensor, front cats or muffler but im completely lossed to what could be causing this. No check engine light and no codes, just feels like the engine is cutting out fuel and its almost shutting off.

ANY help is appreciated and id love to figure this problem out. Any Ideas!?

 

[CDW6212R]

Tough problem. First what fuel pressure does it actually have, please know that. If you have 62psi at idle and under throttle then the fuel is likely not an issue.

Have any modifications been made, odd things etc? How do the spark plugs look, and I would still be suspicious of the plug wires, not being just changed. What is the water temperature as it runs, does it change at all?

 

[markedman450]

I have a warm air intake i put on last year with a heat shield. Plugs are brand new, i figured the same so i had an auto shop put some in, now they are champion so i know they are not as good so i have motorcraft plugs and wires on the way. I was thinkin the same on the wires, just never had wires become so bad so quick and cause this much problem. I dont know the fuel pressure ill have to check, but it might be hard to check since i have to drive over an hour before even seeing the problem. Water temp stays the same, no overheating. I know cylinder 6 was having issues with the plug goin out every 6 months, found a clogged pcv valve and oil was all in the cylinder, got that fixed 3 months ago.

 

[CDW6212R]

My 99 SOHC ran good to start with in February, but for over six months it seemed like it had a slight vacuum leak. My issue turned out to be fuel pressure, I had 55psi at idle, dropping to 50 with winging it. I installed a used assembly and have 62 psi with almost no change with any throttle.

There are so many things which can cause similar symptoms, that it usually comes down to checking the same basic stuff.

 

[markedman450]

So fuel pressure is a def. check...any other ideas incase the fuel pressure checks out ok

 

[CDW6212R]

What kind of code scanner was used? If there is no code at all then a vacuum leak is unlikely, that would cause so much trouble. Some scanners do not get all of the codes, and some pull nonsensical codes.

My Scangauge does very well to pull the important codes, but I was getting two codes that meant nothing, a P1000 and some other 5000 number. I have heard of people having Autozone check their codes, found none, yet a dealership got codes the same day.

Without some PCM code it would have to be something outside of that range of parts, like the plug wires. Those wires are hell to pull off of the plugs, they can easily be damaged. Do you know how they were removed the last time? You can trust that they were good when new, but each time that they are removed, the mechanic knows how gently they were treated.

I have damaged a couple in my many plug and wire changes. I'm not saying that that is the answer, it's just that the list of choices are few, with no codes. Regards,

 

[markedman450]

Ill def. check the fuel pressure. Whats the easiest thing to buy to check that. Also im def putting the plugs and wires on when i get back. Hopefully its that.

 

[markedman450]

updates

So...i get back from vacation, left the car sit for days with the battery off. Start it up and take off from New Jersey. I live in central pa so its about a 3 hour drive. Within 45 minutes the miss is there and getting worse as i drive. Its like the car just keeps shutting off when you give it gas and the more you give the worse it gets. So i pull over and get gas, figured give it a few minutes to cool down. Explorer still had roughly half a tank of gas left. Start it up, take off and for the next 2 hours could not get the symptoms to come back. I ran it hard the whole way home, punching the gas, turning overdrive off, etc to see if i could get it to come back. Never came back at all, was like it was back to full power. So now im thinking wtf. I have noticed the symptoms happen when im under 3/4 tank of fuel, and never occur when i fill it up. Could i have some bad dirt in the tank maybe?? Fuel filter is less then a yr old but im gonna change that tomorrow on top of new motorcraft plugs and wires. Ill also check the fuel pressure. Any other ideas???

 

[CDW6212R]

I'm suspicious of the fuel pressure. My leak was in the lower rubber line between the pump and regulator. Basically I was losing a small amount of pressure, enough for CEL codes but not enough to make it run badly. That is curious,

 

[cjones101812]

if push comes to shove, check the rubber hose at the fuel pump in the tank. check fuel pump, check for dirt in the tank, and the sock on the pump.

also, check the baffles in the tank to make sure one isn't broken.

 

[Turdle]

http://www.scantool.net/products/product_info.php?cPath=8_1&products_id=41

get one of those-so you can see what is happening.

I suspect the maf sensor-IAT sensor assy.

 

[markedman450]

Well i pulled the fuel filter today. Alot of dirt came out of the back end of it when i emptied it. And even after letting it sit for a few hours, i could not blow at all through the filter. Put a new one on and so far so good, but i wont be able to check until i get to drive it for a decent run.

 

[markedman450]

Well since the fuel filter change the car hasnt bucked under acceleration at all. But once again today, being under half a tank of gas it gave me another issue. Whenever making a sharp turn where it was almost idling, even if i was giving it alittle gas, it would stall right out, i coast to the side of the road, and it fires back up. It did this for 3 turns in a row, then when i stopped at a red light, it tried to idle and just shut off again for the 4th time, but once again started right back up. I stopped and filled the gas tank up quick and it didnt do it again, i did notice it was still having some issues idling but it didnt stall. Now last year i have the fuel pump replaced because it wasnt holding pressure...Could this be a similar problem again? What and where can i buy a gauge to messure the fuel pressure?

 

[cjones101812]

you may be able to borrow one from autozone (the ones out here loan out tools).

you'll probably need to do what i said in post # 10 and if dirty clean the tank, blow out the fuel lines, clean the injectors, and replace the fuel filter again (because the first one got clogged so fast).

if the pump is bad, remember to replace the sock(strainer)

 

[markedman450]

Yea the fuel filter was really clogged when i replaced it. Would those symptons cause it to seem to act up when its under half a tank. Its almost like when its full the pump doesnt have to work as hard and when its lower on gas, thats when the problem starts. Longs drives it starts bucking like its having a fuel cutoff issue, and every now and then when im making slow turns it just stalls out.

 

[CDW6212R]

If anything was noticed in the fuel filter, I'd suggest a fuel pressure test, and inspection of the whole tank. Pull the tank and pump/regulator. Confirm fuel pressure first though, you might be wise to have parts ready when you get the tank out.

 

[markedman450]

Well they ran a fuel pressure test, haha its not low. Its really high! Its running around 90-92! SO the guy thinks they either put the wrong pump in, or the regulator is bad already. I just had it replaced one year ago haha. He thinks the regulator is up by the engine bay, i thought it was attached to the fuel pump. Would the high pressure cause the bucking, stalling, especially stalling when on half a tank of gas??

 

[CDW6212R]

The regulator is at the pump in the tank for all 99+ Fords. The regulator would cost close to $90 by itself as I recall. I took a chance on a used assembly for $38 total for mine. It's a hard call to make, I have a friend with a Toyota and the same dilemma. The pump is near $100, like the regulator, so which do you buy, and new or used.

 

[markedman450]

I just want it running good again...im close to just trading it in and getting something else. I heard theres three parts it could be. A fuel pressure regulator, the pump itself, or the fuel sending unit. I know they replaced the pump last year, and so far everything thinks its the sending unit or the pressure regulator. Its becoming un-driveable! One time it runs fine, then no even 5 minutes down the road, constant bucking like it wants to just shut off.

 

[CDW6212R]

Yes I do understand. My 99 is my work vehicle, I had to decide whether it was likely that more than one part would be bad, and whether it would be clear when out of the tank. I was expecting to find a tiny hole in the rubber hoses at the pump, and needed to be able to do the pump and/or regulator if needed. I did find a tiny slit in the side of one of the small hoses, that was my low pressure cause.
I took a chance that the used assembly I bought would be good. I tightened the hose clamps gently, and installed the used assembly.

With a 90psi reading(are you sure of that), I would be betting on the regulator and not the pump. I would buy either a new regulator, or a whole used assembly like mine. The price I found on eBay made my choice easy, check there first. Good luck,