99 4.0 ohv problems :-(

[jrowe6]

Hey guys, maybe this issue has been delt with before, i expect it has, but i couldnt find the exact answers i needed so I'm hoping actually talking to some people after giving my specific problems will get me where I'm trying to go....

the history...
so, my explorer has just over 200,000 miles on it now. i bought it with 174,000 on it. the check engine light has been on the whole time but i had no problems till recently. i had a buddy at a ford dealer run the codes one time and it was one of the rubber tubes that check the exhaust pressure. fixed that(that was at maybe 180k miles). then the light came back on. replaced the MAF, light is still on(190k miles). after that it ran well for a while. recently i changed my spark plugs/wires and alternator at the same time. after that if i push too hard on the gas the engine stutters like it has a misfire. i checked the wires and plugs and all seem to be connected fine. winter set in and its cold now and the problem seems to be worse. when i start the engine it is harder to start, then while it is warming up it will go through a period or two where its really grumbling. occasionally it will stall out. if i give it some gas and run it above 1,500 rpms for a few seconds then let off it will go back to a normal idle. i can drive it around town fine so long as i dont floor it, but on the highway it can barly run 70mph before im pushing it hard enough to make it stutter. i would take it to someone to have them look at it but im a broke college student and i would rather have that money for parts than for someone to tell me whats wrong. for the record, i put a new iac valve in it a while ago so i know thats not my idle problem. im under the impression its either an ignition timing issue or a fuel system issue. is it possible crappy worn out O2 sensors are causing this? or a weak fuel pump? i replaced the fuel filter not so long ago. so yea, if any of you can put all those clues together and give me a place to start i would really appreciate it. its freezing out right now so i'd rather not spend all day ripping my car apart, break something, then be without my vehicle. ugh....help

 

[35Remmy]

Jrowe, if I were you I would start with the basics. You need more clues! Is the check engine light still on? If it is, you need to run the codes again. I have always had bad 02 sensors trip the CEL. What do the spark plugs look like? Are any of them really dirty or super clean? What does your air filter look like? You should also be testing the fuel pressure. Is the truck running really rich? Do the oil and coolant look ok?

 

[jrowe6]

yes the check engine light is still on. i had autozone run the code over the summer, this was after replacing the MAF...the light coming back on. i dont remember the exact code but it said "running lean". the spark plugs are new, maybe 2,000 miles on them. i inspected the old ones when i took them out and they looked normal. they only had like 10,000 miles on them they looked like i could have just put them back in but i bought new ones so why not put new ones in ya know. i did a compression test on the drivers side cyliders when i changed the plugs, idky i didnt do the passenger side. but anyways, the front and rear cyliders were 155ish, middle was 170ish. i read in my chilton book that those numbers were acceptable. maybe i will check the other side today. and have someone check run my codes....autozone will do that for free so why not. i need to find someone to check my fuel pressure for me. anything else i can look at?

 

[jrowe6]

oh yea....oil and coolant. my oil looks fine. my coolant looks like dog **** bc i put some gasket fix stuff in it a while back bc i thought i had a coolant leak. thats been well over a year ago and i have not put a drop of coolant in it since then. also i changed the oil when i changed the plugs this past time and there was nothing suspicious about it. no water or metal or anything abnormal. i am having an oil pressure issue, but i didnt think it was connected. so here's the details on that.....when the engine is cold and i just start it up the guage shows zero oil pressure. then as it warms up the oil pressure will go from zero to normal. no inbetween. i think either the oil pickup is clogged or the sensor is clogged. didnt have the problem over the summer. it started last winter. i tried flushing the system but that seemed to make it slightly worse. that problem actually started after the first time i used the oil flush. not right after, but soon after when it got cold. that only happens when the engine is very cold and has not run in a while. once its warm the oil pressure is normal right on start up. no weird sounds or anything like that. also, the engine seems to have alot less power than it used to for any given amount of throttle. it feels very weak compaired to what it used to.

im going to go to autozone and get them to run my codes here in a bit when they open. and try to find a mechanic who will check my fuel pressure for me. i'll post the results in a bit.

 

[Joe Dirt]

When you have the codes read, write them down and post them here, don't let them toss parts at you or let them interpret what is wrong...

 

[2000StreetRod]

Oil pressure indicator

The oil pressure indicator on the dash is actually a glorified idiot light. That's why it doesn't fluctuate with engine speed. The gauge is connected to a pressure switch instead of a pressure sending unit. Your oil pressure switch may be intermittent. I suggest you check its electrical connection and if good replace the switch. I've never seen the specifications on the switch but I suspect if your oil pressure is more than 10 psi the switch causes the indicator to read normal. It's a sorry substitute for a real gauge!

 

[alohamonte]

Most radiator gunk kits say you need to flush the system shortly after adding the product... probably shouldnt be in there a whole year. Fluid should be green. You will probably have to replace the tstat too.

As far as the bogging, I replaced the upper intake gaskets and injector o-rings at 140k in my OHV. When I took the injectors out, they looked like they were sitting in mud and was the source of my idle problems.

Youre first step however is to check the CEL. Oh, did you reset the computer after you replaced the MAF? Disconnect the battery for 15 minutes after any engine work because it resets the error code.

Sounds like a vac leak or a problem related to the EVAP system.

 

[jrowe6]

yes i reset the computer after i changed the spark plugs. it was fine for a little while but tripped as soon as i hit the gas hard and the jerking happened. i just had a buddy run the codes with one of those hand held readers you can buy at walmart. idk if those things show everything. what it showed was P0171 & P0174, those are the codes it showed a while ago. at that time it felt like it didnt quite have 100% of its power and had slightly worse gas mileage than it should but it ran just fine and did not have the idle issue or the hesitation under heavy throttle. the question i have is bc those codes are showing up wouldnt that indicate that the O2 sensors are working? isnt that where the information is coming from?

i typed those codes into google and found that alot of people have the intake manifold gasket issue. how can i check to see if that is the problem? on that note, i would expect that to affect my idle because the vaccum would be very great at idle, but as the throttle opens the vaccum should decrease significantly which would lessen the affect of unregistered air getting into the engine so when i get the stuttering at full trottle that doesnt seem like it makes sense to me.

i'm not a mechanic or a specialist or anything buy i have a fair understanding of engines and my instinks are telling me its a fuel shortage issue. i didnt get the change to have my fuel pressure checked today but im going to try to do it tomorrow. i suspect my fuel injectors more than the pump tho. any way i can check them without taking them out? also, is there a way i can check to see if my oil pump is working properly? if its just the gauge i really dont care to fix it right now.

thanks guys

 

[jrowe6]

oh yea, what is the CEL?

and ive checked the little tubes going to the evap canister and everything looks in order. any way to test that?

 

[96eb96]

yes i reset the computer after i changed the spark plugs. it was fine for a little while but tripped as soon as i hit the gas hard and the jerking happened. i just had a buddy run the codes with one of those hand held readers you can buy at walmart. idk if those things show everything. what it showed was P0171 & P0174, those are the codes it showed a while ago. at that time it felt like it didnt quite have 100% of its power and had slightly worse gas mileage than it should but it ran just fine and did not have the idle issue or the hesitation under heavy throttle. the question i have is bc those codes are showing up wouldnt that indicate that the O2 sensors are working? isnt that where the information is coming from?

i typed those codes into google and found that alot of people have the intake manifold gasket issue. how can i check to see if that is the problem? on that note, i would expect that to affect my idle because the vaccum would be very great at idle, but as the throttle opens the vaccum should decrease significantly which would lessen the affect of unregistered air getting into the engine so when i get the stuttering at full trottle that doesnt seem like it makes sense to me.

i'm not a mechanic or a specialist or anything buy i have a fair understanding of engines and my instinks are telling me its a fuel shortage issue. i didnt get the change to have my fuel pressure checked today but im going to try to do it tomorrow. i suspect my fuel injectors more than the pump tho. any way i can check them without taking them out? also, is there a way i can check to see if my oil pump is working properly? if its just the gauge i really dont care to fix it right now.

thanks guys

If those codes are two bad O2 sensors you should play the lottery. They actually are saying the o2 sensors are correctly reporting a lean condition, its doubtful they are bad sensors. I could almost guarantee if you replace them, the problem will come back.

Where did you get the replacement maf from?

Is it new or reman?

Stumbling on acceleration as you described is often a problem with the MAF. Try disconnecting it and see if it gets better. The MAF has a special parameter called BARO (it actually gives you the barometric pressure!) and if its accurate the MAF is ok. You need a good scanner to read that parameter. There are also other tests you can do, but you need a scanner that has live data.

My money is now on the MAF, even though it was replaced. It often sets both of those lean codes too.

 

[jrowe6]

the MAF is brand new. if i unplug it the engine pretty much just cant run. it can hardly idle just sitting there, no way i could drive it like that. i think i got the MAF from napa.

 

[Turdle]

Thoroughly check for vacuum leaks. Also could be an intake manifold gasket issue.

 

[jrowe6]

let me clear up the acceleration thing, idk if i explained it properly. any amount of throttle up to about 75% of full throttle the engine pulls smooth and fine, but at a certain point if i push it down just a little bit more it will start to misfire. it does feel weak up to that point for the given amount of throttle but it does not hesitate or jerk or anything until i push it past that certain point. from a stand still i can push the throttle alot harder before it misfires than at highway speed, which is why i feel like its a fuel shortage. the higher the rpms the less throttle it takes to cause the misfire. when on the highway going up a hill at 65 it can hardly put out enough power to maintain the speed, if i drop down to 3rd gear i can get a little bit more out of it and accelerate a small amount but it will still misfire if i push too hard.

 

[96eb96]

let me clear up the acceleration thing, idk if i explained it properly. any amount of throttle up to about 75% of full throttle the engine pulls smooth and fine, but at a certain point if i push it down just a little bit more it will start to misfire. it does feel weak up to that point for the given amount of throttle but it does not hesitate or jerk or anything until i push it past that certain point. from a stand still i can push the throttle alot harder before it misfires than at highway speed, which is why i feel like its a fuel shortage. the higher the rpms the less throttle it takes to cause the misfire. when on the highway going up a hill at 65 it can hardly put out enough power to maintain the speed, if i drop down to 3rd gear i can get a little bit more out of it and accelerate a small amount but it will still misfire if i push too hard.

Trouble codes have extended data (freeze frame) that the scanner should read. It would be helpful to know if the codes were recorded at idle, low temp, high temp etc. For example, if the codes were triggered under 100 deg coolant temp, it may be a gasket issue. Gaskets often seal as the engine warms up.

Intake leaks are usually related to idle conditions, but as rpms increase more air comes into the system and the intake leak becomes insignificant.

Sometimes a vacuum reading on the engine can give clues, maybe clogged cats? But the lean code is still an issue.

If you have a good scan tool you can read fuel trims at various speeds, and also confirm the MAF is working. A NAPA MAF is likely a reman, even if its not its an aftermarket sensor, and that isn't always the best solution.

I would also like to see a fuel pressure check at higher RPM, to see if the pump delivers enough pressure.

 

[jrowe6]

im going to get a fuel pressure testing kit right now. i'll post the results later tonight.

 

[jrowe6]

got the test kit from autozone.....brought it home and the only adapter missing is the ford adapter.....of course. better luck tomorrow perhaps.

i did bleed the fuel rain where you hook up the adapter, it appeared that there was air in the lines. not sure what its supposed to look like but that seems odd to me.

 

[jrowe6]

fuel rail**

 

[explorerguy89]

pcv valve almost for sure =]

 

[jrowe6]

pcv valve? i wouldnt think that could have such an influence. i'll check it tomorrow.

 

[my98nnj]

Misfire under load would point to either fuel pressure or spark.
Being your getting a lean condition code, I'd start with fuel.
Get a gauge and monitor the FP as you drive. You may have a bad regulator.