99 explorer sport please Help!! Can't figure this thing out

[Travis Wilcox]

Forums>Gonna need lots of help>


Hey guys, I'm new to this so please bare with me. My wife and I recently purchased a 99 explorer sport for our daughters first vehicle. Shortly after we bought it man did the ol' problems arrive. Started off with the transmission feeling alittle jumpy and unsmooth and a loss of power. I had it scanned and received all types of fun info. Misfire on cylinder 4,5,6 o2 sensors (one burning rich, one burning lean) transmission gear 4 wrong ratio, and a rear speed sensor.. so here's what I've done.. I replaced the trans valve body gaskets and all new trans fluid and filter, I've replaced fuel filter, spark plugs, checked for vacuum leaks (which so far I haven't found).
After all that not much has changed, the vehicle feels like it has no power in gear 1 and doesn't kick in to OD (passing gear) but here's what's stumping me.. if I put my foot to the floor all of a sudden the thing will wake up, sound like I ripped the muffler off( normal driving you don't hear any exhaust leaks, even reving it up) and it will have plenty of power gear 1 and OD passing gear will start to work like it should. But is has to start sounding like a tank for it to have the power it should normally, I'll pull it in the driveway when this happens and rev it up and the exhaust pops and gargle like the manifold just decintigrated and then.. minute goes buy and it all goes back to being quiet, no exhaust noise even when reved up and sounds like a normal engine. So yeah..I need all the help I can get, thanks everyone for reading my book lol

 

[fast_dave]

Travis - Welcome to the forum!

Lets start with the basic question - what engine is in the Sport?

Is it a 4.0 OHV or 4.0 SOHC engine?

 

[Travis Wilcox]

4.0 sohc

 

[XLTrunner]

Partially plugged cat convertor or muffler?

 

[Travis Wilcox]

That's actually kinda what I'm thinking XL, it's the only reason why I can think the exhaust gets loud when the power shows up. Any suggestions on how 5o check for that or am I just gonna have to bite the bullet and pull the cats off to inspect them?

 

[koda2000]

Is the check engine light (CEL) on? Does the bulb light during the bulb check (key in ON position)? Have you scanned for TDC's?

When faced with multiple unknown problems, I like to begin by doing a compression test and/or a leak-down test because that is the best way to assess an engine's health.

The Ford 4.0L SOHC engine is know to be the least reliable of the possible Explorer choices and can begin having timing chain related problems with as little as 75,000 miles. Unfortunately, timing chain repairs are very expensive (due to the labor cost of having to remove the engine to change components) quickly exceeding the vehicle's value. The V6 5-speed auto transmissions are also on the weak side. I've owned 3 SOHC Explorers and I'll never own another one. One blew up, one has the "timing chain death rattle" and one had a rebuilt engine and survived 50,000 miles before I unloaded it. I'm not trying to scare you, but IMO the Ford 4.0L SOHC engine is a poor choice.

There are many things that come to mind regarding the the symptoms you describe, most of which will set the CEL. Using a good scan tool, reporting ALL TDC's and other data will help us determine where you should be looking, but start with a compression test (warm engine, throttle body held open during testing). Some things that come to my mind that might be causing your issues (listed in no particular order) below, but you have to do your diagnostics, please don't just start throwing parts at your engine.

Clogged cats
Bad/dirty MAF sensor (clean with MAF cleaner)
Bad throttle position sensor
Leaking upper/lower intake manifold gaskets/O-rings (common problem on Job 1 SOHC engine)
Bad cam position sensor (controls fuel delivery timing)
Bad pre-cat O2 sensor(s)
Bad/damaged DPFE sensor (they tend to melt from the heat)
Bad/dirty EGR valve and/or leaking EGR pipe
Damaged intake manifold
Valve or piston damage
Low fuel pressure (clogged fuel filter or worn out fuel pump)

If when running your engine rattles like a diesel engine, that would be the dreaded SOHC "timing chain death rattle", in which case you may want to cut your losses. This can also cause the engine to have jumped time, which will really make it run like crap, but eventually the engine will jump-time to the point where the valves will slam into the pistons and destroy the engine. Sometime a timing chain will break and blow a hole in the valve cover.

 

[Travis Wilcox]

Thanks for your response Koda, the original codes I got from scanning I've listed in my first post but yes it did show o2 sensor faults one lean one rich, and the misfire in cylinders 4,5,6, when I had the scan took connected and checked the spark on those cylinders the misfire was only intermintant. Didnt show any other engine faults just that gear 4 ratio was off and the rear speed sensor. The engine runs smooth, good idle no rattles or noises. The guy we bought it off told me it sat for a little while which also leads me to believe that I have a cat that's partially clogged. I'm going to replace the speed sensor this weekend. I have checked the egr pipe and haven't found any leaks. I cleared all the codes and after I replace the speed sensor this weekend I plan on doing a complete scan again and will let you know. Depending on how much time I have I might try and check out those cats this weekend as well. Hopefully eliminating the cats as a possibility will point us in a better direction.

 

[CDW6212R]

That does sound like the cats may be a problem. Checking the cats is common for a muffler shop, or dealers etc. They drill a hole in front of the cat, and measure the pressure inside there. Clogged cats increase back pressure a lot, besides the pressure check only cutting it all out can tell.

The front O2 sensors are good to replace with age, if they are easy to loosen, that's a good step.

The rear speed sensor is the ABS sensor, it's used for the transmission shifting as well as the ABS, PCM and speedometer. That might solve the trans code you have.

For the SOHC, be very aware when starting it each time. Use only the best oil/filter, and air filter, that you can find. Poor maintenance of those items hastens the valvetrain noises and damage. Some people have begun a habit of pushing the gas peddle to the floor, and holding it there while they turn the key to start. That keeps the engine from getting gas until the peddle is let go, and also builds oil pressure before starting. They let off the gas after a couple of seconds of the starter cranking, and the engine immediately starts right up, with better oil pressure to begin with.

 

[Travis Wilcox]

Thanks guys for your advice. What two sensors are up in the thermostat housing, I know one is the coolant sensor, was curious what the second one is, also as I'm trying to replace the coolant sensor( it's been reading low, just barely over the C mark but I'm getting plenty of heat) I see that somebody must have cross threaded it and only have it threaded half way into the housing. Now as I'm trying to remove it the brass threads in the housing are turning with the sensor and it doesn't want to come out. So I'm wondering if I do get the thing out. Any suggestions on fixing the stripped thread insert without buying a whole new housing?

 

[koda2000]

One is for the PCM and one is for the temp gauge. Don't try removing them, they'll most likely start leaking and then you'll end up replacing the complete t-stat housing (which is expensive).

 

[CDW6212R]

One is for the PCM and one is for the temp gauge. Don't try removing them, they'll most likely start leaking and then you'll end up replacing the complete t-stat housing (which is expensive).

Ditto, those sensors are basically never touch items. The T-stat housing is a known problem that they never recalled, but there was an improved version put on the later models. That was hashed out on the forum here about ten years ago. People would disturb them to get access to the front external tensioner in the left head, and then couldn't reseal the sensor.

Most likely you will have to replace the whole housing, plus the sensors. I think what was most feasible, was to buy the updated later housing, say 2002 model, just the top half, which came with two new different sensors, and make that work on the stock lower housing. I don't recall the details of how that was done, but it was described in good detail, and should still be here somewhere. Work on searching for the threads about the thermostat housing, leaking or cracking, and see what it costs now for the 4.0 SOHC upper T-stat housing.

 

[Macgiobuin]

Re: transmission gear 4 wrong ratio. This happens when your PCM directs the high gear/overdrive band to activate, which it is not doing. The servo fills with pressurized fluid, which presses on the band tang and stops the drum from spinning, causing the planetary gears to engage. Your 3rd gear is 1 to 1 and your overdrive gear is .75 to 1, but only one of these is engaging. If you step on the gas to floor it, the PCM will change the gear all the way down to 2nd gear. Bottom line is that your band is broken, and you need to take out the tranny and either replace the band and/or rebuild the whole tranny when it is out. Probably the tang has broken off. I've had examples of a new transmission that needed only a new band and no other rebuild necessary, but you can make that assessment once you crack open the case and look at the conditions.

 

[swshawaii]

Here's the lower t-stat housing upgrade Don's referring to in post #11. (Motorcraft RH-144)
4.0 SOHC plastic thermostat housing

Austekk aftermarket aluminum kit. Check eBay pricing.
Austekk - ATK-8592-AGCS - Thermostat Housing w/Srew In Sensors . Austekk Auto Parts

 

[Travis Wilcox]

Ok guys, I'm hoping to have a lot more answers for you this weekend that might help diagnose this thing. The weather In PA this week has been horrible so I haven't accomplished everything I've wanted to, but I got a little bit done. For starters I did successfully replace the coolant sensor with a new one with no leaks, but for some reason now it's not working at all, the gauge doesn't even come up at all but I'm still getting heat, I read somewhere we they suggested not to put any teflon tape on it (which I did before reading) because it wont get a good ground, but with the housing made of plastic I don't see how that would be a problem, am I wrong? Also I read something about a breather hole in the thermastat that needs to be aligned,which I replaced with new while I was at it, I didn't take any notice of that so is that a problem? So anyways, one of my projects is to try and figure out why I'm not registering any temp. On to my next.. I did replace the rear speed sensor, and I cleaned the MAF sensor (with the right cleaner) I cleaned the throttle plate, checked the cats, they're not clogged. I wasnt able to run any codes or erase any codes this weekend because my neighbor who owns the scanner wasn't home. I tried to clear the codes by removing the positive and negative cables off the battery and holding the two cables together for about 5-10 minutes, not sure if that worked, I'll find out this weekend when I get it scanned. I took it for a ride, still has no power during take off, almost feels like the brakes are applied, and after its warmed up and pulled back in the driveway, the idle acts very rough and unsteady. It clears up after a minute. The lower gear didn't feel this doggy until after I replaced the trans fluid(synthetic) and put in the valve body gasket( I took a lot of time and care to make sure I did that correctly) is there any chance it doesn't like the synthetic? The shaft solenoid thats in the transmission I did have that out and inspected it cuz I've read that they are a common problem, the tip has a small dimple in it but really wasn't as bad as many pictures I'd seen of bad ones. Wondering if sense I disturbed that if that's any of my problem? But would that affect my gear 1? Sorry so long winded, just planning on attacking several things this weekend and will take any advice.

 

[koda2000]

Your taking information regarding rattle valves and grounds from 2 different engines. Your SOHC V6 doesn't not require a ground for the temp gauge sender because (as you noted) the housing is plastic. Secondly, your t-stat mounts horizontally, so the position of the rattle valve (assuming the SOHC's t-stat has one) doesn't matter.

Are you sure you changed the sender for the TEMP gauge and not the coolant sensor for the PCM? They're located right next to one another.

You should never clear codes (with a scanner or by disconnecting the battery) until the problem(s) are solved. By disconnecting the battery w/out knowing what codes may have been there, clearing codes does nothing to correct a problem or make your care run better and it can take quite a bit of driving to get the codes to come back again, or they may come back immediately if you're lucky. Even if the CEL isn't lit there may be pending codes which would be helpful to know. With all the sensors on today's computerized vehicles it was determined that, beginning in 1996, manufactures needed to follow common standards to help mechanics (and DIY'ers) figure out where to start looking for problems. Without the trouble diagnostic codes (TDC's) it impossible to know where to begin. Also, TDC's can't be taken at there face value. Wires can break and sometimes one problem may generate multiple codes. For example, you may receive a code that indicates a misfire on cylinder 3. That's just a starting point for further diagnostics needed. Is it the spark plug, the plug wire, the coil, the fuel injector a bad valve, a cracked head, a blown head gasket, or a piston that's causing the misfire? A vacuum leak can generate multiple codes when the problem is a simple broken/cracked vacuum line. Sorry to go on, but owners clearing codes w/out knowing what they are is a pet peeve of mine.

 

[Travis Wilcox]

Yep I'm positive it's the right one. The old one was only reading just above the "C" mark, now the new one wont even go to that. I double checked the plug, mine is a red plug and the wire is red/black, it is a two wire plug same as the other sensor which has green /red wires. I guess I'll have to test the wires for a break and do an ohm test on the sensor. Anyone know what ohms it should put out?

 

[Travis Wilcox]

Welp, I gave the ol' girl a few laps around the block and am starting to see some improvements (knock on wood) checked the trans fluid and it was low, I didn't know I had a leak around the pan, it's been raining and snowing all week and I have a dirt driveway so hadn't seen the wetness. I topped it off with some Lucas trans fix and my power is returning from first gear. I didn't get a chance to check tonight but what's the odds off me putting the coolant sensor plug on backwards? I'm not sure it would even fit that way, but the coolant temp shows way below C like its bottomed out. I just wondered if I reversed the polarity lol.

 

[koda2000]

I don't believe the connector plug would go on backwards. Bad sender, wrong TEMP sender, bad connection or wire. It's even possible you got a defective t-stat. Have you rechecked the coolant level in the radiator? SOHC's are notoriously difficult to get the air out of the cooling system once refilled. It's referred to as "burping". If there's air in the system it tends to get caught right under the TEMP sender which has to be submersed in coolant in order to work.

The TEMP gauge, like most of Ford's gauges, isn't a true gauge. It only registers NORMAL (about the center of the gauge) when the water temp is around 190 degrees. Below 160 it stays on "C". When this is the case, you typically still get pretty good heat out of the heater.

 

[Travis Wilcox]

I was hoping you were right about air being in the system but unfortunately it must be a bad sender Napa sold me. I checked the plug by running a wire jumper between both connector ports and it went right up to reading hot, which tells me the wires and connector or working. I couldn't do an ohm test on the sender only because I couldn't get my test probes down in it without taking off the intake.