4.0L with OHV and random misfires on all cylinders

[Sndsational]

So I continue to be at a loss...

I went ahead and did a fuel pressure test. 64psi and holding. according to the book, that is within normal limits. I really cannot think of anything else that is causing the problems I am experiencing.

One thing that I did notice is that it ran like crap yesterday when I was coming home from work. Then when I was at my father's house last night and took him for a ride to show hime the issues, it seemed fine and my dad said "that seems normal to me". Got in it today...seems to be running like CRAP!!

I cannot think of anything else. Possible that the computer needs to be "flashed"? I think I have a leak at the exhaust manifold....would that create an issue? Also, I believe I said it earlier, but the mechanic thinks that it could be the valve seats not sealing completely....possible. I was considering new bolt on heads with new valves and everything....think it will fix it?

I really need your continued support and thank you to all those that have contributed.

 

[2000StreetRod]

temperature related?

Is there any indication that the power loss is related to engine temperature? Does it run better when cold started vs warm started? If the engine loses power after a warm start you may have a bad engine coolant temperature (ECT) sensor. The PCM enriches the fuel mixture at engine start. If the ECT sensor erroneously reports the engine cold when it is actually warm then the mixture will be excessively rich and the engine will misfire. The ECT sensor is independent of the engine temperature sender that drives the indicator in the instrument panel.

 

[Sndsational]

I recall there being some question on cold start vs. warm start and such. It is possible. It is a 17.00 dollar part at Autozone, so it is worth the shot at wedding it out. You never know. Yesterday, the ride with my father occured after a 25 minute highway commute, to the engine was warm. This AM, the engine started cold and also seemed to have taking a "little bit" to get started. I will keep you advised.


Thank you 2000 street rod !!

 

[budwich]

hmmm ... I don't think you answered the question about "checking / reading your plugs"... do they all look similar and what do they look like. The mechanics's "valves story" seems kind of funny since you reported "all cylinders have random misfire" -> all your valves have issues... OK..... if that's true... simple check would be a compression checks on all cylinders.... that check should be done anyways to rule out "major" mechanical issues.

 

[Sndsational]

so there i was......taking my new coolant temp sensor and trying to install it. when all of a sudden, POOF, the pressure I forgot to relieve sprays molten anti-freeze all over my arm. Yup, 1st to 2nd degree burns! OUCH!

The kicker is I was taking out the temperature switch instead.....YUP, wrong part! So, my assumption in that I can take out the temp sensor now without worry that it will explode over me? pressure should be gone??? Just want to make sure. I am running out of unburned skin!!

 

[Sndsational]

Well, it looks as thought the coolant temperature switch made a HUGE difference in the performance and response of the truck. I took it out and it actually had a "film" on it....almost like a red color. Anyway, it seems to have made a difference and the shifts have smoothed out some. I do believe however, I still have a pretty significant exhaust leak at the manifold....thus creating some back pressure issues and again leading to decreased performance. Any thoughts or feedback.


BTW. Thank you 2000streetrod. Your info was a big help.

 

[2000StreetRod]

Exhaust manifold leak

I doubt that a leak in your exhaust manifold would result in an increase in back pressure. However, it might affect your O2 sensor readings which could impact your air/fuel ratio. The leak should be fixed even if it's not the cause of your performance problem.

 

[Sndsational]

Ok, so continuing on my battle to get everything running well on the Explorer, I found that is is still not 100%. Last night driving home, it was banging and clunking and seemed to be shifting eraticly. Alot of the banging I have been told is "backlash" in the differentials. Could this be possible? It is usually loud. Also, ar ethe explorers known for having a loud downshift....like the linkage makes a slamming type noise when it downshifts?

Additionally, performance wise it is better than before but still not 100%. I think I am going to investigate the timing, but also I think I need to look into the functionality of the fuel injectors. I think there may be one that is not firing right all the time. Any advise on how to test without getting deep in to the engine?

 

[Car-Dog]

Have you had the drive shaft greased? i know that in the 98's that was a really big problem, run low on grease and the drive shaft splines start catching and slipping.

 

[Sndsational]

can you tell me how I would do that? The greasing of the driveshafts?

 

[Car-Dog]

http://www.explorerforum.com/forums/showthread.php?t=106307&highlight=grease+driveshaft

I can't but, this thread sure can.

 

[Sndsational]

When you say crease the driveshaft, do you me the shaft running fron to back or the half shaft axles from the front differential to the wheels?

 

[Car-Dog]

front to back

 

[Sndsational]

Ok, so I went ahead and greased the spline on the driveshaft and found that it helped. I used wheel bearing grease....hope that is ok?!?!?!

Also, while doing this, I figured I would look for the elusive exhaust leak I kept thinking I had! Sure enough, I found it. It was right on the pipe between the dual cat converter setup. It seems the stress from the hanging rod pulled the weld and "ripped" the pipe. Good thing the converter was still under it's 5 year warranty! Hopefully that will address much of the performance issue I have been having.


My next question for you all is: Does anyone have info on how easy it is to replace the heads on the OHV 4.0L? I am looking to maybe do it in the near future. My passengers side head cracked at the bolt hole for the manifold pport and I have a leak there. My thought is that when I am ready, I am just going to replace both heads (with bolt ons that have new valves, seals and everything else), the manifolds and anything else that is easy that will help gain longevity of the motor.

In any case, please advise.....your input is appreciated.


Thank you

 

[joe doe]

i just had the whole top end of my 4.0 ohv regasketed.i can tell you how much i paid for all the ford gaskets for the job .

the ford gasket kit for the top end was 208.00 plus tax .thats everything to tear it down to the heads.

the head bolts were 3.50 each or about 56.00 for them all.you do not reuse the old bolts on the head .you buy new ones .

my mechanic charged me 500.00 labor to tear it down to the heads and replace all the gaskets .

mine was leaking antifreeze everywhere so i needed this done.
total job with oil change was about 800.00

now if your doing it yourself you can save the 500.00 in labor .

 

[Sndsational]

At a serious loss!

Ok, I have basically had enough of my truck. It is running rough...again and it seems to be skipping, or misfiring. Reving the engine to about 5000RPM, it seems to be skipping bad. Sitting at idle, it is definately rough and the motor is "bouncy". For those of you that have been following this thread, you know a bit of the history of the truck.

I cannot stand it anymore....even the mechanics cannot give me a definate cause and I keep paying diagnostics on this for them to tell me I have a problem. Gee....thanks, I did not know that! How about giving me the solution.

Anyway....I really need help. It is affecting the driveability in that the shifts seem to want to compensate for something. I NEED HELP!!

Just an FYI no CEL.

HELP!

 

[2000StreetRod]

Compression test

I looked back thru your posts and saw no mention of a compression test results. If one has been done, what were the results? If one has not been done, I suggest you do one.

Also, make sure that your EGR valve is not sticking open. The valve should be closed at closed throttle or the engine idle will be adversely affected.

Engine misfire is normally the result of ignition, injection or compression malfunctions in that order. You've replaced most of the ignition components. How old is the fuel pump? It could be intermittent - especially if you have been negligent in replacing the fuel filter. When was the fuel filter last replaced? Have you added a bottle of fuel injector cleaner to the tank?

 

[Sndsational]

2000StreetRod, can you tell me how I would do a compression test? Never did one before. Also, how do I check the EGR valve? Mine had been changed a few years back, but that of course is no guarantee of anything. The fuel filter has been changed in the last year or so, but befor that never have I done it...I have owned the truck for 5 years. I tested the fuel pressure and it was fine.....64psi. What about a bad injector.... could that cause the computer to compensate with more fuel to other cylinders causing a misfire?

My other question to you is regarding the transmission. I noticed that you have the 5R55E like I do. Mine is recently installed as a remanufactured tranny.....I find it to have very firm shift....and also downshifts rather firm almost banging, but not really a violent bang. Is this normal for these transmissions? I know that over the years they have had upgrade kits and such....any thoughts?

 

[2000StreetRod]

Compression test & EGR valve

2000StreetRod, can you tell me how I would do a compression test? Never did one before.

The test can be performed with all of the spark plugs removed or just one at a time. The throttle plate must be held wide open. Disconnect the electrical connector at the coil pack coming from the PCM. Screw a compression gauge adapter into the spark plug hole for the cylinder under test. Crank the engine with the starter motor for at least 3 compression strokes and record the highest reading on the gauge. While you have the spark plugs out check them for abnormal indications.

Also, how do I check the EGR valve? Mine had been changed a few years back, but that of course is no guarantee of anything.

See My Helpful Thread EGR System O&T

The fuel filter has been changed in the last year or so, but befor that never have I done it...I have owned the truck for 5 years. I tested the fuel pressure and it was fine.....64psi.

Your fuel pressure reading is good but the pump could be intermittent. That is a very difficult thing to troubleshoot. The PCM has no way to monitor the fuel pump. You have to monitor the fuel pressure while driving or the current flow to the pump. You might check the condition of the electrical connector at the left frame rail forward of the fuel tank. Sometimes just disconnecting and connecting the connector will clean the contacts. Replacing the fuel pump is a pain. I would eliminate other possible problem sources first. Then I would run a line from the Schrader valve to a gauge mounted where you can watch the pressure while driving to determine the pump is faulty before replacing it.

What about a bad injector.... could that cause the computer to compensate with more fuel to other cylinders causing a misfire?

The PCM monitors the power output of each cylinder and if one varies significantly from the others will usually set a diagnostic trouble code (DTC) for a misfire. If it were compensating by increasing the richness of one bank for a bad injector then a too rich DTC may not get set since the O2 sensor output for that bank may look normal. See if a bottle of fuel injector cleaner helps any. I only use Techron. Some inexpensive fuel injector cleaners result in deposits on the valves.

My other question to you is regarding the transmission. I noticed that you have the 5R55E like I do. Mine is recently installed as a remanufactured tranny.....I find it to have very firm shift....and also downshifts rather firm almost banging, but not really a violent bang. Is this normal for these transmissions? I know that over the years they have had upgrade kits and such....any thoughts?

The softer the transmission shift the more the wear on the components. Soft shifts result from the overlap of both gears being engaged at the same time. A good transmission shop will upgrade the transmission when it is rebuilt to improve reliability and reduce wear. The transmission shift solenoids are controlled by the PCM. I have a custom tune to optimize my shift points and firm up my shifts.

 

[Sndsational]

Awesome, thank you for the help....I will investigate and let you know how I make out.

As far as the injector cleaner....can you add it any time to the fuel or should I wait to empty the tank and then add iot prior to a fill??

With the fuel pump test...is it safe to be driving with the gauge connected?