Hey guys,

I have a 1997 explorer, 4.0, automatic, 4x4, 151,000k miles, that is not shifting properly. I will try my best to give the symptoms. First of all the check engine light is on and I had it ran for codes. Came back that 3 cylinders were not firing correctly. My mechanic told me to replace plugs and wires. I did. Still not shifting properly. I will explain.

When I get on to the interstate near my home I have a hill to climb immediatly, 15-20 degree grade maybe for a half mile. Natuarally I floor it to merge with traffic. 1st and 2nd gears go through smoothly and I get up to about 50-60 mph. I think I get 3 fine as well but once I get to about 65 mph the tach reads high and the enigine continues to run at high rpm with little or no increase in speed. The check engine light begins flashing. If I back off of the accellerator a little and let the rpms fall to about 3k it then upshifts and picks up speed in the next gear. Even then though the speed is not coming on really quick like it used to. I had the transfer case replaced 2 months ago for an unrealted problem. This was happening before but I kind of dismissed it as a transfer case related symptom. See my other post for why I replaced transfer case. The tranny is only about 2.5 years old with maybe 90k on it.

The symptom occurs on flat driving as well but it is more noticable on that darn hill.

Any ideas. I put the transfer case in myself but bought it new. The "new" tranny was bought used with 45k on it. I do not think this is drivetrain related. Maybe but I was thinking vaccum or ignition realted since the codes indicate misfiring cylinders. Any thoughts?

Thanks in advance.

Joe

 

Hey Joe. It will help us to know what exact codes you are getting. 3 cylinders not firing is not a code - it is someone's interpretation of a code or codes. The code numbers have a general description associtated, then we then decipher. Now with what you have provided, that someone says 3 cylinders are not firing right, it tells me that one bank (right or left side) of your V6 has a problem. Now the only thing I know of that gives a right or left bank error is the O2 sensor. You should have 3 of them. One on the right side exhaust before the "Y" and one on the left. Third one is after the Cat converter.

So your mechanic, I think, is not too good. I think you have a bad O2 sensor that is telling the computer it is lean or rich (most likely lean from what I've seen) and then the computer (PCM) is trying to compensate. If the O2 sensor is saying lean, then it will richen up that side, right or left - it can't do one cylinder at a time because the O2 sensor looks at all 3, not one at a time. OK then, so now you have 1/2 your engine running rich - not optimal - so you will have a very noticable effect on performance - wont go up the darn hill anymore. The same performance would result if the O2 sensor gave a rich condition - running lean, not optimal, would probably cause engine pinging - which you didn't mention - so I think you are running rich.

By the way, this exact thing did happen to my 93 Explorer.

So right now you should check your new plugs. If you have 1 side looking black and sotted and the other white or tan, you probably have an O2 sensor bad.

If everthing looks OK on the plugs, get the PCM codes - Autozone will do it for you for free - or buy a scanner (cheap these days).

Your problem is not your transmission shifting incorrectly - it is doing what it should based on what power the engine is giving it.

Let us know what you find.
-JEFF

 

OK, I went to autozone and had the codes pulled. I think I misspoke earlier when I said 3 cylinders were reporting misfiring. I believe it is olny 2. Here are the codes.

po305
po306

I have not pulled the plugs yet as i just got home, its 90 degree, and I drove 80 miles. I'll let her cool down a little. I did just change the plugs 5 days ago along with the wires. A couple of the plugs were dark and a little oily, the rest were dry and had a reddish tint to them. Just like goods plugs look in the back of my Haynes manual.

Thanks again

-Joe

 

Cylinder 3 and 4 are misfiring. I would say wires and plugs but you just changed them.

I wonder if these codes are left over from before you changed the wires/plugs. Did you ever disconnect the battery for 5-10 minutes so the codes would clear? If so, then the problem is still there and the wires/plugs didn't fix it.

Were these the only codes?

There is another guy right now in this forum with an ignition problem on a 94. Same motor so I think the same set up as you. His coil keeps burning up. It's getting a wrong signal, I think, that keeps the primary open too long and overheats the coil then he loses spark to 2 cylinders. Now this makes sense since the coil pack is really 3 coils and each coil fires 2 cylinders at the same time. One a TDC and one at BDC. So the BDC cylinder, if it sees any spark at all, is not affected. Most if not all the spark goes to the TDC cylinder since it is juiced full of dripping air/fuel mixture, much less resistance than the BDC cylinder full of spent exhaust gases.

So then, curious that you have a 3/4 cylinder problem since 3/4 are both hooked up to the same coil. So you either have a bad coil, or, a problem with one of the control wires to the coil. May be simplest to replace the coil and see if that works.

Have fun trip back to Auto zone - in stock for $79.99, #C925 Wells

And what are you talking about 90 degrees? That's cold. It's 112 today in Phoenix!

 

PS - the other guy, here's the thread if you're interested, just had his engine removed/rebuilt/reinstalled. Since he's now fried 3 coils, original plus 2 new ones, we think his wiring harness was damaged with all the recent activities.

https://www.ford-trucks.com/forums/s...93#post2760993

If you have not been in the area doing someting else, then it's even more doubtful that the wiring harness (coil control wires) is the culprit.

And if you check your plugs, they probably wont tell you anything since it seems you have an intermittent miss where most of the time it fires OK. When that happens, the good fires will clean out the plugs and they probably wont look wet when you pull them.

 

If I am going to replace the coil, What about an aftermarket "stronger" coil. I have never moded this truck at all except for a sure-grip oil filter.

Is there such an item?

 

And those oil filter are the bomb!

I have not heard of a high performance coil pack - never looked for one either. No real need to improve spark out put on a stock EFI. I was just reading that the EDIS is capable of sending up to 3 sparks/cycle at low R's but not sure if ford enabled that in the hard programming.

Did you pull the plugs now that it's cooled doen to 85 outside?

 

This could be a possible Check your firing order and make sure you have not turned 3 and 4 pug wires around

 

Good thought but since they both fire at the same time anyway, it wouldn't matter. The EDIS only sees 3 coils or 3 cyclinders.

 

I have not pulled the plugs yet -- and its 82 degrees and raining. But I do have a 40 x 60 shop. Well its 9:15 est, yaaawwwwnnn!!

Those are the best reasons why I have not done this yet. LMAO

I will pull them tomorrow. I will repost then.

Thanks again for all you help.

I think we need a whole section devoted to how great sure-grip filters are.

you wrote:
"I wonder if these codes are left over from before you changed the wires/plugs. Did you ever disconnect the battery for 5-10 minutes so the codes would clear? If so, then the problem is still there and the wires/plugs didn't fix it."

I had the codes cleared this evening at autozone. Do you stick by that above statement that it could still be plugs/wires. If so is there a way to test them? What is weird to me is that under normal operating conditions they dont misfire. I do notice a little less take off power. maybe 33 1/3 percent??? j/k but there is lees power. Only when I put it under a 3/4-full throttle load does it trigger the code. This is why I was thinking vaccum. Also I had a buddy who said something of a clogged catalytic converter --- what is you experience on those. Do the fords clog often? Would this cause this symptom?

Oh yea one more symptom. It Idles a little rough.
And when I say rough I dont meaning hard but enough for an owner to notice. We've all been there, you customer hears a sound that you cant pick up or visa-versa.

thanks again and see ya tomorrow.

-Joe

 

Yeah I talked to a guy in New Jersey today who was complaining about the weather. We love getting rain here.

So I think if 2 cyclinders are not firing, even intermittently, you will have a rough idle. You're probably getting the code under full throttle because the PCM sees the problem a lot in a short period of time as you rev it up. I had this happen to me with, well not sure which problem it was. Could have been the bad O2 sensor or bad wires since I was getting the CEL before I changed either of these. But when I got on it going onto the freeway, hit 5,000 R's in 1st and 2nd, and then cruised at 60 for 20-30 seconds, the light would come on. These codes are not necessarily real time.

I wouldn't concentrate on the syptoms and surrounding conditions you may observe as much, though still very important and required, but more on what could possible cause such a condition. When you tell me cylinder 3 and 4 are not firing, and I know they fire off the same coil, then I obviously suspect the coil. Your plugs should concurr this. After some time, 100 miles maybe, you might even see the rest of the plugs get black if the O2 sensors start giving a lean code. PCM will try to richen up both banks.

Now one might contend that the coil is stupid and only does what the controls system tellsit - this is true. Maybe the EDIS (electronic distributorless ignition system) or basically the coil signal controller is bad and not sending a signal to fire. But how often does that happen? it's a solid state unit mounted next to the radiator totally hidden and protected. Coils go out all the time. Nothing special about these ones that say they should last forever - though mines gone 168K miles so I beat you

 

You may want to try and test the coil by removing the 2 plugs, grounding them out on the block and look for a spark. You'd have to remove the fuel pump fuse so the motor wont try to start. But this method may not indicate a problem if the coil issue is intermittent. I had this similar issue on my Jetski and it looked like it was firing but in fact wasn't under load. Changed the coil and it rev'ed up to 9,000 and everything was great.

 

OK Here is an update I still have not solved the issue.

I replaced..

All of the Plugs
All of the Plug Wires
The coil pack

I pulled the EGR valve off, do to some other advise, and had autozone test it and it tested good. I cleaned it up a little and reinstalled it.

It is still generating codes. The latest indicated that cylinders 1,3,5,6 were misfiring. The code book says to replace wires, plugs and coil first. Then check for vacuum leaks. I did. And then to check for faulty fuel injectors. Fuel injectors are $70 a piece. Thats like 420 for the whole engine. I dont think the injectors are bad as I have gotten a misfire code on every cylinder at one time or another in the last 2 months. I find it doubtfull that they would all be failed. And at that failing intermittantly.

ANY IDEAS WOULD BE GREATLY APPRECIATED.

Oh yea after checking around a little I did find that my muffler clamp and the engine side of the muffler was not properly tightened when installed and the pipes were loose. I tightened it up and it made not difference.

Thanks for all the help so far.

Joe

 

Always try cleaning your injectors before replacing. Pull them and fix a rubber gommet to the top with the extension straw off a can of Berrymans carb cleaner. Hook up jumpers to 12 V and then press the spry nozzel on the can of berrymans. Obviously do this over a bucket. Watch the spray and it should be a nice even fan pattern. If not, it's bad. But maybe further carb cleaner action will clean it out.

I don't think injectors are your problem. You might have a few different things going on.

I reread you first few posts and initially you had cylinder 5 and 6 misfire, not 3/4 like I thought. 5 and 6 are 2 different coils not the same one as I previously stated. So the chances of 2 or your 3 coils going bad at the same time are a bit less than having just one go bad. I am then not surprised that a new coil did not fix it.

I just read a couple other posts so here are some ideas to try. I guy had burned up one or two wires on the exhaust manifold. He just changes the wires and so did not suspect them. These engies are tight and you need to reuse all the original wire clips. And then double check there is no way the wires will rest on anything metal.

This same guy also had two loose spark plugs that he had just replaced. So enough said about those mechanical aptitudes.

Another guy actually had a new plug that had a cracked and arcing ceramic insulator. Recheck you plugs. New does not mean good.

On other control issues - EGR. How do you check one at auto zone? The valve is one thing but it is an actuator, not a sensor or feedback to the computer. The valve operates open loop. It goes open/closed based on the vacuum actuators solenoid response to the PCM's signals. There is a DPFE pressure sensor that tells the PCM how much exhaust gas is flowing into the engine. This is a control signal that the PCM tehn reduces fuel flow to the engine - with high exhaust flow. Make sense? Exhaust has no/little air so engine needs less gass to maintain A/F mixture - good for gas mileage right? I have heard these DPFE sensors going bad and causing all kinds of havock from idle through cruise speeds. However, this shouldn't throw a cyclinder misfire code.

Other component not discussed is the IAC - idle air controler. If bad it can easily cause a bad idle. It's effects are less at higher RPM's but it does respond open/closed to various other engine conditions beside being at idle. these can be cleaned by disassembly.

Another item is the MAF sensor. These get dirty pretty fast. I recently checked my maintenance records and it looked like the dealers were replacing mine about every 25-30K miles - warranty what did I care? These can be cleaned too. Check here http://draco.acs.uci.edu/explorer/
But typically dirty ones cause a lean engine condition and to the point of pinging heavily. You might be getting loss of power from this but not enough yet to ping. Man the first time I cleaned mine I couldn't believe the power that I was missing.

Your muffler bearing being loose doesn't really affect engine performance. It's not like the exhaust will suck in air and throw off the 02 readings. Exhasut is always under constant pressure and leaks only cause excessive noise.

But then again, when did you last change O2 sensors? I had a new one go bad in less thatn 20K miles. Might be prudent to change those buggers anyway. Couldn't hurt.


So there are a few things to look at. See what you find and repost results along with the actual code numbers. And as always, when changing or cleaning any of the PCM controled or feedback components, disconnect the battery for 10 minutes to remove the learned correction factors. If you make the engine all new a perfect again, you need to tell the PCM such and then it won't try to correct for a bad condition that is not there.

 

Forgot. Cat problems won't throw codes either. No tie whatsoever to the controls system. If it were bad/breaking down, the honeycomb inside would be rattling around. Ever stick a bannana into a tale pipe? Wait - that was Eddie Murphy. Anyway, the loose honeyocmb turns sidesways and blocks air flow - engine wants to die. When these go bad it's either a quick boom, boom, boom and everything blown out the exhaust or it could be a longer term but very intermittent issue. The truck will jerk back and forth violently and then the honey comb moves around and exhaust flow is restored and everything is happy until it does it again.