1999 Ford Ranger 2.5L Ruff Idle, Missfire Codes, No Power

Got a 99 Ford Ranger with a 2.5L engine which is a 4 cylinder with (2) 4-wire coil packs, 8 spark plugs and 8 wires. Starts up no problem. Runs rough at idle but will smooth out after pressing the gas pedal down about an inch. Drove it through town and ran rough from stopped at red light up until about 35mph. Got onto the highway seemed to pick up speed fine and running good at highway speeds. Got off of highway and started up a hill and couldn't do more than 10mph even with the pedal to the floor.

Ran the OBD2 test and showed misfire codes for cylinders 2 (PO302) and 3 (PO303) which on a 2.5L the cylinders are numbered in a straight line and in numerical order starting with 1 in front of engine and so ending with 4 in the back of the engine.

Previous owner never did a tune up in the 100,000 miles he put on it and so I checked the coil packs first but all 8 are firing properly. Replaced all 8 plugs and wires with Ford Motocraft and it still runs the same way.

Didn't notice any antifreeze in the motor oil or motor oil in the antifreeze. Cleaned the MAF sensor and didn't find any vacuum leaks.

So why would it run rough at idle, run smooth at higher speeds, lack power on hills, and codes only show misfires at cylinder 2 and 3?

At my wits end and really need help since this is our only vehicle and only way to get anywhere. Can't even drive it to a garage if we could afford the cost of the repair(s).
 
Compression check will show you a leaking headgasket between 2&3. When your engine sets after a drive and shutoff, a small amount of antifreeze is introduced into those 2 cylinders. When starting or at idle the engine needs to burn that antifreeze out of the cylinder and clean the plugs. Had the same problem on a Nissan Altima last summer.
 

That's what I was afraid of it being a head gasket. Odd thing is coming from my experience, whenever I've had a head gaskets blow before, the engine didn't run good at idle or at highway speeds. Hmmm maybe just how newer vehicles are. I love my older Ford Truck that has the good ol' 300 straight 6 engine... long running engines, easy to diagnose, and SUPER EASY to work on since there isn't all of the newer electrical/electronic stuff on it... just a carburetor, distributer, and electronic control module which I have a spare module mounted to the truck and so if I have firing problems, all I gotta do is unplug one control module and plug in the other!
 

Thanks. Looking it up right now. You and some of the posts from other sites are mentioning cam positioning sensor. Will get back to ya as soon as I'm done going through the shop manual and going thru the search results on the web
 
I'm a little perplexed as to why the suggestion about a blown head gasket? Is it losing coolant? If it IS, then by all means I would do a
compression test and probably suspect a gasket leak.... but if it's not I would not be inclined to think in that direction although doing
the comp check is still a good first step. From my observation over the years the Ford 2.3 was a pretty tough long lasting low maintenance
engine not terribly prone to head problems.... and I don't see why the 2.5 would be any different as it's just a taller version of the same
thing.
What I WOULD be inclined to look at is the fuel pressure. Is it making 35 pounds at the schrader valve on the rail? If not I'd change the
filter under the cab along the frame rail. Your problem really stinks of a fuel pump on it's LAST leg. I had 2-3 of them go bad on a 3L
Ranger and that was universally how they went bad until the time it just wouldn't start. So that's where I'd be focused but certainly
you're out nothing to do the comp test to rule that out or verify it if it is a problem.

Rod
 

Makes sense to me too that it most likely isn't a head gasket since it runs rough at idle but yet runs pretty smooth at highway speeds, but yes a compression test is possible in the near future if I can't figure out anything else. Only thing is that #3 cylinder which needs tested, isn't going to be easy getting the compression tester's hose ran down to the hole in the head. Since we're on the subject though, so where do I test compression when an engine has 2 spark plugs for each cylinder?

Concerning the fuel pump... I was curious how a fuel pump would cause rough idle but then start to work better as more gas was applied and also keep in mind based on trouble codes being shown, the fuel pump would only be effecting cylinders 2 & 3? I have even cleared the codes and then checked them again to find that the same codes/cylinders showed up as being a problem.

Oh and I also checked the fuel injectors as this seemed like a possibility but all 4 checked ok.
 

Yes the 2.5L definitely has a camshaft positioning sensor. I also called 3 different part stores including NAPA and I was told that their computers show this vehicle as having one.

So another curious thing about the symptoms on this truck and a camshaft positioning sensor is how does this sensor go bad or go bad enough that it only causes misfires in 2 of the 4 total cylinders? If it goes bad or is going bad, wouldn't it cause misfires in all cylinders?
 
I suspect blown head gasket, especially if it is blown between cylinders. It can leak between cylinders and not involve the coolant leaking. Also it will start out as a small leak that is only noticeable at idle, then progress to a major loss of compression for both cylinders, which it probably has done by now.

A compression test will only reveal a major gasket problem. But if it is blown to the point of loss of performance, it should show low compression on the 2 center cylinders. To test, just remove one plug (the easiest to get to) per cylinder, prop the throttle open.
 

Ok. Will give it a try but gotta wait till a little later on this evening... like around most of our country, it's on the 90's here in Ohio.

So when an engine has 2 spark plugs per cylinder, which one do I use for a compression test or am I supposed to test both of them?
 
Both plugs go to the same chamber, so the easiest to get at is just fine. Swap injectors from hole to hole to see if the issue follows the injector. (how did
you check them in the previous post? Jim
 

I followed what our local shop said they do which is to use a long screw driver or pry bar. Hold it to cylinder 1's fuel injector and with your ear held against the handle of the screwdriver/prybar, listen to the clicking/pulsing while at idle, mid throttle, and then high throttle. Said I should have a constant clicking that increases as gas is given and rpms increase, and for me to check all cylinder's fuel injector this way and then compare all of them. If all of them are the same and no signs of erratic clicking or such, then shouldn't be the injectors. If misfires are only showing up on cylinders 2 & 3 but yet injectors sound the exact same as cylinders 1 & 4, then no reason to be the injectors. If injector were clogged, then poor performance would be noticeable at both low and high rpms and so I am curious how if a injector is bad or is going bad, then how does it perform poorly at idle (lower rpms) but then can work better or fine at higher rpms.
 
It still sounds like an ignition problem to me.

The ranger has a wasted spark system, same that's on my Focus. The spark fires on both the compression and exhaust stroke on
each cylinder.

And the way the cylinders are tied together in the coil(s) are 1-4 and 2-3. You are getting misfire codes on 2-3, which are
common on both coils. My understanding of the dual coil/plug setup is one of the coils is slightly delayed, giving a longer
total spark duration...so maybe one of your coils feeding one set of plugs is bad/weak on the 2-3 cylinder side.

If you still have your old plugs, you could try pulling the plug wires from one coil off the plugs on cylinders 2 an 3(leave
the plugs in the head), stick your used plugs in the wires, lay or clamp them against something on the engine to give you a
ground(no oil or gas in the general area, don't need to burn your truck up), see if you've got a good spark. If yes, try the
other wires from the other coil. Shoot, if you pull off good sparking wires you should feel/hear a difference.

Make sure the 3 prong connectors feeding the coils are in good shape, seen them fall apart/ go bad before too, causing a
misfire on 2 cylinders.

Don't know if this will do you any good, but checking this stuff wont cost you anything.

Good luck

Fred
 
(quoted from post at 18:57:23 07/23/16)
While you are replacing the head gasket goat head and replace the injectors, the injectors are more than like your issue.

http://www.injectors4u.com/

Hmmm, don't think I said or implied that I am replacing the head gasket...still have to do a compression test to narrow things down.

Concerning the injectors, I followed what our local shop said they do which is to use a long screw driver or pry bar. Hold it to cylinder 1's fuel injector and with your ear held against the handle of the screwdriver/prybar, listen to the clicking/pulsing while at idle, mid throttle, and then high throttle. Said I should have a constant clicking that increases as gas is given and rpms increase, and for me to check all cylinder's fuel injector this way and then compare all of them. If all of them are the same and no signs of erratic clicking or such, then shouldn't be the injectors. If misfires are only showing up on cylinders 2 & 3 but yet injectors sound the exact same as cylinders 1 & 4, then no reason to be the injectors. If injector were clogged, then poor performance would be noticeable at both low and high rpms and so I am curious how if a injector is bad or is going bad, then how does it perform poorly at idle (lower rpms) but then can work better or fine at higher rpms.
 
The extra plugs and coil are for emissions purposes only, these are on the intake/LH side of engine and the plugs are fired on exhaust stroke to help burn fuel before it enters the exhaust. If you want to eliminate the ignition system ( RH or rear coil, plugs and wires) you can simply rearrange the firing order on the front coil so the plugs on the intake side will fire on the compression stroke. Some people have done this mod and claim slight power and economy gains YMMV. If you do this mod, and engine runs smooth, its probably safe to say the back coil is bad, or wires/plugs on RH side.

Mark the plug wires with cyl numbers or something to make it easy to identify or switch back later. swap the pattern with the one mentioned below.

Before
4 2
1 3
After
1 3
4 2

Pic for reference
2008-06-08_020732_92714683.gif
 
I can not explain it but my 2003 was doing something close to what you are saying, it drove me crazy until someone suggested cam positioning sensor. Replaced that and problem was gone.
 

Don't know other than seeing as folks had you headed in that direction injector issues on those are difficult to diagnosis unless its DEAD . Driveabilty issues on those engines put up a good fight.

I take it you replaced the fuel filter.
 
(quoted from post at 20:50:40 07/23/16) The extra plugs and coil are for emissions purposes only, these are on the intake/LH side of engine and the plugs are fired on exhaust stroke to help burn fuel before it enters the exhaust. If you want to eliminate the ignition system ( RH or rear coil, plugs and wires) you can simply rearrange the firing order on the front coil so the plugs on the intake side will fire on the compression stroke. Some people have done this mod and claim slight power and economy gains YMMV. If you do this mod, and engine runs smooth, its probably safe to say the back coil is bad, or wires/plugs on RH side.

Mark the plug wires with cyl numbers or something to make it easy to identify or switch back later. swap the pattern with the one mentioned below.

"you can simply rearrange the firing order"

Are you saying to swap the plug wires from the rear coil pack (exhaust firing coil) with the plug wires from the front coil pack (intake firing coil)?

If so, I would love to know how this is done simply... both the Ford Motorcraft exhaust firing wires that were on it and the higher grade aftermarket wires we replaced them with, will not even come close to reaching the front coil pack. They are anywhere from 2-3 inches from being possible to connect them from their original position of being on the rear coil pack to then be moved to connect to the front coil pack. This is even with me trying several different ways to route the wires in order to get the maximum reach to the front coil pack.
 
(quoted from post at 06:28:38 07/24/16)
Don't know other than seeing as folks had you headed in that direction injector issues on those are difficult to diagnosis unless its DEAD . Driveabilty issues on those engines put up a good fight.

I take it you replaced the fuel filter.

"Drivability issues on those engines put up a good fight."

YOU ALMOST HIT THE NAIL ON THE HEAD! I WOULD ONLY CORRECT IT BY SAYING THEY PUT UP A KILLER FIGHT... THIS IS JUST COMPLETELY RIDICULOUS AND I KNOW THAT FORD ISN'T THE ONLY CULPRIT! ALL MAKERS OF VEHICLES ARE GROSSLY IRRESPONSIBLE TO MAKE SUCH JUNK. WHAT THEY'RE DOING IS MAKING IT SO MOST EVERYONE CAN'T DIAGNOSE & WORK ON THEM THEIRSELVES THUS ARE FORCED TO PAYING THE GARAGES AN ARM N AN LEG TO DO IT!

Concerning the fuel filter, how would a bad fuel filter only cause 2 cylinders to misfire? If a fuel filter is bad (clogged up), it limits the amount of gas going to all of the cylinders. I wouldn't even be able to guess at how a bad fuel filter could only allow enough gas to cylinders 1 and 4 to let them fire properly but won't allow enough gas to cylinders 2 and 3 in order to allow them to fire properly.
 

Have you ever replaced the fuel filter if not its due way pass due its not money trowed away.

I an not there to get a seat of the paints feel for your issue if I were I could make a more educated GUESS from far far away with little info to go on.

The fuel system is a EZ check if you have a fuel pressure gauge, pressure, volume and fuel quality.

Its a process of elimination.

You are right the wires are a Taylor fit I never thought to try that trick it may be doable but its gonna take some work to get them rerouted are relocate the coil.
 
I would run a compression test if 2 and 3 misfire, they are also firing at the same time, but on alternate strokes.
 
pull 2 and 3 spark plug and spray a bunch of wd 40 in one cylinder. Not enough to hydro lock it. put the spark plug loosely in that hole, disable the coils and crank it
over. I'm going for a blown head gasket between them and if so, the wd 40 will blow out the open hole.
 
(quoted from post at 15:03:36 07/24/16)
Have you ever replaced the fuel filter if not its due way pass due its not money trowed away.

I an not there to get a seat of the paints feel for your issue if I were I could make a more educated GUESS from far far away with little info to go on.

The fuel system is a EZ check if you have a fuel pressure gauge, pressure, volume and fuel quality.

Its a process of elimination.

You are right the wires are a Taylor fit I never thought to try that trick it may be doable but its gonna take some work to get them rerouted are relocate the coil.

Well and I'm not going to spend unnecessary time and money on parts that don't need changed to fix the problem. If someone doesn't care about working in the 90 degree and up weather plus has extra money to just replace things that won't diagnose or fix the problem, then more power to them.

Makes no sense to spend more time and money on other things instead of getting to the POINT OF THE PROBLEM to fix it... and then after seeing if it is going to be a reliable vehicle, definitely go around and replace those other things a little at a time.

Concerning rerouting/relocating the plug wires from the back coil to the front coil, there is no way! Simply won't reach NO MATTER how they are routed at least not with the factory original motorcraft wires or the higher quality aftermarket wires we bought.
 
(quoted from post at 16:01:14 07/24/16) I would run a compression test if 2 and 3 misfire, they are also firing at the same time, but on alternate strokes.

I agree with you and other concerning to do a compression test. Going to be a big pain having to get to get to some of the spark plugs again but the compression test will help greatly to narrow down the problem.

I'm still having problems with KNOWING FOR CERTAIN which plugs to remove to perform the compression test: Haynes manuals are most often worthless when it comes to getting a direct answer, so far I've gotten 3 different replies from part stores which by the way are pretty much employed by college students anymore who are lucky if they even know which side your gas lid is on, and even here on these forums I haven't had a consistent answer. Going to call the local garages to see if they can give the same answer as the next.
 
I would suggest you not get too tied up in the 2-3 'misfire' in terms of what the 'codes' are telling you. From my limited understanding of
OBDII on those things.... the codes don't give you much more than a general idea of where to look. A code is not the be all, end all
diagnosis of the problem.... so just go back to fundamentals. If it hasn't had wires, plugs and a fuel filter in a while, you go ahead and
change them anyway so that you can rule them out as a problem. I'd be willing to bet if you take it to a garage that is the first thing they
will do too.......
Checking the fuel rail pressure would be my next step at this point. Sacrifice a cheap tire gauge and see what it's got...
Not knowing the internals of the injectors specifically I can only speculate.... but I would bet they have an internal check valve... and if
they're poor... they may not get charged properly or fire properly. Lots of weird little things can happen...

Rod
 
(quoted from post at 19:15:09 07/24/16) I would suggest you not get too tied up in the 2-3 'misfire' in terms of what the 'codes' are telling you. From my limited understanding of
OBDII on those things.... the codes don't give you much more than a general idea of where to look. A code is not the be all, end all
diagnosis of the problem.... so just go back to fundamentals. If it hasn't had wires, plugs and a fuel filter in a while, you go ahead and
change them anyway so that you can rule them out as a problem. I'd be willing to bet if you take it to a garage that is the first thing they
will do too.......
Checking the fuel rail pressure would be my next step at this point. Sacrifice a cheap tire gauge and see what it's got...
Not knowing the internals of the injectors specifically I can only speculate.... but I would bet they have an internal check valve... and if
they're poor... they may not get charged properly or fire properly. Lots of weird little things can happen...

Rod

Please go back through the replies... spark plugs and plugs wires have already been changed. With all due respect, it doesn't help much if people are going to keep suggesting to do things which has already been done and didn't fix the problem.

Still need to know how a bad or starting to go bad fuel pump that's creating low fuel rail pressure, would cause cylinders 1 and 4 to run fine but cause cylinders 2 and 3 to misfire.

Also still waiting for certain people to respond back as to how a clogged fuel filter would cause cylinders 1 and 4 to run fine but cause cylinders 2 and 3 to misfire.

Oh and I'm not saying you're full of it... I simply want an explanation as to how those things would cause the problems I'm having before I would spend my time doing the work to check them.
 

Hobo,NC
Tractor Guru
said "I forget to write down folks names I should not reply too... Sorry for the inconvenience."

David G
Tractor Guru
said in reply "Huh?"

Just gotta ignore Hobo. Me and my wife already had the unfortunate situations of having to deal with him on the N-series discussions as well concerning our 8n and 9n tractor. Many times even when you politely question his advice, his responses let ya know to just not respond back to him and try to keep focused on the point of the problem your having with your tractor
 
(quoted from post at 19:58:45 07/24/16) I really think you either have a head gasket or coil pack issue, those are both common to 2&3.

Hi David,

I seriously think you're right on the head gasket especially when the more and more blogs, videos, etc etc I keep coming across are pointing to the head gasket.

I gotta rule out the coil packs though... I just got back inside a little bit ago from changing both coil packs and I still have the same problem. Even tried switching the coil packs just incase advanced auto gave me one that was doa right off of the shelf since it has happened to us before
 
OP, you probably have a couple of problems; rough idle from a filthy throttle body. Partially clogged fuel filter for the lack of power. If the guy that you bought it from never did the plugs in 100K miles, I doubt he replaced filters or cleaned throttle bores. If the fuel filter is clogged, that stresses the fuel pump and that will start failing. No power.

If you really do have a head gasket leaking, the plugs from 2 and 3 should have looked a lot cleaner than the plugs in the other holes. The water flashing to steam blasts the carbon off everything in the cylinder, so it looks like brand new.

20 years ago the cars and trucks got complicated enough that the typical DIY isn't going to be able to diagnose what's wrong without a lot of throwing parts at it and hoping to fix it. I was a Ford dealer tech, and the factory schools made a point of explaining the trouble code is a rough indication of where to look; it's not instructions to replace an exact part.
 
Read my post again, carefully. I didn't mention swapping the plug wires between the front and rear coil. You are simply swapping the order on the front coil only. Front wires stay on front coil you are just moving them around on the coil.

If you want, you can swap the coils too, the front coil, plugs and wires are not even needed for the engine to run.
 
I missed one of your replies about checking the coils. It's probably time to do a compression test. Obviously the exhaust spark plugs are easiest to remove so I would check em there.

Compression spec for the 2.5 should be somewhere around 150psi. I wouldn't want to see more than a 20% difference between all cylinders and usually misfires start showing up around 10-15%.
 
(quoted from post at 22:31:55 07/24/16) Read my post again, carefully. I didn't mention swapping the plug wires between the front and rear coil. You are simply swapping the order on the front coil only. Front wires stay on front coil you are just moving them around on the coil.

If you want, you can swap the coils too, the front coil, plugs and wires are not even needed for the engine to run.

I missed one of your replies about checking the coils. It's probably time to do a compression test. Obviously the exhaust spark plugs are easiest to remove so I would check em there.

Compression spec for the 2.5 should be somewhere around 150psi. I wouldn't want to see more than a 20% difference between all cylinders and usually misfires start showing up around 10-15%.

Sorry I misunderstood what you said about rearranging the spark plug wires on the front coil only.

Concerning compression test I am a bit confused. You're saying that the front coil pack, plugs and wires are not even needed for the engine to run (these got to the intake side or the right side of the engine while facing it from the front of the truck) but saying to do the compression test on the exhaust spark plugs since they are easiest to remove. The easiest spark plugs to remove are on the left side of the engine while facing it from the front of the truck and are controlled by the rear coil pack. So if the front coil pack controls the intake spark plugs, then how is it that they are not needed to run the engine? How is it that the exhaust spark plugs are the primary spark plugs needed to run the engine? I would have thought that igniting spark on the intake side would be what mainly fires the engine and then igniting spark on the exhaust side would be what burns up any left over gases as they leave the exhaust.
 
Well I possibly learned something here on these 4 cylinder 2.5L engines which have 2 coil packs, 8 plug wires, and 8 spark plugs.
The exhaust side spark plugs are used to create combustion. The intake side spark plugs are fired on the exhaust stroke to reduce emissions by burning unspent fuel.

So if this is true (I can't find verify yet since Haynes manuals are some of the most poorly explained information out there being so vague or even not containing what is commonly needed to know things), then it seems to make sense as to why you can do a compression test from the exhaust side (left side) of the engine.

So whatever happened to the good ol' Chiltons manuals? Me and my dad still have them from the 1970 and 80's for our trucks. I mean wow do they go into detail and show so much better pictures that are DIRECTLY related to the make, model, and year of vehicle you're workin on. Haynes indulges in cutting corners by giving half-azz info like showing pictures of where sensors are located for engines that have nothing to do with your particular engine and then saying the sensor should be located in the same general area, but even when you have the manual sitting on the radiator and looking at your engine, it's quite obvious that the sensor on a say 3.1L is located in a completely different location than the engine you have and no matter what section of the manual you go, they do not show the location of the sensor for your engine.
 
(quoted from post at 16:15:27 07/25/16) Well I possibly learned something here on these 4 cylinder 2.5L engines which have 2 coil packs, 8 plug wires, and 8 spark plugs.
The exhaust side spark plugs are used to create combustion. The intake side spark plugs are fired on the exhaust stroke to reduce emissions by burning unspent fuel.

So if this is true (I can't find verify yet since Haynes manuals are some of the most poorly explained information out there being so vague or even not containing what is commonly needed to know things), then it seems to make sense as to why you can do a compression test from the exhaust side (left side) of the engine.

.

Either of the plug holes can be used to do your compression test; use the better access one. I did a little research on Ford twin plug heads, one engine was set up to only fire the exhaust side plugs when the temp was down around zero. The coolant temp sensor tells the ECM how cold it is, and once the engine warms up a bit, then it starts firing both plugs.

The twin plug on your engine does not throw a second spark to 'burn' the exhaust gases. Unless you had a misfire in that cylinder, there's nothing left to burn if the first plug did it's job.

In the past, twin plug heads were to start the flame front in two places at the same time. That tends to eliminate pinging or detonation of the fuel. So they raise the compression ratio to gain some more power and fuel economy. That's the most likely reason for the twin plugs on your Furd...
 

As in the post you refer to we can only go by the info you provide. I wish there were a silver bullet for every issue but most of the time its not and you have to gather the info to eliminate and narrow down the suspect.

I peacefully bowed out for some reason you feel the need to babble on. In the post that got y'alls drawers in a wad the answer to your question was in the description of your problem y'all typed out not me I ask that you go back a read what you wrote.

I will gladly return your money for my service look for it in the mail.
 
Some reading material for you... pay particular attention to the section that talks about 'Lean misfire' as it would tend to describe your
condition.

Rod
OBDII codes
 
This may sound some what stupid, but I bought a 1998 Ranger with the 4.0. It ran just like what you are describing. So the first thing I did was to replace the plugs and wires. Not much change, so I replaced the coil pack. No better. Fuel filter, new oil and filter didn't help. Ends up that the last time the little truck was tuned- up somebody put the wrong spark plugs in, and I didn't do any research, just bought the same plug that came out of it. I installed the correct spark plugs and the problem wen't away.
 
Hey all.
Thought id chime in here because i just spent 3 weeks and more money than i care to admit on the same problem. Pull the pcm out, take the cover off and see if the electrolytic capacitors in there have leaked out on the circuit board or if any of their leads are burnt off. Cost me $ 0.0 to fix the actual problem after i found it. Had capacitors in my spare parts bin, a little soldering and my problems went bye bye!
If thats the problem maybe easier for you to get a new one. Dont know how well you are with soldering on a pc board. But you will definately be able to see the bad/burnt components on the board if they failed. Its an easy visual check. Do it while your still sane!

Hope that helps ya! later
 

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