My 2.3L has about 145k miles on it. A few years ago I was getting about 25mpg and it ran quite well. Over a period of time the mileage dropped, I noticed less power and in the last year it has began to run poorly. When idling it feels like I get a misfire every few seconds (although the code reader often won't show a misfire), and when cold and moderately accelerating it will cut out a fair amount. Then even when fully warm it just seems under powered and when accelerating under load it doesn't acceleration smoothly, but feels like it is cutting out some. Kind of like an old carbeurated engine might do before it warms up. The code reader will register some misfires (but less than I would expect), but there are no codes or obvious issues there. Also at times when driving and I am coming to a stop, I will push in the clutch and the engine will just die. Then I might start it and it dies again. Then start it again and it is fine. But this isn't that often. Driving to work last week I was on a leave stretch at a steady 65mph and it just starts shuddering. As if the ignition was cutting in and out very quickly. I pushed in the clutch pedal and it continued to do it for 3 or 4 seconds then just cleared up.

I have used a fair amount of seafoam, I have inspected the coil pack, plugs and wires and they look good. I have replaced the fuel filter, I have checked fuel pressure with key on engine off and key on engine running and it is fairly steady at 65 psi and it will hold this pressure for quite a while after the engine is stopped. The valve cover gasket does need replacing as it leaks all around the perimeter and in to spark plug wells 2, 3 and 4. I thought that the oil around the plugs could be causing some misfires, but I still get these symptoms even after I clean the oil out. I performed a leak down test with a Lang CLT-2. It showed 12% on 1, 3 and 4 and 15% on 2, which I think is not so bad (based on what I read). Mostly I only heard air from the dipstick tube which means the leaking I do have is from the piston rings and not the valves. However on #3, which still only had 12% leakage, the loudest sound seemed to be coming from somewhere down in the valve cover...almost as if I didn't have a good seal with the leak down tester and the spark plug hole. Of course it could have been coming out of an adjacent spark plug hole which is not good, but I couldn't be sure.

I have also cleaned the MAF, and removed the throttle body and cleaned the back off the butterfly.

I have plans to replace the valve cover gasket and while I am in there I may replace the fuel injectors, the fuel pulse damper (on the fuel rail), and the PVC and then also go with new plugs and wires (the plugs have 50k miles on them and the wires about 30k miles). I have considered replacing the coil pack as well. The one I have came from Autozone an I was thinking of replacing it with an NGK or Motorcraft one. I will also verify the engine/cam timing while I have the valve cover off, but unless a chain slipped, I don't think this is anything that would change over time. I verified that the crankshaft front pulley is timed properly (9th tooth at the crank position sensor when #1 is at TDC).

Is there anything else that I am missing? I know engines will lose power and be less efficient over time, but I have had cars with ~200k miles on them before and they have never ran this poorly and I noticed very little loss in fuel efficiency.

 

What YEAR is this Ranger

2.3l size was used from 1983 to 2011 but 2 different engines, 2.3l SOHC(1983-1997) and 2.3l DOHC(2001 and up)

Your profile says 1990 Ranger.......................but 60psi fuel pressure is 2001 and up pressure

If its a 2001-2003 2.3l then could be a problem with IMRC, 2004 and up didn't have that

If 1997 or earlier then could be FPR, and runs 30psi fuel pressure

 

It is a 2003 Duratec. Sorry about not posting that info. My profile is from an old 1990 I had many years ago, I need to change that.

Several years back (I am not sure how long, but it was between 2008 and 2011), I had a lean condition on #1. I had a difficult time finding it but ultimately traced it to the plug on the front (that holds the end of the IMRC rail) had fallen out. I purchased a new intake manifold and that fixed problem. I don't think the plug has fallen out again, so do you think it could be an issue with the part that controls the IMRC?

BTW, I did a compression check tonight and every cylinder was between 200 and 205 psi. So everything points to the rings and valves being ok.

 

I just did a search and found my old post where I fixed the problem. It was late 2011 when I replaced the intake manifold.

https://www.ranger-forums.com/dohc-2...-128852/page2/

 

I once saw a video of someone doing an IMRC delete and they were attempting to patch the holes where the metal rod passed. But I have seen others since that just pull out the metal rod and leave the holes between each runner unplugged. Then they installed the actuator which keeps the back end of the intake sealed and also makes the computer think the IMRC is still there and operating correctly. Are there any negatives to doing this? I know without the IMRC you can lose a little power down low and possibly gain an little at higher RPMs, but I was wondering more about leaving the holes where the metal rod runs between each runner.

I will have the intake manifold off while replacing the valve cover gasket, so I was thinking of deleting the flaps and metal rod, and then trying to clean the intake as much as possible then installing new gaskets. I know a dirty intake can make a car run poorly, so maybe that and dirty IMRC flaps are causing my issues.

 

Never did that myself, but Ford abandoned IMRC(intake manifold running control) in this engine in 2004-2011, only had it from 2001-2003

The idea behind it is sound, but implementing it is another story, an intake "runner" is the passage inside the intake that feeds an intake valve
When an engine is running the intake valve opens and air is pulled in, when the intake valve closes the air suddenly stops flowing and that creates a reverse pressure wave the goes backwards up the runner
When it reaches the end of the runner the pressure wave reflects back towards the intake valve
IF..........that pressure wave reaches the intake valve while its open again, then its like a mini-turbo, and forces more air/fuel into the cylinder, for more power

IMRC adjusts the "length" of the runner so "in theory" engine would have 2 RPM bands when they would get the mini-turbo effect

All intakes, even for carbs, are designed for this pressure wave effect, nothing new

 

Yeah, I assume it is a similar effect to how exhausts with expansion chambers work on 2 strokes. I don't think there are significant negatives to getting rid of it, but I just wonder about the holes between each runner. I don't think that would be significant enough to cause issues.

 

The intake is off and the and the IMRC seems to be in great condition. I plan on replacing the vac hoses that go from the solenoid to the actuator, and I will test the actuator with my mityvac to make sure it is working. Also, the intake and the flaps seem to be fairly clean. When I look in to the engine toward the intake valves, I see a moderated amount of carbon buildup, but when you look closer to the valves and the valve itself, it is perfectly clean I assume this is because the injectors spray in this area.

So I still haven't found anything that could be causing my issues. My O2 sensor has 146k miles so I am going to go ahead and replace that along with new plugs and wires. At this point I can't think of anything else to try.

 

Well O2 sensors over 125k will certainly cause false Lean that gets worse over time, by 150K they are done
Spark plugs should have a darker brown instead of light brown color
O2s generate their own electrical signal, they output 0.1 to 0.9 volts
0.1v is lean
0.9v is rich

so as chemicals run out the voltage starts to drop regardless of oxygen levels in exhaust, so a "false" lean and MPG slowly goes down, but it happens over many months even years so hardly noticeable unless you keep records on paper or in your head, lol
"why was I getting 24mpg last year but only 22mpg this year?"

Trust me, new O2s every 100k miles will pay for themselves over the next 100k miles, and gasoline ain't getting cheaper, lol

This is not about engine problems, its about engine efficiency, if an O2 fails out right it would cause running issues, this is about keeping money in YOUR pocket, where it belongs, lol

 

Yeah a friend mention replacing my O2 sensor and then later I read an older post by you regarding O2 sensors and that is why I ordered one last night. Mine used to get around 25mpg but now gets around 20-21mpg. However if I remember correctly from when I had the spark plugs out last week, they were a lighter brown. But I could be wrong.

 

I finally completed all of the work. New parts:

Motorcraft plugs and wires
Motorcraft fuel injectors
Motorcraft fuel pulse damper
Mazda valve cover gasket
Motorcraft PVC valve, o-ring and retainer ring
Mazda gasket for PVC separator plate and cleaned the inside
Bosch upstream O2 sensor
Verified the timing of crank, crank pulley, and cams was correct (with the timing kit)
Removed the IMRC rod and flaps and sealed the holes with 7/16 aluminum rod
Vac hoses for IMRC actuator and fuel pulse damper
Motorcraft gaskets for EGR tube, throttle plate, intake manifold and IAC.
Cleaned the inside of the intake manifold and the throttle plate

In the last few weeks I have cleaned the MAF, did a hot compression check (all within a few percent at around 205), did a hot leak down test (all 12-15%), and checked fuel pressure while running (65psi)

After I finished this, the valve cover leak seems to have been fixed, but the truck ran pretty much like before. But when I was putting the ignition coil back on, I noticed a very small crack on the side that faces the exhaust manifold. The original one failed around 2012-2013 and I purchased one with a lifetime warranty from Advance. It failed in 2016 (small crack) and was replaced and today I noticed the crack and took it in for another replacement. After replacing the coil it seems to run a bit better. When cold it still has a little hesitation, but it seems to be improved. Hopefully the fuel mileage will improve as well. I'm still not sure I have solved my problem, but outside of some sensor that is bad, but not bad enough for a DTC to be generated, I'm not sure what else to check.

 

Deleting the IMRC will change power band so that my be the hesitation you notice, the computer will still run fuel and spark timing like the IMRC is there and working

Glad its running a bit better, that's alot of work you did

 

After driving in one 3 trips yesterday, I'm not convinced it is running any better and maybe even a little worse. It definitely is still cutting out and hesitating at lower RPMs and it is much worse when cold. I'm going to drive around with my scan tool hooked up looking at the fuel trim numbers and hopefully get some ideas there. I still haven't driven it enough to need to fill up, so I don't know if the fuel mileage has improved. I guess it is possible for the MAF to have an issue, but I have no codes and I hate to replace such an expensive item when I don't even have a solid reason to believe it is bad. I have fuel pressure, new injectors, and new plugs, wires and ignition. So I think it must be some sensor giving bad or sporadically bad information to the computer. For example, I assume if the crank position sensor cut out from time to time, then the ECM wouldn't open the injectors or send a signal to the ignition.

 

Look at the CHT(cylinder head temp) sensor, that's the "ECT sensor" on the 2.3l Duratec, CHT tells computer how much "Choke" to use on warm up and when to not to "Choke" the engine
These were a common failure on the 2.3l Duratec, its between #3 and #4 spark plugs on the same center line of head/valve cover, need a LONG socket to swap it out

It should read outside temp at startup and then get warmer and warmer, of course, lol
And can be in C degrees instead of F

 

Thanks! I of course was all around that when doing this work, but I hadn't considered that one. I will be sure to check it when I'm using the scan tool.

 

I hooked up the scanner and drove to work today. The cylinder head temp sensor started at about 55F (ambient) and got up to a max of about 270F but on the highway was 255-265F. When I would drive at lower speeds it might get down to 245F. So that appears to be working.

Long term fuel trim stayed between 0 and -1. Short term was mostly 0-5 with occasional dips to -2 or -3. It was cutting out quite a bit and the registered misfires on the drive was 17. But I think it must miss some of the misfires because I would see the misfires increasing when it was cutting out, then later cut out just as bad and no misfires would be registered. After it is warmed up, it idles quite well. It still seems to misfire, but it is worse when cold.

The TPS seems ok too. With foot off the pedal it read 0.8V, with it all the way to the floor it was 4.6V and the transition between those two states was smooth and wasn't erratic.

The fact that the short term fuel trim looked good makes me think the MAF is ok and it appears the CHT sensor is ok as well. I have read you can measure the temp of the cat and it should be hotter at the rear by about 20F if it is working well. I'm not sure if that isn't a case if it indicates it is blocked or just that it isn't doing its job as far as emissions. I still have no codes.

 

Everything reads like it should

I assume the upstream O2 sensor was changed, didn't read back through the whole thread, lol
Older ones will cause unreported "false" lean, lowering MPG, O2s last 100-150k miles or 10-12 years max

Misfires come from cam sensor and timing of cam and crank rotation
When a cylinder fires it ADDS power to crank/cam so shaft speed stays the same(idle) or increases(accelerating), if shaft speed drops when it should stay the same or increase then its a "misfire" on the cylinder that was last to fire, these are the P030X misfire codes

There are also coil/spark misfires, there is feedback on the spark circuit from the coil pack to computer, these are P035X codes and will often come with the general P030X misfire codes if its a spark issue

What are your spark plugs gapped at?
There were some bad labels printed for these, on the rad support, and have extremely wide gaps recommended, i.e. 0.060+
0.044 to 0.051 is correct

 

Yes, I replaced the upstream O2 sensor with a new Bosch one. The downstream is the original one. I was going to get a Motorcraft one but it was going to take a few more days to arrive.

The scanner sees some misfires, but for some reason it only sees 17 on a 20 minute drive when it is obvious that it should be more than that. Also no code is being set. Is it possible that some sporadic misfires might be missed and not recognized as a misfire event?

I didn't know there was any feedback from the coil pack to the computer. How does that work? I only see 3 pins on the input to the coil. I have a new (aftermarket) coil and new Motorcraft spark plugs and spark plug wires. I couldn't find my spark plug tool for checking/adjusting the gap so I had to use my feeler gauges. 0.046 wouldn't fit, and 0.044 would on all four, so I figured they were right at 0.045.

On the way home I was looking at various things on the scanner again and I noticed that at full engine load and WOT going up a hill I would see some short term fuel trim figures get as far negative as -15. I know in conditions like that the values can be all over the place, but I thought 15 was about the limit of what is ok.

I have already performed a compression (205) and leak down test (12-15%), both with engine warm. I tried to get all of the oil out from around the plugs but it is possible some got down in the cylinder and made the results better. But with the leak down test I had a difficult time getting a good seal so I purchased one of these:

SKU : 73110 - M14 Compression Adapter Extension - Lang Tools

which makes it a bit easier to get maybe another 1/8 turn needed to seal it. I did a leak down test cold when the valve cover was off and #4 and #3 were a little on the high side, but from what I have read, a cold test isn't a very good one. But now that the valve cover gasket has been fixed, I will do it again to verify my original results.

 

I decided to perform a leakdown test and a compression test again. The reason is that I had performed a second leakdown test when it was cold and #3 and #4 was a little high. So I wanted to do another warm test because I thought when I had the leaking valve cover gasket, it is possible that some oil got in the cylinder when i pulled the plugs and helped the rings seal.

I got it warm and did the leak down test again.

#1 13%
#2 20%
#3 13%
#4 15%

So all are the same as the first warm leakdown except for #2 which is a bit worse than before, but I have heard anything better than 20% is ok. Also #2 was the last cylinder I tested and the engine had cooled a bit since by then, so maybe that made a difference. I found no evidence of leaking from the intake or exhaust valves or a cracked head. The only sound I heard was from the oil dipstick tube, so that means all of my leakage is from the rings. I then did another compression check. It was a bit lower than the previous test, but again the engine was cooler. All 4 were between 171 and 173psi, so that looks good.

Like I have said earlier, I have replaced O2 sensor, ignition coil, Motorcraft spark plugs (0.045 gap), Motorcraft spark plug wires, Motorcraft injectors, cleaned the intake among some other things. My fuel mileage had been 21 before (years past it was 24-25). On the first fill up it was 19.5 mpg. I'm still getting the cutting out below 2k RPMs and sometimes even a little above that. But it seems noticeably worse below 2k RPMs. And I still have no codes, but register ~15-20 misfires on a 20 minute drive to work. Sometimes when it is cutting out the misfires count does not increase, but every time the misfire count increases, it is cutting out/stumbling. I think I read it takes two misfires in a row on a cylinder to register as a misfire, if this is true then it makes me believe this is a sporadic problem that is likely happening on more than one cylinder. My code reader just shows "# of misfires", but doesn't indicate which cylinder is having the misfire. Is that normal? I would like to be able to see which cylinder is experiencing the misfire.

I also drove the truck to get it hot and checked the temp of the cat. It appears to be hotter at the tail end than it is at the head end, so that is an indication it isn't faulty. Also the MAF seems to give believable values on my code reader when I am driving as well. At this point I have no idea what else to try. I have all new components for the ignition, the valves and rings are sealing good enough, and I have verified the fuel pressure is good and now have new injectors. Since they are cheap I might try a new crank and cam position sensor and then I might go to pull-a-part and grab another MAF just to see if that has any affect. I have never randomly thrown parts at a problem, but at this point I am out of ideas. If that doesn't help then I am thinking I have some electrical issue somewhere (something not making good contact).

 

Today I went to pull-a-part and got a MAF and a coil pack. The one I have is new, but it is an aftermarket one from autozone...and I have been burned on aftermarket stuff not working well even when new. But while driving there I noticed several things:

The cutting out seems to almost suddenly stop or get significantly better EXACTLY at 2000 RPMs. It seems to have low power and I notice pinging at full throttle and as mentioned before I get worse mileage. Any ideas about what changes exactly at 2000 RPMs? I found this older thread and the guy seems to have very similar issues to me, but unfortunately he either never found the issue or if he did, he never reported back.

https://www.ranger-forums.com/dohc-2...m-help-145644/

 

No, nothing significant happens at 2,000rpm, there really isn't any RPM that would be different than any other unless you at the extreme ends, low rpms and high(valve floating) rpms

Pinging means engine is actually running LEAN, so should have better MPG, well until pistons melt, so lighten up on the gas pedal when you hear pinging
If engine was fully warmed up pinging can also be cause by carbon build up in the cylinders, this creates hot spots that pre-ignite air/fuel mix when its compressed
Pinging does reduce power since its not a complete ignition so less power is added to crank, so joking about the better MPG, lol

 

Engine is fully warmed up and the pinging isn't bad, but I notice it when I have it to the floor. My 1995 5.0L Mustang would ping on regular gas after it had about 75k miles on it. It would get better when running premium.

One thing that may or may not be odd is that my original coil pack failed back in around 2013-2014. I think it was a complete failure of one of the coils so it was a bad miss. I was near autozone and purchased one there. It lasted about 2-3 years and I started having missing again and noticed a crack on the side of the coil pack. I replaced it with the lifetime warranty and it ran better. Then recently when doing all of this work I noticed that replacement coil pack also had a crack in it. Is it just a poor quality coil pack or is there something causing these to crack like this? This last time (and maybe the time before), the crack was on the side that faces the exhaust manifold side of the engine. So I am wondering if the heat could be causing them to crack.

 

Yes, heat causes coils to crank but its internal heat, I would say poor quality manufacturing
Maybe pick a used motorcraft coil pack up at wrecking yard

Oh and I take that back about the 2,000rpm mark
I forgot this is a 2003 2.3l duratec so has IMRC which is an RPM and load based system, so does change positions, and could be your problem
I don't have an specs on the IMRC

 

Thanks. I did pick up a coil pack from a wrecked Focus yesterday. I verified that they are the same part.

As far as IMRC, yes mine does have that. Mine was in good shape when I had the intake off a few days ago, but I deleted the IMRC. I removed the rod and the flaps and sealed up the hole between each runner with a 7/16 piece of aluminum rod. I left the actuator on so that I wouldn't get a code. I would think that removing the IMRC caused this, but it was doing this before, but maybe is a little worse now. At this point maybe I should take the intake back off and put the IMRC back on and see if it helps anything. It really isn't THAT bad of a job. For me taking the wheel well liner out and putting it back is the worst part.

I unplugged the IAC at idle and it died, so I assume it is working properly.

 

I replaced the coil today with one I pulled from a Ford Focus. It ran pretty much the same . However I decided to test the spark. I have one of those testers that you can adjust the gap to see how much voltage you are getting. Something similar to this:

https://www.autozone.com/test-scan-a...ster/10257_0_0

I have no idea what type of ignition is in this truck, but for "standard" the instructions said 20kV and for a couple of different Ford types they had 28-30k and 30-32k. I first tried it on #1 and it was getting a good spark at 30kV but sounded like it might be missing here and there. Hard to tell. I adjusted it down to 20k and it sounded more steady. I did the same on #2 and #4. But when I went to #4 I started with it around 20kV. I started the engine and the spark was going for a few seconds then it was missing several sparks then it just stopped. I took the tester out and plugged the wire back up and was getting codes of a miss on #3. I measured the coil resistance and the input and output resistance looked fine (0.8 ohms on the inputs and 12.5kohms on the outputs). I put the other coil back on and it is running like it did before and the miss on #3 is gone.

What spark voltage should I see on this ignition? Is 20kV and starting to struggle at 30kV or a little more ok?

I know the energy from the spark has to go somewhere, but I assume the coils or the protection devices are designed to handle a spark plug wire coming off while running So I wouldn't think these testers could damage anything, so why did my coil seem to fail while using it?