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Strange random misfires


Fleetspell

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Hi everyone. I'm new here. To start off, for whatever reason, I tried opening the "search this forum" button and it never would do anything. Like a dead link. Idk. I have an 03 2wd automatic ranger with the 2.3 and 173,000. Last week it started misfiring alot and cel came on and started flashing. When I got home I hooked it up to scanner. Sorry but can't remember those 2 codes now since I've erased them, but one was misfire on cylinder 3 and the other was misfire detected in first 1000 revolutions or something like that. It idles smooth and doesn't seem to miss. It only misses if I punch the gas hard or once it's put under load like in drive I can hold the brake down and hit the gas and it will start missing real bad but goes back to a smooth idle. So i did the obvious first which it needed. I changed the plugs and wires. I put in autolite double platinum and checked gap and installed motorcraft wires. There was no change. Then changed fuel filter. I checked fuel pressure at rail with 55psi. At this point I had nothing to do but check and clean. I visual inspected and checked every stinking linear inch of vacuum line on the thing, which the ones on the back and lower driver side are a pita. No vac leaks. I did compression test. 1-4, 180 175 178 180. I pulled fuel rail. Injector resistance was good. I bench tested and cleaned injectors to make sure the solenoid s we're in good order and to visually make sure I had a nice fine mist of carb cleaner coming out of them. Replaced orings on them and reinstalled. No change. I visually inspected coil and epoxy fill on bottom for cracks, no cracks. I checked primary and secondary resistance. Secondary was 1.1 on both. Primary was 33,000 I think. Those numbers might be backwards. I didnt write them down. I should have. I didn't because once I looked up the acceptable tolerance mine was within the range. So according to the numbers the coil was ok. I did a voltage test on tps. Nice and smooth and no change when tapping on it. I gave throttle body a super good cleaning. Reinstalled with new seal. Cleaned maf with crc maf cleaner. 3 years ago I blew out the front plug on the intake. You 2.3 guys know the stupid plug I'm talking about. Ireplaced it with a doorman intake. So I checked this and sprayed all over the intake with started fluid. It is in good shape. No leaks. I cleaned map. I checked the manifold runner diaphram on back of intake. It is working properly and the rod is hooked up. Replaced pcv valve. That's a shitty spot for that btw. Only thing I can think of is maybe the camshaft position sensor? Or the EGR valve. Can't even see the EGR valve back there, don't how I would even begin to take it off. Another shitty location. I checked and cleaned ALL engine compartment grounds for s and g. Took main engine harness apart. You know the one under intake on driver side that bolts together. I cleaned that with electronics cleaner and put dielectric grease back on all pins. The last test I did was hook an inductive timing light to each plug wire. I get a nice smooth light pulse on each wire. When I give it throttle quick. I get misses in flashes. On every wire. It's random. I don't know what else to check guys. Does the camshaft sensor provide the signal to the coil on this engine. I know dumb question. I have a new coil on the way. Got a good deal on it. I know u guys think I've wasted a lot of time on this. I have but I consider it way past time to do this stuff and Its a DD so it needs it. I'm sorry this sooo long but I wanted to be thorough and present as much info as I could so no one be guessing. Any thoughts would more than be greatly appreciated. Thanks guys.
 


Fleetspell

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Sorry. Forgot to mention I cleaned the iac valve as well. That's all.
 

RonD

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Welcome to TRS :)

Try breaking up your sentences into paragraphs, will make for easier reading

The Crank sensor sets base spark timing and injector timing
Cam sensor is used to fine tune fuel injection and to some extent spark advance and retard

Crank or cam sensors either work or they don't, no in between or intermittent issues

After engine is warmed up, and idling, unplug the IAC Valve's two wire connector
RPMs should drop to 500 or engine may even stall, either is GOOD, it means no air/vacuum leaks
If RPMs do not change then you have a leak

When you step on the "air" pedal, used to be called the gas pedal :), you are adding more air to the engine and rotating the Throttle Position Sensor(TPS), this sends a higher voltage to computer(PCM)
When PCM sees the higher voltage it increases the fuel injectors open time, adds more fuel quickly
When there were "gas" pedals the accelerator pump in the carburetor squirted in extra fuel when you press down on the pedal for quick acceleration, which is why it was called a gas pedal, it actually added more gas, lol.

If accelerator pump wasn't working well you would get a misfiring and hesitation because extra fuel wasn't being added when needed.
Maybe your TPS is not being as responsive as needed.
You can test it with a Volt Meter, use a sewing pin to pierce the wires when testing
Top wire should be 5volts, key on
Center wire should be under 1 volt, throttle closed, spec is .69-.99volt
As you open the throttle voltage should go up slow and steady, no jumping or dropping
At Wide Open Throttle(WOT) it should be above 4.5volts, 4.50-4.99volt is spec



Joking about the "air" pedal of course, it is true, with fuel injection it is an air pedal only, no gas involved any more.
 

Fleetspell

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Im about to leave for work. Im the plant engineer where I work and I always go in an hour early everyday. I'll check iac and the tps again once I get to work.
 

Fleetspell

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Ok. I unplugged the iac. It did drop to around 500 rpm. It was noticeable. I checked tps. I only got 0.04 volts on top wire. The bottom wire however measured. 5.05 volts. The center wire test was 0.84 volts on closed throttle and smoothly transitioned to 4.55 volts at work.
 

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"They" must have put TPS in upside down on the 2.3l Duratec, lol

But it all tests as no vacuum leaks and TPS is OK.

When engine is cold, just after starting, the computer does not use O2 sensors and ignores most other sensors, it also doesn't use the EGR system.
This is called Open Loop operation, computer uses pre-programmed air/fuel mix tables in fixed memory based on RPM and engine load(TPS)

Does the engine miss when it is cold?

Or do you only notice it after engine has warmed up, this is Closed Loop and computer is using all the sensors



Call a Ford Dealer with your VIN number in hand, see if there is an update for the computer software
I haven't read about this specific problem but maybe there was an issue that was fixed by an update
The 2.3l Duratec engine was mainly used in front wheel drive cars, so may have been issue there that "we" don't see much
 
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Fleetspell

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Seems to only do it once it's warmed up. But it doesn't have to run very long at all for it to start. Maybe 3 min or so. It does it definitely before it reaches normal operating temp. I'm going to have that coil in a few days. I'll post back with the results once I install it. Thanks for your help btw. I haven't told you yet. I appreciate your time.
 

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3 minutes is enough time to warm up the O2 sensors that's when computer starts to use them
Exhaust runs at least 700degF so doesn't take that long to warm up upstream O2, and they are heated as well

I wouldn't expect coils to act up until engine bay was warmed up
 

Fleetspell

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Ok so my coil came in today. I installed it and there's no change. Suspected so but I got a really good deal on it so not a big loss. Any other suggestions guys?
 

Fleetspell

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So I was just out there tinkering on it and saw some melted wires. Tried uploading a picture but it said I wouldn't​ because I would manually have to resize it. Don't know how to do that on my phone. Anyways the wires come out of the iac and some wires that just come up out of the valve cover between spark plugs 2 and 3. They go into a plastic holder above the exhaust manifold.

They have gotten hot. I guess I'll be tracking wiring now. Sucks cause I hate removing that factory plastic sheathing and cutting all the electrical tape off.

I'll start just by repairing what I've just found and go from there. Does this sound like it would cause the misfires? Either way I'll get this fixed.
 

Fleetspell

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Ok that other thing I was talking about is the cylinder head temp sensor. If this my prob why does my gauge read right and no other codes are thrown. This problem doesn't even seem to be part of the original issue but it's a good thing I found them.
 

Fleetspell

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Ok so here's an update. I cut the sheathing back lower to follow the cylinder head temp wires down into the plastic harness. Once I cut the tape off the top of the plastic harness I found several wires melted together.

The ones I'm not sure about are grey with a red stripe. There are 4 of these wires in the same bundle of wires. I'm pretty sure 1 runs to the top wire on the tps. One goes to maf. One goes to map. Basically once I started fiddling with them they fell apart. So I have no idea how to tie these back to their proper sensor.

So there are 4 of the gray wires with red stripe coming from back to engine and only 3 wires on the front side of the break. This is insane. I don't know why Ford would do this. Kind of defeats the purpose of color coding.

Anyone have any ideas? I attempted to connect these back up and it's obvious it's wrong because now it won't even fire up. I'm gonna start with a pcm pin out and try to figure out what goes where. Seems like this could be a common issue.
 

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The grey/red stripe wires are called Sig Return, signal return, pin 91 on the computer, basically they are the Ground for all the sensors that use the 5volt Reference Voltage that comes from pin 90, brown/white stripe wire, on computer.
Each sensor with a grey/red wire will also have a brown/white wire, ground and power

Sensors need a common voltage, reference, and common ground Return, or the sensors output voltage, signal, wouldn't be as accurate, it could drift up and down.

So all those Grey/red stripe wires are actually one wire, they all run back to pin 9, so are all connected together

I don't think thats your no start problem.

Only one sensor can cause a no start, the crank sensor, and it doesn't use computer voltage, it generates its own AC Voltage when crank is turning
 

Fleetspell

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I just wanted to update and wrap this up. You were right about the gray and red stripe wires all being together. I soldered them all together and shrink wrapped them. It runs great and no stored codes. However there is a little stumble on acceleration. Im not getting a spark miss now tho. So that problem is finally resolved.

Something told me to double check the imrc rod again. It was in fact hooked up. I removed the intake. Sure enough it was hooked up but the white piece of plastic that presses onto the steel square rod had rounded out some how. So the actuator was moving up and down but the flaps were not moving even tho everything was hooked up.

I'm just going to do the flap delete on it and be done with it. The intake is only a few years old and for this to already happen doesn't say much about the products quality.

Anyways, thank you Ron d for all of the knowledge you had to offer. I guess you're the only one on here that knows enough about the 2.3 duratec to offer solutions.
 

mikeA

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Hi, new member here. I wanted to offer a super super valuable data point somewhere, and this question looked like the best place. Keep this one in your back pocket - because it *is* valuable. I had the same problem - strange random misfires all over the place. Ranger 2001 4-cylinder.

Here's the scenario. I was having a minor electrical problem - the alternator light very occasionally. And like a total idiot, I stopped by Firestone to have them look at it, and also change a belt that was going bad. After I left, I was getting strange misfires all over the place. No way I was going back there. Like a further idiot, I took it to the dealer. I figured they knew the engine the best. They charged me a bundle, and returned it with nothing apparently done to it, and acted like it was running normal.

Out of shear luck, I knew somebody who worked as a mechanic on high end cars. He looked at it for an hour, and on a remote - it couldn't possibly be - hunch, the genius got it. The engine is dual spark plug style for cleaner burn. The FUKWAD at Firestone swapped 2 of the cables on the secondary distributor cap - which does the secondary burn for cleaner burn. And that was "just" enough to make the engine so mysterious hard to diagnose that I thought I had no choice but to trash it.

Keep that one in your back for the super mysterious misfires. And also, any legitimate variations of this could be anything else that affects the secondary fire.
 

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