Hey fellers... '99 35th Ann. 4.6 vert, I am having the signature hesitating/stalling/stumbling-under-acceleration problem that this forum has many threads addressing possible causes and places to look. My question is: according to the Haynes Manual (NOT the definitive source, I know) the primary resistance reading on the coil pack should be around 0.5 ohms, and the secondary resistance reading should be around 5.5 Kohms... is this correct? All of mine read between 8.1 and 8.6 Kohms cold, using a FLuke 73 digital multimeter. All 8 packs are the originals. 144K on the odo.
Also, I have an intermittent charging light on my dash... no regularity to it at all, and the hesitation does not particularly coincide with the dash light. I replaced the battery, as it had a shorted cell in it and wouldn't hold a charge. I have cleaned the IAC, replaced the MAF, spark plugs, fuel filter, air filter, PCV valve. Any thoughts and help would be appreciated! I'll be out in the garage and under the hood, checking for vacuum leaks while you all ponder...
not sure on the coil packs, have you reset or tested your TPS (should read .98 volts)? and the charging light i assume would be something intermittent with the alternator.
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2000 GT VERT-- Far from stock, far from where I want it...
Heeeeelloooo out there??!! No one with any idea what the correct spec is for secondary resistances? The primary resistances all read 0.6 ohms... tenths of an ohm is as low as my Fluke meter will go. Also, I forgot to add that my car is a 5 spd, in case that matters. The hesitation only happens under load... can run and rev that car all day sitting in the garage in neutral... but as soon as I get it out on the street and drop that clutch... <<COUGH GASP SPUTTER>>
After reading the "Can you all stop and think" thread, the guy said COP's should read 8.3-9.2 Kohms when good, so I guess that rules those out as the problem in my car
And thank you Mr. PaperChasn for steering me more into the right direction... I made sure my new battery was well-charged, disconnected the alternator hot-wire and unplugged the monitor plug, went out and drove the car on battery juice only... no charging light on the dash and she ran like a scalded dog! It accelerated great, no hesitation at all, up until I got near redline... and then it just flattened-out sort of. The more I drove it and the weaker the battery got as a result, then it started to act up more... but as soon as I got back home, reconnected the alternator and took it back out on the road, the charging light came back on almost immediately and the hesitation and sputtering started on my first attempt to drop the hammer! So, I am taking the alternator out and having it tested... but I think that's the problem in my car.
Don't know how your alternator faired, but that surely does sound like the culprit. You may also want to try cleaning your Throttle Body with Carb Cleaner and a Tooth brush. Soot/dirt buildup on the butterfly plate of your throttle body can also cause hesitation.
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definitely the alternator or voltage regulator had a diode pack go bad in it. Of course Ford being the collective genii that they are have the voltage regulator in the alternator instead of external to it. So whenever either goes bad, they both get replaced.
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Well, I took the alternator to AutoZone and it passed their tests... but the test runs maybe 20 seconds... my charging light comes on after a couple of minutes typically. Also, when I spun the pully on the alt with it out of the engine, I could hear a weak chirp sound with every revolution... maybe the bearings in it are going bad, and it gets worse as it runs longer and the bearings heat-up? Your thoughts on that?
I also asked them to plug their scanner into the car and see if any codes come up... I have no CEL on, and they said with their little scanner, it wouldn't give any codes if the CEL wasn't on. That is very contrary to what I've been reading in this forum! Was the guy full of crap?
+1 with Bluestreak. However i thought our cars used a gen3 alternator because of it only having a single output terminal (B+). But in any event, check the connectors and wiring for corrosion and most likely i would have the alternator replaced just for good measure!
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2000 GT VERT-- Far from stock, far from where I want it...
HAve you checked your battery cables and ground straps?
My car was running poorly until we dug deep in there and found corrosion inside the insulation way up the cables.
The monster harnass/cable costs about $200.00 but the car runs great ever since we sorted the power situation out.
The charging system must provide steady, pure, power to the computer, senors and electronics or the whole car runs like crap.
Also the ground strap between the bottom of the engine and the firewall had rusted nearly all the way through.
Well, I finally pulled my head outta my butt and decided to check the DPFE... according to the Haynes manual, the signal line when backprobed should read less than 1vDC when the engine is cold, and it should read 4 - 5vDC when the engine is warm, and the reference signal line should read 5vDC always. The reference voltage is good, but when the engine is cold the signal line reads 1.03vDC and when at operating temp it reads 1.13vDC... whatcha think? Bad DPFE? I've always heard they were a high failure rate part... I know I've replaced it twice in two years in my 2000 Expedition which has the 4.6L in it also. But I've also heard that when the DPFE is suspect, the EGR Vacuum Solenoid could also be the culprit. I did the checks the Haynes manual says to do and they check out OK. So I guess I'll go with the DPFE. Any thoughts?
Changed out the DPFE... NO CHANGE! (Other than the voltages for the DPFE signal are correct now.) Replaced all battery cables... NO CHANGE. So, at the recommendation of my brother (a mechanic) I checked the voltage coming from the alternator. After first starting the car, it read about 14.1 vDC... kinda low to start with. I let the car idle a few minutes, and when I saw the battery light come on, I checked again... it was reading 13.8 vDC! And the longer the car ran, the lower the output went, with the battery light illuminated on the instrument panel the whole time... after idling for 20 minutes, the output voltage read 12.8 vDC. Sounds like a bad alternator!
Hey fellers... '99 35th Ann. 4.6 vert, I am having the signature hesitating/stalling/stumbling-under-acceleration problem…… ……... All 8 packs are the originals. 144K on the odo………
Hi Dango,
I had a pretty similar problem with my 2000 GT. At 115K miles I got misfires.
I checked the primary resistance, they were all between 8.3 and 8.8 K ohms - nothing suspicious. I couldn’t solve the problem until I swapped all COP’s for good used ones (17K miles)
So here is what happens:
1st: At medium RPM and acceleration (not WOT) a FI engine runs pretty lean. 2nd: Lean A/F mixture requires more spark energy to be ignited 3rd: Reddish spark I had on two coils means (low) energy (or bad condenser)
All this meant that the spark just couldn’t ignite the mixture.
So, when I swapped for new COP’s, I saw that two of the old ones had a micro crack in the epoxy. Moisture got into the coil and the electric charge arced over to ground or the primary side. That’s why the resistance was fine when I checked them with the multi meter, but the coils were still bad.
If your PCM doesn’t throw a code: The only way to find out is if you swap the whole set with a known good one.
If your PCM throws a code: Replace the COP on the misfiring cylinder with a brand-new one, and check codes again.
Since the insulation of the coils age with the number of heat cycles, and you say that you have 144K miles on the odo - I have my money on the COP's. See if you can borrow a known good set!
Next update... the voltages I read on the top post of the alternator were with the cable still connected to the post. I disconnected the cable and read the alternator output only, and it was fluctuating between 21.5 and 23.2 vDC! What the... ??? I'm thinking bad voltage regulator (which of course means alternator replacement since the regulator itself isn't replaceable alone)... the diodes in the rectifier circuit are breaking down with heat and not rectifying the voltage to 14-15vDC like they are supposed to do. If I had an o-scope to actually see the voltage jumping around and see if there is any AC ripple on the output, I'd feel more confident in that diagnosis. A digital Fluke meter just doesn't update fast enough to see how bad it is and doesn't read AC ripple reliably. Any thoughts?
OK, I read somewhere that the regulated voltage of the alternator should be 13.8vDC, with little to no fluctuation... so the 21-23vDC mine is spitting out is very bad. Anyone?
Coil Pack resistances 
