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1997 developed intermittent miss

  • Thread starter Thread starter missinglinc
  • Start date Start date
So when it's cold, it runs perfect, seems if it was plugs or coil packs it would do it all the time regardless of operating temp... IF you got it down pat that this miss ONLY occurs after car is up to operating temp, that would steer me toward relays heating up and becoming faulty OR something along the line of open-closed circuit stuff, like what the O2 sensors go thru after reaching operating temp....I'd still be temped to swap that ccrm box, a heated up relay in there could play with electrical, and cause a miss..........
Now I know your intake manifold is different from my '95, but when it comes to swapping the ect sensor, were talking about the one with 2 or 3 wires coming out of it right ? not the single wire one that just works the gauge in the cluster right ?
Now you always say that it starts this missing after it comes to operating temp during a short drive, will it do this missing if it was not moving at all and just sitting in the driveway as it came up to normal operating temp ? That would be interesting, start her up cold and let it do nothing but idle till coolant temp shows normal temp, is it sitting there "missing" at idle and has never been moved yet ?

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Oh, one more thing, I've never seen a bad coil pack on these 4.6's, hardly ever a bad plug, but several times I've see some bad wires, from what I've seen, wires are good for about 60k on these 4.6's and that is good one's, I just put NGK wires on mine, and checked the 60k motorcraft wires that I took off and sure enough, 2 were out of range..........
 
The coolant temperature sensor is located beside the thermostat housing on my 97, according to the component locator that I looked it up on. The one for the gauge is located on the right side of the intake manifold. I took out the maf sensor and cleaned it again, took it for a road test, found it now had a hesitation, realized I had forgotten to plug it back in before I closed the hood. Stopped and plugged it in and hesitation was gone. I thought it was odd that it would run at all without the maf being connected.
I realized when I was working on it yesterday which bulkhead connector you were referring to previously and took it apart, cleaned and applied some dielectric grease. It was pretty clean but I took an air blowgun to both sides and also a good shot of sensor cleaner. I changed the coil pack on the passenger side, putting the one I had recently removed back on.
Test drive revealed no changes, so I also swapped the other coil pack, and cleaned up the tps connector and a couple of other ones.
Test drive, no appreciable difference, still has a slight misfire but it's at least drivable. New maf sensor is supposed to be delivered today so I will try that and see what if anything improves. I will pull the connector on the ccrm too and inspect it.
Haven't tried to let it idle until it reaches operating temperature yet, but I will if the maf replacement doesn't solve it.
As for a coil pack going bad, I had 2 of them go south on my 2002 Taurus 3.0 liter dohc engine, both times the engine developed a misfire once fully warmed up. The original one went at about 120k miles, and the new replacement lasted about 20k miles. Sold that car last year with 160k miles, still ran excellent but rust had taken a good hold of it, still have a new in box coil pack for it.
 
On that bulkhead connector, even if it did'nt change anything, we can mark that off in the future, it's been cleaned and new dielectric....
That is a little weird that driving with mass air un-plugged only gave a hesitation, I've never tried running mine un-plugged so I don't know, but I was always told that it would run but like crap, without that info going to pcm, the pcm kinda goes into a default setting, run just good enough to get it down the road if all you got was hesitation.....................
I also can't help but to wonder if were dealing with a faulty t.p.s., has it ever been changed ?
 
I do think I have changed the tps, but I could be confusing it with my 1990 Bronco, I know that I changed at least one of them.
New maf arrived yesterday, I put it in, engine wouldn't start unless I stepped on the accelerator slightly, but died immediately after I let off. Tried a second time, ssme thing, only cranked over until I depressed the accelerator and died as soon as I released it. Put the old one back in, started right up as normal, 1100-1200 rpm for a minute or two, then down to around 750-800 in park.
Let it idle until operating temperature before going for a road test, still have the occasional misfire, still no dtc codes.
Sent the second maf back today and requested a refund.
Starting to wonder if there might be a plug wire that's shorting out, did some reading on Ford Truck Enthusiast site regarding similar issues with 97/98 F150 4.6 trucks.
 
Couple questions, when you talk of swapping mass-air, are you swapping the whole unit or just the black sensor piece on top ?
When you first said you needed to push throttle a little for it to start, that sounds like idle air control issue, because that's how ya check IAC on a no-start condition, BUT maf changed that and you no longer need to press throttle a little, kinda makes me think this all may be something dealing with maf, like I said the only time I ever felt a miss while cruising was caused by the maf, that was about 15 years ago, it was my oem unit, not sure if it put out a code or not, too bad ya did'nt live closer, I've got spare working maf's sitting on my shelf, in fact over the years I think I've got a spare working part for everything under the hood, those parts come in handy when I sorting an issue out, that's why I'm not against trying some parts on things because in the long run you'll end up with plenty of working parts on the shelf, and as you probably know Ford service and motorcraft part are disappearing fast...........
In short, maybe for now center on that maf, IMO, I would not just swap black sensor, swap the whole thing AND while you there, make sure you get a good look at that maf pigtail........not sure what your trying in parts if ya can't get motorcraft but my money has been tight the last couple years and I've been trying some Walker parts, I've only been on these Walker parts for a couple years now, but so far so good..............
 
I did swap the whole unit, both times was Walker brand, which I noticed is made in China, whether that has any bearing or not I can't say, but I have read a lot about poor quality replacement parts of multiple brands made in China.
In years past I would typically stockpile several replacement parts for my vehicles, either from buying a complete parts car, or grabbing pieces from salvage yards when I found them. I still have several parts for the 2002 Taurus, some new in box yet, even though I sold it about a year ago. When I sold my 90 Bronco I gave the buyer about $1000.00 worth of extra parts that I had accumulated over the years of ownership. I'm finding the older I get, the less I want to collect parts, plus the financial costs are more challenging, especially considering that I have 4 vehicles and not much 'interchanges'.
I'll try another brand new maf, from hopefully a different company and see if it helps.
 
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