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2005 Ford Taurus SE Sedan 3.0L
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Discussion Starter #1
Was digging around the forum for info, so figured I'd just ask, glad I came across this forum, definitely been a big help so far, inherited this bull and wanna keep it going as long as I can.

It's been happening for awhile now, changed out the IAC (I may end up having to re-do that, I went with a WVE by NTK brand IAC over MC, but doesn't seem to have made it worse or better, so it's probably just fine, haven't heard anything bad about the brand) and cleaned things as it was pretty covered in buildup, probably going to change out the MAF, TPS and PCV as well (Motocraft OEM parts), already have the new parts I picked up cheap, and the car has 119k miles on it.

Seems to be in the 6-800 range where it's kinda jumping around, doesn't really seem to feel hesitant or anything like that hitting the gas, maybe very slightly if at all, and the only time it's ever thrown codes are when it's colder weather, it'll throw the P0171 and 174 lean codes, but the codes never show up any other time, as a matter of fact the last time I saw any codes was back in December, nothing since, it went off on it's own.

I'm going to replace the plugs and wires, since I'm almost positive they are original, I haven't come across any vacuum leaks and any loose hoses I've snugged up that I could find.

I have noticed when turning the A/C off I do feel an idle drop and then it's back to the juggling between 6-800, does tend to feel slightly rough and drops below that, but higher rpms don't see to have issues, just idle, so far the rpm needed is just jumping up and down in that range, but not codes or stored codes as of now with the issue.

I've seen a lot of suggestions on it, just curious for more input before I start digging too deep possibly the wrong way with it, as it's pretty annoying.
 

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Fwiw, Motorcraft iac is the only brand that seems to work well on the bulls. If too expensive new, may get 1 from a pick-n-pull jy and clean/lube/install. The intake runner/tuning valve gasket at the pass. firewall is a notorious vac. leak. It's about the size of an oil filter gasket.
 

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2005 Ford Taurus SE Sedan 3.0L
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Discussion Starter #3
Thanks for the suggestion, I'll have to check that area out more carefully when I have more time next weekend, gotta be on that side to replace the washer jets and the hose that disintegrated anyways, just had to replace the coolant reservoir because it was cracked at the top, and the water hose return from the top of the tank to the top of the radiator today because my dumb self routed it wrong without thinking and the pulley ate it, but, I guess it gave me a reason to do full flush out and get it back to what the factory manual recommends for coolant, lol.

Thanks again, I'll definitely check into that side to see if there is a vac leak there that I might have missed, and I'll see about picking up a Motorcraft IAC instead, because the NTK I got seemed to have been knocked around in shipping anyways, so could be bad from that, or just the bull doesn't like it if it's not a leak.
 

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2005 Ford Taurus SE Sedan 3.0L
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Discussion Starter #4
Fwiw, Motorcraft iac is the only brand that seems to work well on the bulls. If too expensive new, may get 1 from a pick-n-pull jy and clean/lube/install. The intake runner/tuning valve gasket at the pass. firewall is a notorious vac. leak. It's about the size of an oil filter gasket.
Also wanted to say thanks again for the heads up, was able to get a return for the IAC part that I bought, managed to source a new Motorcraft IAC for a good deal, so gonna get that installed when it arrives, usually I'd clean the old one, but I'll just hang onto it and install a new one, does have 119k miles of use on it, so probably doesn't hurt to replace it.
 

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I just went through this on my 05 Sable with the vulcan. The coil pack was cracked. Unbolt it and check the bottom for cracks. I did put plugs in just because they were in there for many years but they didn't look bad. On the scan tool there weren't any codes but mode 6 data showed random misfires on all cylinders, not enough to trip a code. It was behaving just like yours.
 

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2005 Ford Taurus SE Sedan 3.0L
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Discussion Starter #6
I just went through this on my 05 Sable with the vulcan. The coil pack was cracked. Unbolt it and check the bottom for cracks. I did put plugs in just because they were in there for many years but they didn't look bad. On the scan tool there weren't any codes but mode 6 data showed random misfires on all cylinders, not enough to trip a code. It was behaving just like yours.
Thanks for the heads up on that one, I completely didn't even think to pull that off to check honestly, and if the symptoms on yours were the same, then It's a good possibility that it might be cracked on mine as well, lot of heat cycles and mileage, so It's possibly.

It's pretty sporadic with the crazy rough idle, and only sometimes does it get really rough, either randomly or after the A/C is turned off, but not all the time, and it jumps around in the 6-800 range normally, and only throws codes in winter, which if it's cracked going from being cold to hot would mess with it more probably, only ever thrown a misfire code once, but only when it was pretty cold, then went away when the weather warmed back up, not that it gets super cold in Florida, but still, ha-ha.

Definitely going to pull it off this weekend and take a look at it and see if there are any cracks though. Thanks again though!
 

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Use a scan tool that shows PIDs and look at LTFTs (Long Term Fuel Trims) on both banks at idle and driving at 40-50 mph. High positive values that drop with engine under load = vacuum leak. It doesnt take much of a vac leak on modern engines to cause idle and performance issues. 99% of the time vac leaks are too small to hear them.
 
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Discussion Starter #8 (Edited)
Use a scan tool that shows PIDs and look at LTFTs (Long Term Fuel Trims) on both banks at idle and driving at 40-50 mph. High positive values that drop with engine under load = vacuum leak. It doesnt take much of a vac leak on modern engines to cause idle and performance issues. 99% of the time vac leaks are too small to hear them.
That is another great idea, I just bought a new scan tool that let's me check ABS codes/bleed ABS and all that stuff for when I have to change the master cylinder, since I'm certain it has a small leak in it, and I can view PIDS, so I will definitely do that and check out the LTFTs and see what the numbers are for those conditions and see if the values are in that range.

While I was thinking about it, I did have another question, I bet I'm not the only one with the issue, that vacuum line that attaches under the windshield drainage skirting towards the firewall, one end is hanging down and the other end is still clipped securely going towards the drivers side, rather than it hanging down and touching the UIM, is there a particular way you can recommend to secure it back up?
 

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2005 Ford Taurus SE Sedan 3.0L
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Discussion Starter #9
I was checking hoses and stuff today after work, haven't had a chance to drive with the scan tool plugged in to check the LTFTs, but I did notice something when looking at the upper intake manifold towards the rear, the Intake Manifold Runner Control Valve (IMRCV) I guess is the correct term for it... it doesn't have any electrical connector plugged into it, and I'm assuming that obviously all bulls would have something plugged into it?

Possibly that could have something to do with the idle issue? It's not super crazy, except for sometimes and in the winter it does the codes like I said, but I was browsing the forums about changing the gasket on it and was looking at it and noticed there was absolutely no connector on it.

If there needs to be one, can anyone maybe post some pictures of where the connector would be coming from? I'm not sure what the correct name for it is, and I don't remember seeing it in the service manual DVD that I have, unless I overlooked it.

Thanks for all the help so far, greatly appreciate the wealth of knowledge on this board!
 
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