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Discussion Starter · #1 · (Edited)
I've got a 2000 Taurus with the Vulcan engine and sporadically when at cruising speeds and RPM's I get a slight RPM surge. It will rise or drop around 100 RPMs several times. The Tach. needle looks like it has a slight bob to it. It doesn't seem to be a major drivability issue, but I would like to fix it. Is it just a vacuum issue and if so where should I start to look? I did notice that it mostly happens if the fan is turned on a non-air condition position. It does not seem to have the surge if the fan is turned off. If not any suggestions would be appreciated. It does not seem to do it at moderate speeds or during idle.
 

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You get some tach movement @ a stoplight too , don't you?
Vulcan engine (lower power engine)
 

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Discussion Starter · #3 ·
I might occasionally get some tach movement at stoplights too, but it is not noticable. It is noticable when at cruising speeds. The needle seems to bounce a little. With it affected by turning the fan on is there something in the climate control system that is leaking vacuum? Or is that just an additional stressor that increases how noticable it is?
 

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What speed are you going when this "Surge" takes place ?
 

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Whoa, I was just doing a search to see if anyone had posted a topic like this 'cause it's happening to my car.

I have a '99 with a Vulcan, and I'm getting an intermittent surge at highway speeds. For me, it starts very subtly around 55 mph and will slightly increase as my speed increases. Nobody riding in my car has noticed at those speeds (I think), but it's noticeable to me. Along with that, my tach needle will bob 100 to 300 RPM.

On an interesting note, two days ago I had the car cruising in 1st gear for maybe 15 seconds around 3,000 RPM or so and it became VERY noticeable. The car was surging hardcore and felt like a kid driving stick for the first time.

Anyone got ideas?

EDIT: In response to thesavo, my trusty steed has ~119,000 miles, 32,000 of which were put on by me over the past three years. The surging only became noticeable about a month ago after a day I pushed it far harder than I should've (late for class - turned an hour drive into 45 minutes), and I can feel it getting worse, so I'm inclined to think it's more than just the design of the engine...
 

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heh, my tach bounces up and down 100 rpm when I have my AC on low while idling.

It doesn't do it while driving either. With the AC on high it doesn't do it. Only on low.

I've given up trying to figure it out honestly. Nobody can figure it out lol

Edit - and I'm not talking about when the compressor kicks on it moves. I mean the needle bounces like Vroom, Vroom, Vroom, Vroom
 

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heh, my tach bounces up and down 100 rpm when I have my AC on low while idling.

It doesn't do it while driving either. With the AC on high it doesn't do it. Only on low.

I've given up trying to figure it out honestly. Nobody can figure it out lol

Edit - and I'm not talking about when the compressor kicks on it moves. I mean the needle bounces like Vroom, Vroom, Vroom, Vroom

You have a dirty IAC valve, it's a common issue. If the idle is going down 100 rpm and then it goes right back up (Within 1 second) it's NORMAL. If it stays down while the A/C Clutch is engaged then its a dirty IAC.
 

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I have a '99 with a Vulcan, and I'm getting an intermittent surge at highway speeds. For me, it starts very subtly around 55 mph and will slightly increase as my speed increases. Nobody riding in my car has noticed at those speeds (I think), but it's noticeable to me. Along with that, my tach needle will bob 100 to 300 RPM.

It sounds like you have a faulty DPFE thats causing your surge, the DPFE or Delta Pressure Feed back Sensor pulses the air from the EGR and is a flow sensor. If these fail (They do VERY OFTEN) every 15-30K these need to be inspected and replaced if you experience a surge while cruising above 40 mph.

In your case I think that the DPFE causes the surge and causes your transmission to come out of torque converter lock-up causing the 2-300 RPM surge while you are driving.

That being said I think that's what is happening with the O.P.'s vehicle but they have not responded to my question. B)
 

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Here is what the IAC looks like (You have all seen this if you have opened your hood)



On the backside it has 2 ports that look like this....



There is a rod that moves between those 2 ports that actuates the Idle, I would use Throttle Body cleaner in BOTH ports and do this a few times untill the cleaner comes out clear. It will come out BLACK if you have never cleaned it before, after that's done then you can air dry it or blow it out with compressed air.

Keep in mind that you may have to get a new gasket for the IAC if it breaks apart (Mine didn't with 137K) Reinstall it and you should notice an immediate difference in the idle quality of your Bull. If not you just may have a faulty IAC (Pretty Rare though.)

Troy.
 

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It sounds like you have a faulty DPFE thats causing your surge, the DPFE or Delta Pressure Feed back Sensor pulses the air from the EGR and is a flow sensor. If these fail (They do VERY OFTEN) every 15-30K these need to be inspected and replaced if you experience a surge while cruising above 40 mph.

In your case I think that the DPFE causes the surge and causes your transmission to come out of torque converter lock-up causing the 2-300 RPM surge while you are driving.

That being said I think that's what is happening with the O.P.'s vehicle but they have not responded to my question.
Thanks! B) Makes a lot of sense, and some research on other sites pretty much describes what my car is doing.

There shouldn't be anything too specific about a DPFE right? I found this on eBay:
STANDARD SMP DPFE EGR PRESSURE FEEDBACK SENSOR VP8 | eBay

Fits most Fords between 1997 and 2008, and the 1999 Taurus is listed specifically in the compatibility table. If I need to get more specific, where would I find a part number for the one in my vehicle?
 

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www.fordparts.com - Enter your vin and search, they will have the part number listed.
 

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I would suggest a DPFE for you as well, if it's not the DPFE your transmission is going in and out of torque converter lock-up and that ain't good if your foot is steady on the gas and it's happening.
 

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Bumped for update.

I changed the DPFE sensor on my car two weeks ago, drove it for couple days, and noticed that the A/C & RPM issue was still happening but no check engine light popped up. Three or four days later the SES light comes on so I read the code, but it's the "small leak in the EVAP system" one (think I need a new gas cap). I could still notice the A/C issue (and I desperately need that in this heat), so today I decided to push the car hard and see if another fault would light up.

So on my way to work I kept it between 75 and 80 mph on the interstate for a good 20 minutes and I pulled the codes before I went into the office. Sure enough, that good old P0401 - "Insufficient EGR Flow" is back, so the sensor didn't do the trick as I had suspected after changing it.

What would be the next things to check for this thing? I saw on an F-150 forum that cleaning out the throttle body could do the trick, but I haven't had any rough idling or stalling problems...
 

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You may want to check on the EGR's condition, they can get gummed up with carbon or the diaphram can get a hole in it causing the EGR to not actuate with vac.

The DPFE was replaced and this more often than not clears up a surge problem, but if you have an EGR that is failing it can also cause this issue. My ranger had a VERY gummed up EGR and I too had a small surge at cruising speeds as well as Idle issues, it cleared up after I cleaned it out.
 

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Rico, if you have a 99 duratec, you probably need to pull the throttle body and its gasket and clean out the c-channel and the passageway to the egr valve with spray cleaner, small screwdriver(s) and baling wire. Do this with the egr valve removed. Clean it also.
 

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^I have the Vulcan...

Well yesterday I cleaned out the throttle body and the EGR as well:



Afterwards I drove about 100 miles with no problems. I stopped to pick up some food, came back out, drove three miles and boom - SES light comes back on. I read the codes, and it's the same P0401... :angry:

At this point I say it's a faulty EGR valve, what do you guys think?
 
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