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mwzephyr

Vulcan Engine Surging At Hot Idle

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I am curious~ My Vulcan just the last two warm days started at hot idle surging just a 100 rpms in range, but it has never done that before. Only in park. Does that suggest a small vacuum leak? As far as I can tell it is sealed tight. I just reset the computer / had the battery disconnected for about an hour/ when I was working on the ac problem ~ (which is still not resolved). Before that it used to idle smoothly with out surging. nothing the needle was like it was nailed in place on rpms... Any ideas? it is not missing... oil, is good, cooling is good, not overheating, ac is not on... replaced fuel pressure regulator sometime back. Air filter is good. Wires and plugs are new / only 6-7 months old. Starts easy and runs like a top... No panic attack here, but I like PURRRfection in my engines. plus I can not afford to ignore any warning problems and end up with a breakdown. maybe that silver thing bolted to the top back of the manifold that has two vacuum hoses routed to it from the egr tube? that is original... doesn't that affect the fuel/ air flow somehow? has a three wire connector going to it...What is its name?~Zep

Edited by mwzephyr

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I am curious~ My Vulcan just the last two warm days started at hot idle surging just a 100 rpms in range, but it has never done that before. Only in park. Does that suggest a small vacuum leak? As far as I can tell it is sealed tight. I just reset the computer / had the battery disconnected for about an hour/ when I was working on the ac problem ~ (which is still not resolved). Before that it used to idle smoothly with out surging. nothing the needle was like it was nailed in place on rpms... Any ideas? it is not missing... oil, is good, cooling is good, not overheating, ac is not on... replaced fuel pressure regulator sometime back. Air filter is good. Wires and plugs are new / only 6-7 months old. No panic attack here, but I like PURRRfection in my engines. plus I can not afford to ignore any warning problems and end up with a breakdown. maybe that silver thing bolted to the top back of the manifold that has two vacuum hoses routed to it from the egr tube? that is original... doesn't that affect the fuel/ air flow somehow? has a three wire connector going to it...What is its name?~Zep

I would start by turning the A/C off and see if that makes a difference. Just to eliminate that. When the system trys to engage the clutch, it jumps the idle up to correct for the load. If the load does not occur, then the idle will jump up. Low freon will make the A/C still work but at a reduced level. But the load on the engine is not mormal and the idle will jump when the system sends a signal to engage clutch.

Old school. check the easy ones first, eliminate the easy to check.

-chart-

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Hey chart, maybe I fixed something on the ac?... then I must be on the right track maybe just need to add Freon.../??? What you said makes perfect sense... I had replaced the 4-wire (spliced the new one in...) wiring connector on the larger ac switch and used the wiring diagram you gave me... maybe I had a bad connection to start with. Maybe just maybe I will get the ac fixed. WOW! perfect sense... thanks chart!~Zep

Edited by mwzephyr

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maybe that silver thing bolted to the top back of the manifold that has two vacuum hoses routed to it from the egr tube? that is original... doesn't that affect the fuel/ air flow somehow? has a three wire connector going to it...What is its name?~Zep

This thingy here?

IAC_vulcan.jpg

IAC (Idle Air Control) valve

$had3 :ford::merc::Shady_J:

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Sounds like the DPFE sensor.

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Sounds like the DPFE sensor.

oh... the OTHER thingy bolted to the intake, right next to that little round guy... Wonder if i need one, in that case...

$had3 :ford::merc::Shady_J:

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Sounds like the DPFE sensor.

Yep, DPFE has 2 hoses and elect connector.

Two kinds used. One just sits on top of the steel tubes, other is bolted to the head.

-chart-

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Its not the iac, but it is the DPFE bolted to the head. Now what does that stand for I wonder... I will have to look that up.~Zep

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EGR feedback sensor....= DPFE = Delta Pressure Feedback Egr Circuit is as follows top wire~DPFE flow signal middle~sensor ground Bottom~volt reference Differential Pressure Feedback EGR voltage - it's basically like a MAP or a barometric pressure sensor for your EGR system... Now I understand... ;) it senses pressure on either sides of a orifice in the EGR tube (why there are 2 hoses)the difference in pressure in the one closest to the EGR lets the PCM figure out how much the EGR is open. they use a piezo crystal sensor so any junk that gets inside them will cause an incorrect reading, anything causing the EGR to not open(broken vac lines or a blocked EGR passage)will cause a DPFE code as well. !B11cGyQ!Wk~$(KGrHqUOKiUE)(08r)VJBMgBpVCrQQ~~_12.JPG

Ford uses a Differential Pressure Feedback EGR (DPFE) sensor on these vehicles to measure EGR flow. Ford tests to see if the EGR valve is stuck open by checking the DPFE sensor at idle. The DPFE sensor tests for a differential in pressure across a restriction. As flow increases, DPFE voltage rises. Typical DPFE readings at idle are around 0.6 volts DC.

DPFE Sensor Failure

When the DPFE Sensor starts failing, it gives the PCM bad information. The DPFE Sensor is less sensitive, and the PCM thinks less recirculated gas is being burned than is actually so. Trying to compensate, the PCM opens up the actuator too much. This excessive amount of EGR combined with the air coming in via the throttle body leans out the fuel mixture, causing a lean misfire, which is the "stumble" or "hesitation" that is common as the DPFE Sensor fails. The DPFE sensor is not very robust, requiring frequent (every 30k miles or sometimes less) replacement or a work around. Note that complete DPFE sensor failure is a very slow process, and the check engine light won't come on until the DPFE sensor is pretty much done for.

If you're experiencing stumble or hesitation while cruising, could be the DPFE ~What I found on the net. ~Zep ;)

Edited by mwzephyr

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EGR feedback sensor....= DPFE = Delta Pressure Feedback Egr Circuit is as follows top wire~DPFE flow signal middle~sensor ground Bottom~volt reference Differential Pressure Feedback EGR voltage - it's basically like a MAP or a barometric pressure sensor for your EGR system... Now I understand... ;) it senses pressure on either sides of a orifice in the EGR tube (why there are 2 hoses)the difference in pressure in the one closest to the EGR lets the PCM figure out how much the EGR is open. they use a piezo crystal sensor so any junk that gets inside them will cause an incorrect reading, anything causing the EGR to not open(broken vac lines or a blocked EGR passage)will cause a DPFE code as well. !B11cGyQ!Wk~$(KGrHqUOKiUE)(08r)VJBMgBpVCrQQ~~_12.JPG

Ford uses a Differential Pressure Feedback EGR (DPFE) sensor on these vehicles to measure EGR flow. Ford tests to see if the EGR valve is stuck open by checking the DPFE sensor at idle. The DPFE sensor tests for a differential in pressure across a restriction. As flow increases, DPFE voltage rises. Typical DPFE readings at idle are around 0.6 volts DC.

DPFE Sensor Failure

When the DPFE Sensor starts failing, it gives the PCM bad information. The DPFE Sensor is less sensitive, and the PCM thinks less recirculated gas is being burned than is actually so. Trying to compensate, the PCM opens up the actuator too much. This excessive amount of EGR combined with the air coming in via the throttle body leans out the fuel mixture, causing a lean misfire, which is the "stumble" or "hesitation" that is common as the DPFE Sensor fails. The DPFE sensor is not very robust, requiring frequent (every 30k miles or sometimes less) replacement or a work around. Note that complete DPFE sensor failure is a very slow process, and the check engine light won't come on until the DPFE sensor is pretty much done for.

If you're experiencing stumble or hesitation while cruising, could be the DPFE ~What I found on the net. ~Zep ;)

I have had only 1 issue and it was a code for excess flow, maybe every 2 weeks to 2 months. No issue with performance.

DPFE_zpsa6c3ca02.jpg

So, my '01 has this version, no bolt, just sits atop tow steel tubes.

Got one from JY and no more issues.

Maybe 3 years ago or so.

That for '01 DOHC.

My '03 has the bolt on kind.

Your equipment may vary.

Depends on Ford's mood at the time.

-chart-

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My 05 with the U-vin Vulcan has the same fluctuations idling in park, I have a glasspack muffler in place of my stock muffler so I was thinking maybe it was a back pressure issue, but this honestly makes more sense because it fluctuated even before the pack was installed. It's at 103,000miles now, and it does this, when I stop, put it in park, it'll fluctuate up and down 100rpms for a while then even out, then some times do it again. It also has fluctuations while accelorating too some times.

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My 05 with the U-vin Vulcan has the same fluctuations idling in park, I have a glasspack muffler in place of my stock muffler so I was thinking maybe it was a back pressure issue, but this honestly makes more sense because it fluctuated even before the pack was installed. It's at 103,000miles now, and it does this, when I stop, put it in park, it'll fluctuate up and down 100rpms for a while then even out, then some times do it again. It also has fluctuations while accelorating too some times.

Idle speed is managed by the IAC.

I posted cleaning method here.

http://www.taurusowners.com/topic/3717-charts-tips/page__pid__47511#entry47436

See post #8

For me cleaning the IAC is maintenance, maybe every 2 years, or when the idle does not hold really close.

Low A/C freon can trick the performance. The system adds IAC speed to = the A/C load at nominal. If the freon is low, load is low and the car increases the rpm as it expects standard A/C load which is not there.

Pictures updated.

-chart-

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My 05 with the U-vin Vulcan has the same fluctuations idling in park, I have a glasspack muffler in place of my stock muffler so I was thinking maybe it was a back pressure issue, but this honestly makes more sense because it fluctuated even before the pack was installed. It's at 103,000miles now, and it does this, when I stop, put it in park, it'll fluctuate up and down 100rpms for a while then even out, then some times do it again. It also has fluctuations while accelorating too some times.

DPFE and IAC are good bets for malfunctions. PCV and IMRC are good bets for vac leaks. The IMRC on the '04 - '07 vulcans is known to leak. Check my thread: http://www.taurusowners.com/topic/2126-howto-fix-vacuum-leak-at-the-intake-manifold-runner-control-vulcan/. Test it first to see if it's leaking.

Also the glasspack muffler will not have enough of an effect on performance to cause the engine to surge. You will lose some bottom end power but the top end will be opened some.

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I "cleaned" the DPFE this morning with MAF cleaner by spraying it into the ports on the DPFE when it was disconnected and then let it drain for a few minutes~ after reading posts all over the net... It apparently has piezoelectric crystal (SP) or crystals in it... I don't know ~ but it is very sensitive to cleaners and to accumulated dirt coatings... MAF cleaner was said to be safe... I did not pull the battery/ reset the memory just restarted and after about 5 minutes the idle evened out. The car has been running much smoother. I notice these things, I am kind of picky about little stuff ~cause I know big stuff can follow.... Anyway I had a spare DPFE in case the one I sprayed self-destructed. Do this at your own risk... I used to clean IAC valves, but now I just replace them. My problem was a hot idle not a cold idle... Keep this info in mind from -chart - ~ "Low A/C freon can trick the performance. The system adds IAC speed to = the A/C load at nominal. If the freon is low, load is low and the car increases the rpm as it expects standard A/C load which is not there. " Before this I was starting to wonder if I needed to pull the butterfly for cleaning but I had just done that thoroughly 6 months ago when I installed new gaskets and redid the intake manifold thing... I appreciate the interest shown about this post! Thanks to all. Hope it will help others. :notworthy:All Hail the BULL MASTERS!!! ~Zep

Edited by mwzephyr

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I'm gonna have to do that today, I actually have a can of maf cleaner in my trunk with my tools.

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On 5/14/2013 at 6:36 PM, -chart- said:

I would start by turning the A/C off and see if that makes a difference. Just to eliminate that. When the system trys to engage the clutch, it jumps the idle up to correct for the load. If the load does not occur, then the idle will jump up. Low freon will make the A/C still work but at a reduced level. But the load on the engine is not mormal and the idle will jump when the system sends a signal to engage clutch.

Old school. check the easy ones first, eliminate the easy to check.

-chart-

just a question,my 07 taurus with the 3.0 has an erratic high rpm seems to be worse when its running at 2 to 3 thousand rpm and wont idle down right away.idle control valve and pvc valve has been changed,mechanic says no vacum leak any ideas?

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