2001 Ford Taurus Duratec Surging Idle Problem

Hello, Guys, looking for some ideas on possible cause of a surging idle on my wife's Taurus. Noticed a slight surge on cold idle some weeks ago which went away once car warmed up. It has progressed to a pretty bad idle surge where it will stall out if car is in gear whether warm or cold. Some low-tech checks seemed to point to IAC, so I swapped it with a known good one (I have two of these cars) and hat made no difference. I used SD's spray-bottle approach for searching for vacuum leaks, but found none, but then again a a DIYer I do not do a lot of this. Anyway, I am kind of out of ideas. I pulled the codes with my simple scanner, and those codes are in pics below. Any suggestions? Thx, Pop

Does your scanner show live data? If so look at the fuel trim at different rpm and loads

The freeze frame data seems to refer to idle/low load condition. If the car runs worse/equally bad at higher rpm you may have a fuel delivery issue.

If the problem occurs at idle only you may want to look harder for unmetered air than you already did.

Otherwise you may deal with a dirty or contaminated MAF sensor. Many Ford's of that era allow to disconnect that sensor and will run much better in open loop then.

Thank you! I th8ink my scanner does do live data, so I will check and report back. I did try unplugging the MAF sensor and engine immediately died.

A buddy of mine used to work on a lot of Fords and I think he told me you have to unplug the MAF something like 3 times in a row before it will run in open loop.

Hey pop! Juergen is right on with his suggestion to check fuel trims in Closed loop at different engine speeds.

Most of the Tarui in my area are the Vulcan engine. Don't see a ton of the Duratec any more. But I do remember PCV hose leaks were very common (like every other Ford of that generation :silly:). May or may not show up during a spray bottle test.

Thank you gentlemen! I did unplug the MAF Sensor again and the engine rAn the same, surging and wanting to stall. I then pulled some live data with my crude scanner (Innova 5210) pictures below are the fuel trims at various RPM levels with car in Park. When I did these, at around 4000 RPM the engine started to miss badly, despite running smoothly at RPM’s below that but above 1000. It was also odd because on the road when passing, etc. I could wind it out and engine did not miss. I am pretty much lost here, so definitely looking for some guidance! Thx Pop

Attachments?

In park fuel cut may kick in causing the Miss at 4k rpm...

Attachments added to my previous post. Sorry for the accidental omission! - Pop

Got the attachments. Definitely keep pursuing a vacuum leak or unmetered air.

The misfire at 4K in Park is probably an intentional rev limiter like Juergen said. I wouldn't sweat it for now.

Thank you! Will check more for unmetered air.

Well guys, I think we might be getting somewhere. I got some starter fluid spray and sprayed around the intake and the engine reliably revved up and stayed revved as long as I sprayed the areas I highlighted in in yellow in the pic below. From right to left, these specific areas are: 1) inlet from pcv hose to snorkel 2) base/gasket area of egr valve 3) base of right two intake runners 4) vacuum hoses where they plug into the knob-looking thing on the passenger side of the intake.

I will proceed to: 1) replace the egr gasket 2) replace the intake gaskets 3) replace the pcv to be assembly 4) replace the rubber interface between the colored vacuum lines and the knob thing.

Any additional suspects you guys can think of? Thx, Pop

Pulled the intake, fixed the vacuum leaks plus a couple additional ones I didn’t see before, and now car is running great. Thanks guys! You are the best! - Pop

popoften wrote:

Pulled the intake, fixed the vacuum leaks plus a couple additional ones I didn’t see before, and now car is running great. Thanks guys! You are the best! - Pop

Glad you got it

The accessory belt doesn't look too good in the picture you posted, your better half may want you to have it checked

Thank you! If the belt does not look good to you, say no more, I’ll change it out!

Great to hear, Pop.

Postscript: A bit of surging has returned intermittently when engine is very cold (i.e., after sitting overnight in ~20 degree weather). Spraying starter fluid right into two of the injector holes consistently suppresses the idle a bit. No change to idle when spraying the fluid at other potential vacuum leak sites. Injector gaskets, perhaps? Thx, Pop

Yes, probably injector O-rings. They may "shrink" when cold and later expand when warming up.

Thank you!