[Terry S]

1992 Sable 3.0 120,000 miles. No codes but the engine would surge at idle in park or in gear about 500-1,500 rpm. Not always but most of the time. It also would surge some times when driving.

I cleaned the idle air control valve (IAC)but it did not help. Then I put a new IAC on and thought it was fixed. But after a few days it started surging again. The surging is not as bad but it is still there.

I am thinking the DPFE (delta pressure feedback of EGR sensor) or EGR Feedback Sensor may be bad. Is there a way to test it before replacing it?

Any suggestions or diagnostic help will be appreciated.

 

[eric m]

I have the same problem.

05 sable 99k miles, duratec engine.

My EGR system is in good shape.

Any help on how to trouble shoot would be appreciated.

 

[Terry S]

Anyone???

 

[Jeff K]

92 doesnt have DPFE, it has PFE. In either case, I doubt that is the problem. My guess would be a vacuum leak.

 

[pawpaw]

Good idea to suspect that pesky IAC.

I like the vacuum leak idea.

Maybe add the PCV valve & it's fittings & the vapor recovery vacuum line that connects to the intake manafold on the drivers side, to the suspect list.

A couple of years ago I found my vapor recovery vacuum line badly dryrotted & cracked, down under the battery tray, where it connects to a "T" fitting. The hose at the inake manafold fitting was showing some signs of cracks & was not fitting as tight as it should.
I had times when I would have an intermittent unsteady idle & sometimes could smell gas fumes in the cabin & sometimes would hear spark knock on a pull, but no CEL. Anyway, fixing that danged vapor recovery line solved those problems..

Maybe also add a dirty MAF sensor to the list, especially if you've modified the air intake, don't have the air box buttoned up properly, or are using an oiled foam, or cotton gauze type air filter.

If you decide to remove the MAF sensor for cleaning, use a non residal product formulated for cleaning the MAF sensor, like CRC MAF sensor spray cleaner. Let the sensor cool, don't touch it when cleaning & keep it squeeky clean upon installation.

More thoughts for pondering, let us know what you find.

 

[Terry S]

Thanks for all of the ideas. After doing an idle re-learn it is doing better. Hopefully that fixed it. The air filter and intake tube are stock and all look good there.

 

[ludacris]

Pull the vacuum line off the fuel pressure regulator while the car is running. Sometimes these will leak fuel into the vac line causing idle problems. It's an often overlooked problem.