rpm surge

[pontiacdude]

help!!new to this forum and fords just got a 95 explorer xlt nice truck but while driving down the road at a steady speed 40 or 50 the engine surges.at idle it doesnt it idles nice but holding the rpms at 2000 in park it surges 2000 -1500 or so.tps checks out good no check engine light pulled the 02 sensors visually they check out as burning right.havent found a vac leak but cant exclude that. any help guys? i know youve run into this please help it makes my wife car sick surging like it does.thanks
pontiacdude

 

[aldive]

Have you cleaned/replaced the IAC?

 

[pontiacdude]

no i havent. its not an idle problem but off idle could iac still be the problem ?ill look into that thanks alot.

 

[///Manuel]

I might have the same issue, http://www.explorerforum.com/forums/showthread.php?t=172468. I changed the IAC and it didn't make a difference. Some sensor is screwed up in there but I can't think of which one.

 

[Turdle]

Try disconnecting the maf sensor--it will illuminate the CEL, however, does it run better???

 

[pontiacdude]

i unplugged maf sensor ran bad out of the whole but i think surging was gone going down the road but surged worse holding it at 2000 rpm in park .plugged it back in ran good but surging was back not to bad holding 2000 rpm in park but going down the road it is there

 

[tinksmartbstupid]

Having idle/drivability problem, I pull the MAF and it idles better. but I just replaced that, the MAF connector, and the Idle air speed motor. I've got 1994 ford explorer eddie edition. any ideas?

 

[pontiacdude]

well i changed plugs then wires then sprayed carb cleaner around the intake gasket no gasket leak still have my surge had to give my wife my 01 suburban and take her piece of crap explorer.

 

[jamester_a]

Surges while cold? or warm only?

Does your truck do its surging thing before it is warmed up? If not, it may still be your O2 sensors as they don't come into play before the ECU is in closed loop - i.e. engine at full opertating temp. Other than the MAF, have you tried to run with 02s disconnected?

- James

 

[pontiacdude]

The Surging Is The Same Cold Or Warm .im Tired Of Tracing This Problem Gonna Take A Few Day Break.then I Might Try Unpluging The 02's.wont That Really Throw The Computer Off?

 

[pj8847]

If the MAF, TPS and IAC check out fine, and you have no apparent vacuum leaks, and a clean air filter, next step in the diagnosis would be fuel delivery.

Possible clogged fuel filter, malfunctioning FPR, maybe low fuel pressure from failing pump...

First make sure the fuel filter is good, then get a pressure gauge and pop it on the fuel rail and grab a reading. If i remember correctly (someone please correct me if my memory has failed me) an acceptable pressure reading should be within the range of 30 to 45 PSI on the rail. If it's low, then you have to figure out if it's the FPR, or the pump (usually the pump)

Don't bother unplugging the O2 sensors. It has the surge whether its just started, or been warmed up you said, so O2's obviously not the problem.

 

[NHale623]

A fault DPFE sensor, ECT or IAT sensor can also contribute to this problem.

Have you checked for codes yet?

 

[NHale623]

First make sure the fuel filter is good, then get a pressure gauge and pop it on the fuel rail and grab a reading. If i remember correctly (someone please correct me if my memory has failed me) an acceptable pressure reading should be within the range of 30 to 45 PSI on the rail. If it's low, then you have to figure out if it's the FPR, or the pump (usually the pump)

For a '95 4.0L OHV engine, the specs for fuel pressure are 28-45 psi with the engine running, and 35-45 psi with the key on and the engine off.

 

[jamester_a]

The Surging Is The Same Cold Or Warm .im Tired Of Tracing This Problem Gonna Take A Few Day Break.then I Might Try Unpluging The 02's.wont That Really Throw The Computer Off?

If the problem occurs when cold then no need to pull 02s.

Marginal DPFE and EGR are also causes of surging.

 

[pontiacdude]

Thanks So Much For All The Recent Responses Fuel Pump Is Less Than A Year Old Ill Check The Filter Im Not Sure What The Fpr Is .the Egr Is Good. What Is The Dpfe ? Excuse My Ignorance ,im A Carpenter Who Knows A Little About Mechanics.

 

[pontiacdude]

Who Gets The Gold Star Nhale623 Or Jamester A For Bringing Up The Dpfe. I Googled Dpfe. Found A Site That Said To Unplug The Egr Vacume And Plug It. If The Problem Was Gone It Ment It Was The Dpfe .i Unpluged It The Surge Was Gone I Am A Happy Camper.now Do I Replace The $45.00 Dollar Dpfe Or By Pass It Like The Site Showed I Could By Putting The Egr Vacume To The Inlet Side Of The Dpfe And Pluging The Egr Tubes Two Lines.thank You Thank You Thank You All. I Hope Its Still Gone In The Morning When I Drive It To Work.

 

[NHale623]

It's part of your emissions, replace it.

I'll guarantee you if you had checked for codes, you would have had one for the DPFE. It won't illuminate the CEL, but it's there. KOEO 335.

Don't ask me how I know.

 

[jamester_a]

Who Gets The Gold Star Nhale623 Or Jamester A For Bringing Up The Dpfe. I Googled Dpfe. Found A Site That Said To Unplug The Egr Vacume And Plug It. If The Problem Was Gone It Ment It Was The Dpfe .i Unpluged It The Surge Was Gone I Am A Happy Camper.now Do I Replace The $45.00 Dollar Dpfe Or By Pass It Like The Site Showed I Could By Putting The Egr Vacume To The Inlet Side Of The Dpfe And Pluging The Egr Tubes Two Lines.thank You Thank You Thank You All. I Hope Its Still Gone In The Morning When I Drive It To Work.

For good measure you might also want to test your EGR valve to make sure it is operable and can hold a vacuum. You can use a hand vac guage or if you are a cheapskate like me - your lungs lol.

Both mileage and emmissions are reasons to keep youe EGR system in shape.