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  #1  
Old 10-08-2011, 11:52 PM
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Default Engine revs up randomly only when moving in neutral 2.5l

I own a 99 Ranger 2.5l 2wd 5sp.

Ive done some searching but Ive found nothing that matches my exact problem.

Im was thinking it was the idle air bypass valve (i believe its called) but its brand new. So what happens is as im driving on the highway doing 60 ill step on the clutch and the engine will rev up to a steady rpm on its own, like 3000-4000 rpm. Then Ill shift into the next gear and step on the clutch again to change gear yet again, and same thing with the rpm's. It will do this until I come to a complete stop. It will rear its ugly head tipically once the truck is well warmed up and mosly in heavy traffic.

Whats the deal with that one?

Any suggestions would be delightfull.

Thanks
Gabe
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  #2  
Old 10-08-2011, 11:56 PM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

IAC valve. or a vaccum leak
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  #3  
Old 10-08-2011, 11:59 PM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

Or a throttle cable obstruction.
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  #4  
Old 10-09-2011, 12:14 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

Ill check for leaks..... Thanks pooleo.

94mtx,

When its occurring ill give the gas pedal a couple of wacks in neutral and it will rev up as it should when you step on the gas but will then rev down to the exact same 3000-4000 rpm's. Gas pedal will return to full rested position. Feels very precise like an engine management issue not a mechanical (cable) issue if that makes any sense.

Thanks,

Gabe
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  #5  
Old 10-09-2011, 12:20 AM
;p
 
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

If nothing else, perhaps you have the throttle screw set too high!
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  #6  
Old 10-09-2011, 12:28 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

Well Ill take a better look at it in the morning.

I figure I ask so I can narrow the searching.

Thanks for the tips.

Gabe
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  #7  
Old 10-09-2011, 07:42 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

-make sure the CEL comes on KOEO

-try and catch a pending code

-start doing tuneup/maintenance issues. ie, vacuum leaks, clean TB, MAF, pcv, etc

----------

Quote:
Originally Posted by rangergabe View Post
I own a 99 Ranger 2.5l 2wd 5sp.

Ive done some searching but Ive found nothing that matches my exact problem.

Im was thinking it was the idle air bypass valve (i believe its called) but its brand new. So what happens is as im driving on the highway doing 60 ill step on the clutch and the engine will rev up to a steady rpm on its own, like 3000-4000 rpm. Then Ill shift into the next gear and step on the clutch again to change gear yet again, and same thing with the rpm's. It will do this until I come to a complete stop. It will rear its ugly head tipically once the truck is well warmed up and mosly in heavy traffic.

Whats the deal with that one?

Any suggestions would be delightfull.

Thanks
Gabe
Did you have the issue before you replaced the Idle air control valve(bypass valve)?
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  #8  
Old 10-09-2011, 07:42 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

Throttle position sensor would be my guess. In order for it to rev up like that, it needs air and fuel. A stuck IAC or vacuum leaks would be allowing in more air but the fuel would not increase to keep up with it. Also since it sounds like it has picked a rather consistent RPM to increase to, I thin that further points to the TPS.
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  #9  
Old 10-09-2011, 09:23 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

I picked up the truck 2 weeks ago so I didn't replace the IAC my self the previous owner did. I can tell its new because its damn shiny and I have a recipe for it, the owner threw in the glove box.

The CEL comes on as it should through KOEO.

It has been throwing code P0401-insufficient EGR flow. Could this be connected?

Thanks

Gabe
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  #10  
Old 10-09-2011, 09:26 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

I don't see how any egr problem would cause the problem you're describing. Maybe the IAC is installed wrong or something is jamming it open?
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  #11  
Old 10-09-2011, 09:30 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

P1401 is very common most of the timeit is the DPFE sensor, but first clean out the EGR valve and check the hoses to the DPFE. If no luck replace the DPFE
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2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).

1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).
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  #12  
Old 10-09-2011, 09:42 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

What is the location of the DPFE? and how much does it run?

Thanks

----------

Is there a way of cleaning/checking this sensor before replacement?
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  #13  
Old 10-09-2011, 09:54 AM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

I doubt this the issue but check that the IACV connection is good and that the guy put a gasket on it. He prob had this issue and replaced the IACV to no avail, but it best to check anyways
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2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).

1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).
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  #14  
Old 10-09-2011, 02:57 PM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

DPFE is probably gonna be a metal box (for your year, they upgraded to plastic later on) on the exhaust/passenger side next to the last cylinder. It has two rubber hoses connected to the bottom of it which leads to a tube that connects to your exhaust manifold. Has an electrical plug on the box.

Run about 50-60 bucks.
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  #15  
Old 10-10-2011, 08:50 PM
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Default Re: Engine revs up randomly only when moving in neutral 2.5l

I really haven't had much time to play with this since I spent all weekend dealing with a motor mount fiasco.

But again thanks for the tips and ill definitely report back my findings.

Gabe
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