Stops at 3000 rpm - help!

[hmhaga]

My sister has a 1998 Explorer 4.0 SOHC (204 bhp). When under light load, the engine won't pass 3000 rpm. I can floor the pedal or put the tranny in 2. gear, but it still refuses to go much higher than 3000-3100 rpm. I can feel no hesitation or juddering, it just stops accelerating. Downhill, it'll pass 3000 rpm - but very slowly. It'll happily run past 60 mph, but only at low revs.

I'm not used to automatics, but as far as I can judge - the tranny up- and downshifts as expected.

The idle manifold pressure is too low, below the "bad" value indicated in the servicemanual. I guess this indicates an airleak - but where? Any typical places to look?

The problems occured after an engine repair at a local Ford dealer (to cure camchain noise), afterwards they've been totally UNABLE to correct the problem.

Any feedback highly appreciated!

 

[gijoecam]

I'd start with the simple stuff myself. First, check to see if there isn't a floor mat bunched up under the accelerator pedal. (It happens a LOT!!! car wash will pull the mats off the hook, vacuum them, and just toss them back in.... it shifts around and bumches up)

Second, check that the butterfly in the throttle body is actually opening all the way. It should be very close to horizontal when you floor the gas pedal. If it's not, you'll need to find out why: Bent gas pedal (not likely) stretched cable (they don't usually stretch THAT much, but you never know), or maybe something else is restricting the movement of the pedal or throttle body linkage.

Now, if both of those are fine, I'd start with the fuel filter. It's probably the simplest thing to correct of all the possible causes, and if it hasn't been done recently probably is needed anyways.

If one of those three don't pan out, let us know and we'll see what else we can dig out of our bag of tricks.

-Joe

 

[i8u]

What were your vacumm readings at idle and at a steady 2000 rpm? Was the needle steady or did it fluxuate between a set of numbers? What do the readings do when you hold it at 2000rpm at let go of the throttle so that if falls back to idle? Note the readings durring this procedure .

 

[i8u]

As mentioned defenately check the linkage first....

 

[i8u]

Oh yeah... I remember a tsb on the axcellerater cable......

 

[hmhaga]

Oh no....it was the floor mat! It now kicks down one additional gear, and runs to 6000 rpm with no problems. Thanks! ;-)

There _is_ a vacuum leak, I guess this also have influence on the tranny? As a cause of the leak, the accelerator pedal has to be pressed down further than usual to build enough vacuum and cause kickdown?

Can the throttlevalve in the throttlebody cause loss av vacuum? The black coating is worn off, but there is an adjustment screw. I'll attach a turbo boost meter (reads down to 1 atm neg) to read the vacuum levels.

 

[Sl3pySnorlax]

I'd start with the simple stuff myself. First, check to see if there isn't a floor mat bunched up under the accelerator pedal. (It happens a LOT!!! car wash will pull the mats off the hook, vacuum them, and just toss them back in.... it shifts around and bumches up)

Second, check that the butterfly in the throttle body is actually opening all the way. It should be very close to horizontal when you floor the gas pedal. If it's not, you'll need to find out why: Bent gas pedal (not likely) stretched cable (they don't usually stretch THAT much, but you never know), or maybe something else is restricting the movement of the pedal or throttle body linkage.

Now, if both of those are fine, I'd start with the fuel filter. It's probably the simplest thing to correct of all the possible causes, and if it hasn't been done recently probably is needed anyways.

If one of those three don't pan out, let us know and we'll see what else we can dig out of our bag of tricks.

-Joe

I am having the same problem and all three are good any other suggestions

 

[410Fortune]

Check intake plenum o rings

 

[Fix4Dirt]

on mine the IAC y pipe piece leaked replaced w/ an L no issue sine it'd occasional go into limp mode and idle high, though i suspect its not your issue, since its nto in limp or idling high.

 

[donalds]

The rev limiter in park and Neutral is 3000 rpm so I'd see if the Neutral safety switch is adjusted proper

 

[donalds]

We've been duped this thread is from 2005 lol