99 4.0 sohc wont exceed 2000 rpms | Ford Explorer Forums - Serious Explorations

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99 4.0 sohc wont exceed 2000 rpms

Frustrated9

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Year, Model & Trim Level
1999 ford explorer
Help 99 explorer 4.0 sohc ran fine then one day wouldn't rap above 3000left then foed "expert" said cut off cats to see if it would then. Now only 2000 rpms. Replaced fuel filter, pump, throttle position sensor, and map still only 2000 rpms. thought if i sprayed starting fluid while reving would at least no if it was fuel delivery issue. Bad idea! Killed it like shutting it off and now wont start at all need help or good offer on a parts wagon for someone
 



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Usually a failed Mass Air Flow MAF sensor will put the engine into lamp mode, limiting the RPM's. Did you scan for error codes?
 












Replaced mas air flow sensor too before the starting fluid incedent
 






Any rondom ideas would be greatly appreciated! Or if someone wants it for parts please leave a message
 






It might be worth pulling the air intake hose off of the throttle body, and lodging the accelerator down to the floor (with the vehicle off) to make sure the throttle body is opening all the way. I remember reading that the cable can slip, limiting the mount of travel. It's quick and easy to check...
 






Tps?
 






Replaced mass air flow sensor throttle positin sensor idle control fuel filter fuel pump and fuel tank vapor pressure sensor due to slipping of jack after replacing fuel pump finally got a code of lean mix on left bank checked fuel pressure at fuel rail was 65 psi with no bleed off still at a loss as to what to try next any ideas?
 






Explo SOHC won't run

Help 99 explorer 4.0 sohc ran fine then one day wouldn't rap above 3000left then foed "expert" said cut off cats to see if it would then. Now only 2000 rpms. Replaced fuel filter, pump, throttle position sensor, and map still only 2000 rpms. thought if i sprayed starting fluid while reving would at least no if it was fuel delivery issue. Bad idea! Killed it like shutting it off and now wont start at all need help or good offer on a parts wagon for someone

I had similar problems with the Anti-Deceleration Valve during high temperature (above 90 ambient) that was similar to what you describe -- it would not generate any power, it would not rev. Disconnecting the Anti-Decel valve told me that this was the problem - which is one of the 2-wire electrical connectors you must disconnect if removing the plastic air intake on top of the SOHC engine. The valve itself is about 1-1/2 inches around. You can disconnect this valve and the engine will run; if you notice a difference in performance with it disconnected, then that is your problem.
The valve is about $100 to replace. I did not try to modify to run without it, I just determined what was 'wrong' and replaced it. It was an elusive thing to find because - in my case - it had to be over 90 degrees outside and after about 5 miles of driving before I would get the problems. (I thought it was fuel starvation, etc... considered all the options.)

I hope that helps.
 






A couple more thoughts...
The troubles mentioned with on my 99 Explo XLT 4wd SOHC -- I'm on my 4th Explorer now with my 2001 Sport. My engine would run with or without the Anti-Decel connected (you said yours 'wont run' now). Once I had it in 'fail' mode, when it was too hot and presenting the problem (a few times broken down at the side of the road) it would start and idle fine with the bad valve connected, but would not rev, had no power. If I were to then disconnect the two-wire harness connection to the valve, it would have a rough and uneven idle, but at least it regained the ability to rev more-or-less-normally.

When it was nighttime and cooler, or just stayed below 90 outside, I had to reconnect the 'bad' valve (with no bad side effects) to keep a smooth idle.

I took it to the dealer, and they could not find it, two different times (but, it was never above 90 degrees when I had it at the dealer).

It drove me nuts for about two months, 'til I stumbled upon it.

Again... good luck.
 






It does run starts right up and runs great till it hits 2000 rpms then just hesitates dosent die and held throttle body open by hand its opening all the way
 






Also checked fuel rail pressure its at 65 psi. Timing as read by scanner is 20° at idle and 28° at 2000 rpm
 






No more ideas from me

Sorry, I don't have any more ideas on this one.
My experience was maybe 5 years ago , and to be honest, I've not even popped the hood on my 2001 2-door Sport (which is my winter beater) in 6 months.
Good luck.
 






Put exhaust back together now raps up to just over 3000 rpms will try replacing intake gaskets cause they're cheap $17 hope that is the ticket but will find out this weekend. Wish me luck!
 






Disconnect the maf sensor and see how it runs with out it . it will go into default mode. I know you replaced it already just see how it runs without it Also you stated it has fuel psi at 65 is that an idle check or at 3k when its dying.
 






65psi at idle climbs to 70 at three and holds steady even as motor starts hesitating. Holds 65 psi even after shut down. Will try unhooking maf and see what happens will let you know
 






plugs, plug wiring & compression

I suggest that you check the spark plugs and while you have each plug out check the compression. Also, check the spark plug wiring.
Cylinder%20key%204_0%20SOHC.jpg

Pay particular attention to cylinders 5 and 6.
 






Replaced all plugs they looked good when i took out old ones. Never switched any wires. When it runs it runs good just wont run above 3000 rpms. Rained all day so had no chance to work on it will try tomorrow. Thanks.
 






I just noticed something with my 2001 SOHC 4-liter -- it won't rev above 3000 RPM if it's not in gear -- such as, when parked, or in the driveway. It revs right up to 3000, but hits a rev limiter of some kind if not in gear. (I never noticed that before on any others). But, if I put it in drive and go, it'll rev up to 5500 RPM without any problem (I only tried it on level ground, and just can't go any faster on this stretch of road).

With the Explorers, you need to be sure EVERYTHING is as it's supposed to be -- doors closed, seat belts on, weight on the seat, etc. They do spooky things, too...
- I know of weird things like, the radio will cut out (for no obvious reason) while driving, and shifting from drive to neutral and back to drive, and the radio would come right back on. Did it every now and then. Don't know why. Had that in my 99 SOHC 4wd.
- I know that the wipers would make one intermittent pass on its own schedule when in drive, and for a while I thought it was only when I made a right-turn such as pulling forward and to the right out of a parking spot. Again for no apparent reason, periodically, one of the other two 4-doors.
I remember test-driving a 2000 or so Mountaineer and I started it up and the wipers made a pass after about 20 seconds (for no reason). I shut it off and walked away from it. I don't need this spooky stuff.
- And I know there's some kind of relay or mechanical wiring device right above the driver's head in the headliner that clicks (like a micro reed-relay sound) but I never tore it apart to find it - and I didn't see anything in the wiring diagram at that area. It was just annoying. It would just go on (click) and off (click). So, I turned the radio up.

Good luck.
I'm trying to close up the rear end and put new rear brakes on my 2001 Sport tonight. Front brakes tomorrow. Got 1500 miles to go this weekend with it.
 



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as far as it revving to 3000 rpms in nuetral or park this is normal it is a setting in the pcm to engage rev limiter when in nuetral so you cant blow the engine and it switches to a higher rpm when in gear.
as far as your electrical concerns they are just that electrical concerns and not normal operation on any explorer I have owned 4 different explorers and I am a senior master ford tech for 25 years I can assure you your veh were broken and not operating as normal.
back to the veh at hand have we ever unplugged the maf and see if it changes this 3000 rpm limit. also try just for the hell of it put it in manual 2 and see if it still is limited.
 






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