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surge at idle when warm

ben/sherry

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Messages
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City, State
LOUISVILLE
Year, Model & Trim Level
1996 ford explorer
I have a 1996 explorer sport 4.0L 4x4 . The engine surges at idle when in "D" or "R" . Some times the surge is mild and other times it feels like it is going to quit running . Back in January I had the problem , I was asked to check the vacuum hoses and I found that the "PCV" hose was collapsing. I changed it and my problem went away untill now . I have checked all vacuum hoses again and also smoked checked the engine for vacuum leaks and could find no leaks . There are no codes , I have checked fuel pressure when running and it is good , Changed all 3 O2 sensors with motorcraft parts , no help . Any help would be appreciated !!
 
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fast_dave

Explorer Addict
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City, State
East Bay - Nor Cal / PRK
Year, Model & Trim Level
'98 Spt 4.0 OHV 5 spd 4x4
@ben/sherry

Just to clarify, is your Ex surging in D and R when your foot is on the brake or?
 
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ben/sherry

Member
Joined
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Messages
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LOUISVILLE
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1996 ford explorer
It surges all the time even with the foot on the brake or off the brake when engine is warm . if your foot is off the brake and just idle on the driveway , it will just lunge.
 
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fast_dave

Explorer Addict
Joined
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Messages
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City, State
East Bay - Nor Cal / PRK
Year, Model & Trim Level
'98 Spt 4.0 OHV 5 spd 4x4
@ben/sherry

My Ex has the same OHV engine that yours does - here's two of the most popular issues.


More than likely it sounds like unmetered air (another term for a vacuum leak) is entering your intake system.
The likely culprit is the three (3) upper intake gaskets (aka Intake Plenum Gaskets) need to be replaced (NOTE: Only one (1) is pictured BUT you need three (3).

For a number of reasons, this can be a tough area to find a vacuum leak - but on average I'd say these gaskets have a service life of about 5 years on a daily driver.

Fel-Pro 90733 is the part number for a three pack @ Rock Auto for $3.40

PG54_Front__ra_p.jpg



OR

BUT - there have been cases where the IAC (Idle Air Control) valve is sticking (or on the fritz) - and needs to be cleaned or replaced.
There's a black plastic "piston" that runs back/forth inside of the IAC that gets coated with exhaust gas and thus gets sticky - throwing off the idle speed.

BUT before you pull the IAC valve, try this - pull the black plastic "pill" on the IAC valve and see how your Ex runs.
That "pill" is really a mini air filter, and it's been my experience that over the long haul it can get clogged with fine dirt particles...
With a lil' tiny screwdriver work, it can be opened up, and the "pill" shaped filters can be removed and cleaned.
If after pulling the "pill" your Ex runs better BUT isn't fully cured, try cleaning the IAC.
That MAY cure it OR ultimately you might have to buy a new one.

Hitachi ABV0069 is the factory OEM and it's $52.79 @ Rock Auto


Use the search feature: lots of info on the forum how to remove and clean the IAC valve.
(2) 10mm bolts to remove it, a can of carb cleaner, and clean Q-Tips.

F5TZ9F715BA-ANG__ra_p.jpg




Here's a Rock Auto 5% off Discount Code: 13432995153839345

howHear.jpg


Enter the discount code in the 'How Did You Hear About Us?' box without any other numbers or characters for an additional 5% savings.

Welcome to the forum, good luck & report back to close the loop!
 
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ben/sherry

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Joined
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Messages
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City, State
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1996 ford explorer
Thank you very much !! I checked the IAC valve and everything looked good . I rechecked all my vacuum lines again , I do think that my next step is replacing the upper intake gaskets !! I have only 88,000 miles on the car . Thank you for the part numbers !! That will save me some time !! Do you know a good video or manual that has the correct way to take the upper manifold apart ? I really do appreciate your help and also everybody else on this forum !!
 
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fast_dave

Explorer Addict
Joined
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Messages
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Reaction score
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City, State
East Bay - Nor Cal / PRK
Year, Model & Trim Level
'98 Spt 4.0 OHV 5 spd 4x4
@ben/sherry

With this part - the miles don't matter as much as the length of time the super thin rubber gaskets are compressed by having about 13-15 pounds of intake manifold/coil pack vibrating and heat cycling on top of them. Anything over 5 years and you're getting into the "red zone"...

When you remove the upper intake manifold (the black plastic part) and you see how little these o-rings "hang/come down" - you'll get it ;-)

Due to their low cost (ONLINE @ Rock Auto) I advise that you buy yourself (6) gaskets total - 3 for the repair and three to keep for a future repair.

For instance - they're always good to have when you have to separate the upper intake manifold from the engine to change the valve cover gaskets ;-)

The OHV valve cover has a tendency to leak on BOTH the rear/bottom areas of each valve bank; Cyl 3 & 6.

Valve Cover Gaskets: Fel-Pro VS50368T for $23.79 a pair @ Rock Auto.

SFL_VS50368T_P04_TOP__ra_p.jpg


NOTE: MOST auto part shops charge DOUBLE for these valve cover gaskets - might as well get a set of these as well and save on shipping...

OK - Here's a good thread w/ Pictures click on the link/blue writing to the right >: How to replace upper intake manifold gaskets

No magic on my part with regards to the parts numbers; The more you work on your Ex, you'll find that Rock Auto has the BEST & MOST ACCURATE catalog of parts - USE IT!!! Additionally, they have many pictures/views of each part offered - a VERY VALUABLE tool.

Again - welcome, don't be a stranger, take pics and report back!
 
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ben/sherry

Member
Joined
January 25, 2020
Messages
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City, State
LOUISVILLE
Year, Model & Trim Level
1996 ford explorer
Thank You very much Fast Dave !! I am ordering the parts to day and thanks for all the info !! It is very helpful and informative !! I plan on doing the gaskets as soon as I get them . I watched the video , it is easy to understand , I should not have any problem ! i will take my time !! Thanks very much !!
 
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fast_dave

Explorer Addict
Joined
June 6, 2005
Messages
1,238
Reaction score
549
City, State
East Bay - Nor Cal / PRK
Year, Model & Trim Level
'98 Spt 4.0 OHV 5 spd 4x4
@ben/sherry

A couple of last minute suggestions.

Pictures:
Sometimes, these jobs take a little longer than planned; I take pictures during the disassembly process.
That way, if some time passes, you have a reference/map when putting things back together.

Nuts & Bolts:
Utilize old /used zip-loc bags and label them with a Sharpie.
Make notes on the bag for the occasional LONGER bolt and where it goes.

Painters Tape (I prefer yellow):
HIGH visibility to help with reassembly - with your Sharpie, mark each end of disconnected vacuum lines and electrical connections so you don't miss anything when you're tired during reassembly. A simple numbering system - i.e. 1 & 1, 2 & 2, 3 & 3 so it's all plug and play.

Special Tools:
To properly torque the nuts holding down the plastic upper intake manifold, due to circumference clearance issues with the plastic manifold, you will need a 1/4" drive 13mm Deep Well/long metric socket and long 1/4" drive extension "shaft".

A 3/8" drive 13mm socket & extension CAN be made to work BUT due to clearance issues you won't be "square" to the nuts and thus you won't be torquing them properly.

Cleanliness:
A can or two of aerosol carb cleaner OR brake cleaner and a good supply of old CLEAN tube socks turned inside out so you're using the high nap side OR old high nap cotton dish towels are your best friend...

HOOD:
If you're going to tackle the three (3) Upper Intake Gaskets as well as the Valve Cover Gaskets at the same time, take off the hood.
You can do the job without removing the hood - BUT - as someone who has been there and done that - it's so much less frustrating to do with the hood removed.
You get tons of light in your engine compartment, you don't have to crouch and get back aches, and you head isn't constantly hitting the underside of the hood.
The hood is made out of aluminum and weighs maybe 25 - 30 pounds.
Make "witness marks" on the four (4) hood bolts and hinges - in relation to where they are assembled, so everything lines up when you put the hood back on.
 
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ben/sherry

Member
Joined
January 25, 2020
Messages
17
Reaction score
2
City, State
LOUISVILLE
Year, Model & Trim Level
1996 ford explorer
@ben/sherry

A couple of last minute suggestions.

Pictures:
Sometimes, these jobs take a little longer than planned; I take pictures during the disassembly process.
That way, if some time passes, you have a reference/map when putting things back together.

Nuts & Bolts:
Utilize old /used zip-loc bags and label them with a Sharpie.
Make notes on the bag for the occasional LONGER bolt and where it goes.

Painters Tape (I prefer yellow):
HIGH visibility to help with reassembly - with your Sharpie, mark each end of disconnected vacuum lines and electrical connections so you don't miss anything when you're tired during reassembly. A simple numbering system - i.e. 1 & 1, 2 & 2, 3 & 3 so it's all plug and play.

Special Tools:
To properly torque the nuts holding down the plastic upper intake manifold, due to circumference clearance issues with the plastic manifold, you will need a 1/4" drive 13mm Deep Well/long metric socket and long 1/4" drive extension "shaft".

A 3/8" drive 13mm socket & extension CAN be made to work BUT due to clearance issues you won't be "square" to the nuts and thus you won't be torquing them properly.

Cleanliness:
A can or two of aerosol carb cleaner OR brake cleaner and a good supply of old CLEAN tube socks turned inside out so you're using the high nap side OR old high nap cotton dish towels are your best friend...

HOOD:
If you're going to tackle the three (3) Upper Intake Gaskets as well as the Valve Cover Gaskets at the same time, take off the hood.
You can do the job without removing the hood - BUT - as someone who has been there and done that - it's so much less frustrating to do with the hood removed.
You get tons of light in your engine compartment, you don't have to crouch and get back aches, and you head isn't constantly hitting the underside of the hood.
The hood is made out of aluminum and weighs maybe 25 - 30 pounds.
Make "witness marks" on the four (4) hood bolts and hinges - in relation to where they are assembled, so everything lines up when you put the hood back on.
Thank you for the advice !! I was planning on using painters tape to mark everything . I am hoping to get on it next week . My grand daughter slightly smashed the front end on her edge , I have been tied up repairing it . Thanks for everything !!
 
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