1998 Explorer 4L Dangerous High RPM Surge

tinkering · July 20, 2014

1998 Explorer 4L 6Cyl 4WD 5 Speed Auto

This engine unexpectedly surges from idle up to as much as 3 or 4 thousand RPM. It can be frightening. The IAC valve was buzzing loudly so we changed it out a couple of times with wreckers parts. With the third replacement valve in there, it hasn't surged yet but we are very leery to drive it for fear of uncontrolled acceleration while in heavy traffic. Is this a known problem or recall with these vehicles. I think it is ridiculous that the design would allow such a dangerous condition!

colintrax · July 20, 2014

No recall, stuff happens. I'd replace the IAC first. I had the same thing happen when my battery crapped out, and when my positive came loose. However those caused other issues as well.

tinkering · July 20, 2014

I found a list of recalls here:http://www.motortrend.com/cars/1998/ford/explorer/recalls/

I found hundreds of underhood fire, and unexpected runaway acceleration Complaints here:http://www.carcomplaints.com/Ford/Explorer/1998/engine/

I am not going to replace the IAC valve with a used wreckers part. With such obvious safety hazard potential, I am going to replace it only with a new top quality manufacturer part, like Standard brand.

"stuff happens" is not good enough for me as far as these vehicle flaws are concerned. The recalls listed in the above link should all be addressed, like the bad Cruise Control cable, the sticking/freezing throttle plate, and a fusible link installed into the CC switch harness circuit. I do not remember all the details of all the repairs but they are listed in the above links.
There have been very many fires, accidents, and injuries attributed to these flaws, and one death that I read of. It is not to be taken lightly. :roll:

Turdle · July 20, 2014

tinkering said:
I found a list of recalls here:http://www.motortrend.com/cars/1998/ford/explorer/recalls/

I found hundreds of underhood fire, and unexpected runaway acceleration Complaints here:http://www.carcomplaints.com/Ford/Explorer/1998/engine/

I am not going to replace the IAC valve with a used wreckers part. With such obvious safety hazard potential, I am going to replace it only with a new top quality manufacturer part, like Standard brand.

"stuff happens" is not good enough for me as far as these vehicle flaws are concerned. The recalls listed in the above link should all be addressed, like the bad Cruise Control cable, the sticking/freezing throttle plate, and a fusible link installed into the CC switch harness circuit. I do not remember all the details of all the repairs but they are listed in the above links.
There have been very many fires, accidents, and injuries attributed to these flaws, and one death that I read of. It is not to be taken lightly. :roll:

Could be a maintenance issue. Low coolant, or, overheating will cause the engine to rev in attempt to cool it down.

How many miles on your 16 year old car?
Did you buy it used? When?

tinkering · July 20, 2014

Turdle said:
Could be a maintenance issue. Low coolant, or, overheating will cause the engine to rev in attempt to cool it down.

How many miles on your 16 year old car?
Did you buy it used? When?

Coolant is up; temp gauge reads good.

250,000 Km or 156,000 Miles on it.
Just recently bought it used. The Check Engine Light is on (I am shopping for a scanner) It has a K+N air intake on it; could that be the trouble; should I put the stock air back on?

swshawaii · July 20, 2014

tinkering said:
The Check Engine Light is on

Scan for trouble codes FIRST. K&N oiled filters have been known to contaminate MAF sensors, wouldn't hurt to clean it.

http://www.explorerforum.com/forums/showpost.php?p=2054355&postcount=2

tinkering · July 20, 2014

swshawaii said:
Scan for trouble codes FIRST. K&N oiled filters have been known to contaminate MAF sensors, wouldn't hurt to clean it.

http://www.explorerforum.com/forums/showpost.php?p=2054355&postcount=2

Thanks for that.
I can't wait to purchase a scanner and see what codes are on there.
Can you clean a MAF sensor, or do you mean clean the K+N?

swshawaii · July 20, 2014

Clean the MAF first. Most larger auto parts stores will scan trouble codes FREE, call around. Remember to write down the numbers.

Many MAF cleaning threads, here's just one. Search.
http://www.explorerforum.com/forums/showpost.php?p=1970170&postcount=4

Turdle · July 20, 2014

Yes. You can have the codes scanned, free of charge. They do this in hopes of selling you an oxygen sensor-

Do have the codes scanned and write them down . post back up your findings please. That is the only place to start.

Cleaning the maf sensor is a good idea, however any actions you take before knowing what the computer is telling you is almost like running in circles.

tinkering · July 20, 2014

swshawaii said:
Clean the MAF first. Most larger auto parts stores will scan trouble codes FREE, call around. Remember to write down the numbers.

Many MAF cleaning threads, here's just one. Search.
http://www.explorerforum.com/forums/showpost.php?p=1970170&postcount=4

Thanks for all of that :salute:

I have an old scanner that I bought for our 86 Taurus. It says it will do some Ford Lincoln Mercury vehicle systems 1992 and newer. It is an Actron Sunpro CP9015. Do you (or anyone) happen to know anything about that one? I will see if I can find online a complete list of F L M vehicles and systems it will cover.

swshawaii · July 20, 2014

Agree. Scanning for codes is the very first thing to do after a CEL is thrown. Anything else is guessing.

Note: 1996 and newer vehicles are OBD II compliant and require OBD II compatible products such as the
PocketScan Code Reader CP9125, PocketScan Plus CP9410, the SUPER AutoScanner CP9145 or CP9150 Kit.

http://www.actron.com/product_detail.php?pid=16153

tinkering · July 20, 2014

swshawaii said:
Agree. Scanning for codes is the very first thing to do after a CEL is thrown. Anything else is guessing.

Thanks. I just found that Actron link. The CP9015 misses the the OBD I by 2 years. That's OK. I was looking at getting a 9580 or 9580A; that is probably more economical in the long run, than getting a F L M specific scanner?

drdoom · July 21, 2014

Check to make sure someone hasn't been monkeying with the hard idle screw. Also you can try an IAC pipe restrictor insert which is homemade by inserting a one inch length of 3/8" fuel line into the intake end. I tried this for a while and it made little improvement.

tinkering · July 21, 2014

drdoom said:
Check to make sure someone hasn't been monkeying with the hard idle screw. Also you can try an IAC pipe restrictor insert which is homemade by inserting a one inch length of 3/8" fuel line into the intake end. I tried this for a while and it made little improvement.

Thanks for that. It doesn't seem like the hard idle screw but I will look at that.
The original IAC valve was actually broken, I put a small plastic cup (off of the coil spring of a 6V lantern battery

with a small orifice hole drilled, directly into the valve opening; it fit PERFECTLY. It brought the idle right down; it worked well to get us 250 miles home. Now I want to get the whole thing settled though with the correct parts, and the Check Engine light out. For safe motoring, I think all of the sensors/components need to be backing each other up.

tinkering · July 22, 2014

We put a brand new IAC valve in. 'Standard' brand $116.88 before tax. I am VERY surprised that THE CHECK ENGINE LIGHT WENT OUT!

:biggthump
My new Actron 9085A will be here in a couple of weeks so the scan will still happen. I will post to let you know if anymore high RPM runaway problems occur.

tinkering · December 6, 2014

Well, the check engine light came back on. The engine surged again majorly. It is very mind rattling on snow and ice:thumbdwn: It surges regularly at idle between 750 rpm to 1200 rpm +\- In the old days that could indicate a lean condition. I suppose it can still be the case with todays computer controlled engines?
I scanned the codes with my new Actron CP9580A. The only codes that came up were P0171 Bank 1 System Too Lean and P0174 Bank 2 System Too Lean. The 'Top Reported Fix' is "Replace Intake Manifold Gasket". This unit had a K+N air intake system installed before I bought it. Before I start changing intake manifold gaskets I'm thinking of putting the stock air intake back on; before I do either of those two things I am going to change the fuel filter. Does anybody know where the fuel filter is located?

Turdle · December 6, 2014

tinkering said:
Well, the check engine light came back on. The engine surged again majorly. It is very mind rattling on snow and ice:thumbdwn: It surges regularly at idle between 750 rpm to 1200 rpm +\- In the old days that could indicate a lean condition. I suppose it can still be the case with todays computer controlled engines?
I scanned the codes with my new Actron CP9580A. The only codes that came up were P0171 Bank 1 System Too Lean and P0174 Bank 2 System Too Lean. The 'Top Reported Fix' is "Replace Intake Manifold Gasket". This unit had a K+N air intake system installed before I bought it. Before I start changing intake manifold gaskets I'm thinking of putting the stock air intake back on; before I do either of those two things I am going to change the fuel filter. Does anybody know where the fuel filter is located?

In the driver side frame rail under the driver seat.
Do change the filter, but plan on the upper and lower intake gaskets to fix the lean codes.

ALso , while you are in there check the PCV line elbows for leaking.

lobo411 · December 6, 2014

tinkering said:
This unit had a K+N air intake system installed before I bought it. Before I start changing intake manifold gaskets I'm thinking of putting the stock air intake back on; before I do either of those two things I am going to change the fuel filter. Does anybody know where the fuel filter is located?

It's not the cold air intake.

Runnin'OnEmpty · December 6, 2014

tinkering said:
......Does anybody know where the fuel filter is located?

It's located on the inside of the frame rail near where the
driver sits. Your lean codes are probably caused by
faulty plenum gaskets though...

tinkering · December 8, 2014

Runnin'OnEmpty said:
It's located on the inside of the frame rail near where the
driver sits. Your lean codes are probably caused by
faulty plenum gaskets though...

By faulty 'plenum gaskets' you mean intake manifold gaskets?

1998 Explorer 4L Dangerous High RPM Surge

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