On 6/19/2025 4:58 PM, UFO wrote:

Just got a 1998 Ford F150 with the V6 / Auto about 100K
miles. Not sure when its had a tune up, but occasionally at
a light the idle will reduce as if its about to stall, then
it recovers.

Recently I let the vehicle sit a few days without a start
and it started up fairly quick, but soon the idle slowed
down quite a bit again, nearly stalled.

Some internet research says it could be an EGR valve and
other things like the coil pack module?

I was gonna try some STP fuel injector cleaner maybe as a
start....any good resources out there of this engine?

Start at any mechanic or auto parts store to read the codes.
Write them down and research solutions (Adjustment?
Replacement?) once you know where the problem lies.

--
Andrew Muzi
[email protected]
Open every day since 1 April, 1971

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Just got a 1998 Ford F150 with the V6 / Auto about 100K miles. Not sure when its had a tune up, but occasionally at a light the idle will reduce as if
its about to stall, then it recovers.

Recently I let the vehicle sit a few days without a start and it started up fairly quick, but soon the idle slowed down quite a bit again, nearly
stalled.

Some internet research says it could be an EGR valve and other things like
the coil pack module?

I was gonna try some STP fuel injector cleaner maybe as a start....any good resources out there of this engine?

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UFO <[email protected]> wrote:

Just got a 1998 Ford F150 with the V6 / Auto about 100K miles. Not sure when >its had a tune up, but occasionally at a light the idle will reduce as if
its about to stall, then it recovers.

Well, first step is to do a basic tuneup, do a check for vacuum leaks,
clear the codes, drive around and see what codes get set. With a '98
you get computer control but without so much ability to look inside the computer control.

But... if you don't know what the plugs are like and you don't know if there are vacuum leaks and the fuel filter might be the original one that came
with the car, you should at least get the car up to good driving condition before attempting any diagnosis.

Some internet research says it could be an EGR valve and other things like >the coil pack module?

Maybe a plastic Jesus might help too. Do actual diagnosis.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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I guess I will need a ODB code reader? Will any one do or only the older
ones?

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On 6/20/2025 4:00 PM, Scott Dorsey wrote:

In article <[email protected]>,
UFO <[email protected]> wrote:

I guess I will need a ODB code reader? Will any one do or only the older
ones?

Maybe. 1998 was a transition year... california cars all had OBD-II,
some trucks had OBD-II, but some cars and trucks still had OBD-I. Check
the manual if you don't see an obvious OBD-II port. You may be having to count light flashes.
--scott

Since he mostly needs to know why it's not running well, he
should probably just use the (usually free) code reading
services rather than buying a reader at this point.

--
Andrew Muzi
[email protected]
Open every day since 1 April, 1971

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In article <[email protected]>,
UFO <[email protected]> wrote:

I guess I will need a ODB code reader? Will any one do or only the older >ones?

Maybe. 1998 was a transition year... california cars all had OBD-II,
some trucks had OBD-II, but some cars and trucks still had OBD-I. Check
the manual if you don't see an obvious OBD-II port. You may be having to
count light flashes.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

--- SoupGate-Win32 v1.05
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In article <1034ilk$8jua$[email protected]>, AMuzi <[email protected]> wrote: >On 6/20/2025 4:00 PM, Scott Dorsey wrote:

In article <[email protected]>,
UFO <[email protected]> wrote:

I guess I will need a ODB code reader? Will any one do or only the older >>> ones?

Maybe. 1998 was a transition year... california cars all had OBD-II,
some trucks had OBD-II, but some cars and trucks still had OBD-I. Check
the manual if you don't see an obvious OBD-II port. You may be having to
count light flashes.

Since he mostly needs to know why it's not running well, he
should probably just use the (usually free) code reading
services rather than buying a reader at this point.

He might not even need that.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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Thanks, I got a code reader for 21 bucks at Wallymart.

It fit on the plug under the dash, and with the eng running it indicated: P1537, P1538
Found this post online with some things to look into.

https://www.ford-trucks.com/forums/498733-codes-p1538-p1537-what-is-it.html

Meanwhile, I replaced the serpentine belt as the used car dealer had ordered
it
and said I could have it.

I noticed a slight clicking coming from near the alternator area on the pass side
after the new belt was on and eng running. As the eng warmed up, the
clicking seemed
to diminish, almost sounded like a bearing in the really early stages of
EOL.

Previously I had noticed an RPM drop when idling at a light one time, seemed like
it was gonna stall but fully recovered quickly.

Last week the truck sat unstarted for 3 days, and it started up ok but
this RPM drop happened after only 15 seconds, then as before, it recovered
fine
and I moved the truck into the workbay and did the serpentine belt job.

Didnt see the RPM drop with the new belt, but it only sat 2 days not 3.

Wondering if it could be the alternator bearing, or the idler or tension
pulley
once in a while binding, slowing down to nearly a stall?

The dealer did say he replaced the tension pulley not long ago, and the old belt had signs
of fraying on the outer edges....?

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Ok did a little more research and youtube viewing.

Apparently the codes point to (2) IMRC valves and if they are bad
you can see idling and fuel economy issues...so that may explain my drop in idle
I noticed, and it does seem at times I get poor gas mileage on occasion.

The RT IMRC is Part No. F65Z-9S514-CC, F65Z-9S514-CB
Cannot find the PN for the LT side, but an ebay seller told me the OEM
Ford valves will almost always have dry rotted diaphrams and are junk
and ought not be purchased...and to go with aftermarket.

In one of the youtube videos, they claim you will hear a clicking sort of
sound near the intake
manifold if these are bad, so that may explain the noise I made not of in
the other post.

Another video claimed replacing the Vacuum Solenoid Purge Valve , PN: F65Z-9H465-CA /
F65E-9H465-CA solved the 2 error codes so I am thinking about buying this
one on ebay:
https://www.ebay.com/itm/364159939529

With 100K on the eng, maybe its worth replacing anyhow?

I guess also a good idea to look at the vacuum lines behind the battery like the other
webpost mentioned in the event its a leaky line.

The Truck was at this used car dealer 12 yrs, mostly sitting waiting to be sold, he ran it every now and then
for short trips to Home Depot to pick up large items as its got the 8 foot
bed, so maybe those diaphrams
did dry rot or crack in there?

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UFO <[email protected]> wrote:

Thanks, I got a code reader for 21 bucks at Wallymart.

It fit on the plug under the dash, and with the eng running it indicated: >P1537, P1538
Found this post online with some things to look into.

Ignore the second code. The first code tells you that the computer thinks
the intake manifold runner isn't moving.

Some engines will use engine vacuum to move these, some will use a servo.
if yours uses engine vacuum, the first step is to check for vacuum leaks
which you should have done already anyway..

The next step is to make sure they do move freely by hand, and THEN to
check out the position switches that let the computer know that they are
open or closed.

Meanwhile, I replaced the serpentine belt as the used car dealer had ordered >it
and said I could have it.

I noticed a slight clicking coming from near the alternator area on the pass >side
after the new belt was on and eng running. As the eng warmed up, the
clicking seemed
to diminish, almost sounded like a bearing in the really early stages of
EOL.

Did you replace the tensioner at the same time as the belt? If you squirt
a little Super-Lube into the tensioner bearing, does the noise stop?

Last week the truck sat unstarted for 3 days, and it started up ok but
this RPM drop happened after only 15 seconds, then as before, it recovered >fine
and I moved the truck into the workbay and did the serpentine belt job.

Have you looked for vacuum leaks yet? You should check plugs too (which
won't be causing any of your problems but is a good idea on a vehicle with
no maintenance history).

Wondering if it could be the alternator bearing, or the idler or tension >pulley
once in a while binding, slowing down to nearly a stall?

No, that has nothing to do with your stalling problem. That is a different issue. Find out why the computer thinks the runner isn't moving.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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Wound up buying 2 new Dorman replacement IMRC's
was gonna try this myself, but theres a lot of stuff to remove to get at
them.

Dropped it off at a service station, he says there are (12) 8mm bolts that
hold the plenium
to the intake and they are corroded pretty bad, cant get any of them to turn without the socket stripping
the head of the bolts.

Not much room to work a drill in there for an EZ-out he says, so hes putting
it back together
and I will I guess try and hunt down another shop or maybe try it myself.

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I did buy this purge valve and had a mechanic put it in while he tried to replace the IMRC's.
He says the 8mm plenum bolts are stripping as he went to remove them, so he gave up
claiming he would do more harm then good but after he changed the purge
valve, theres
clearly an improvement. Apparently that supplies the vacuum to the IMRC's
and the idle is better
and the sluggishness at 3000 RPM happens a lot less often.

I thought about trying to remove the plenum myself and use one of these https://www.ebay.com/itm/226884149548

But I dont know if there is anough room in there for it to fit, says it will grip an 8mm
head or stud.

Also , after the mechanic replaced the purge valve, the check eng lite is
on. Will reset
with OBD, but returns later with the 2 error codes plus a new one
referencing the EGR system.

Another video claimed replacing the Vacuum Solenoid Purge Valve , PN: F65Z-9H465-CA /
F65E-9H465-CA solved the 2 error codes so I am thinking about buying this
one on ebay:
https://www.ebay.com/itm/364159939529

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