88 F-150 4.9 EFI runs rich

On Sun, 23 Dec 2007 23:41:18 -0600, David Coleman rearranged some
electrons to say:


No, there isn't.   But it almost certainly means something is broken.
Is the check engine light on?

No engine light on. It does come on when I turn the key on, but goes out
once the engine starts. It takes on average, 5-10 seconds of cranking to
start. I can smell the richness either cold or warm engine temp.
Let me get one of the readers and see if it gives any errors

I _think_ your truck is OBD I (on board diagnostics, level one), and you can
buy a code reader for your truck for about $35. AutoZone will pull codes on
an OBD II car or truck for free, but I don't know if they offer the same
service to OBD I, I suspect they do not but you can ask.

I think your Check Engine light should be on, with the problem you are
having. The Check light should come on every time you turn the ignition ON,
and should go out again when the engine starts. This is a Self Check
sequence that confirms the light works. When a problem crops up, the light
should come on again. You need to confirm the light works, because if it
does not work, then it should be on right now telling you there is trouble.
If it does work, but is not on, then I'd still pull codes and reset the
computer.

There are a couple of things that control the mixture, the Idle Air Control,
the O2 Sensor, engine temperature, to name a few. Troubles with these things
should throw a code and set the Check light on.

There is no mechanical adjustment -- idle screw to twist on, jets to play
with, those sorts of things -- for your trouble.

Ok. I did the code testing and here are the results:

1.) Code 32 - EGR pressure backfeed fault
2.) Code 42 - HEGO (H2)S) Voltage hight/System rich
3.) Code 52 - Power steering pressure switch open

So since it shows a fault with the EGR, is that what I need to replace? And
what is with the power steering pressure switch? I've noticed no problems
with the power steering.

Some of the codes could be generated long ago, and I'd ignore the power
steering for now. Reset the codes and test again to see what comes up -- you
can pull codes later today, or in a week (or both) -- and see if the power
steering fault comes back, then deal with it then.

I think the EGR is your fault today. The Code 42 is reporting conditions you
already know about -- the engine is running rich -- but the Code 32 is
reporting a condition that can cause the Code 42. Does that make sense?

The EGR itself can be okay, and your trouble is with the control circuit to
it -- which is operated by heat or vacuum, I forget which. In any case, you
should investigate the EGR control side, and if there is anything wrong
there it should be reasonbly obvious. If you do not find anything, then you
need to make a trip to the parts store.

Personally, I have never had an EGR problem, so I can't say with any
conviction what the cause can be.

I assume that if you reset the codes, and took a ride to the parts store and
pulled codes again, the Code 32 would be there again. Indeed, it could be
there immediately upon starting the engine again. Sometimes it helps to know
when the code comes up. I had a '95 Bronco and the Check light would come on
in the middle of a trip, and eventually go off and not come back again for
the remainder of that trip. It turned out I had problems with the O2
Sensor -- I don't recall the code. In any case, I could reset the codes,
drive around, and the code would not repeat until the Check light came on
again. Any stored code would remain, even if the Check light went out. The
operation of the O2 is such that if it comes back into spec, the fault is
turned off (the Check light goes out), then the light comes back on if the
fault repeats.

I'm a bit perplexed that you have noticable gas fumes and no Check light.
Since the main job of OBD I is to monitor emissions stuff, emitting massive
quantities of gas should trigger a response.

PS
Did you buy the code reader, or use it for free at Autozone?

I bought it myself. So it is brand new and should have nothing in the memory
So do you think I need to replace the ECG ?

No. I think you need to replace the EGR. I think the EGR is vacuum
controlled, and you may only have a cracked hose.

Code 32;
Wrong code definition for code 32.  Pressure sensors weren't used
in 1988 on the 4.9 trucks.
Your code 32 is a "pintle position sensor error."
On top of the EGR valve is a position sensor, it is a basic
potentiometer, the EGR closed sensor voltage should be under 1.0
volt, if carbon is holding the EGR pintle off of its seat, that
-could- set the code.
You can backprobe the EGR signal wire with a DVOM and determine
what the at rest sensor voltage is.
Vacuum leaking past the EVR (EGR control solenoid) could also
allow the EGR to open at idle and set the code.
May be worthwhile to R&R the EGR and see if the pintle is seated
as it should be.
EGR position sensors are/were high failure items.
(back in the 80s in the dealership, we jokingly referred to code
32s as "pass codes.")

Code 42;
This can be caused by a number of things.
An EGR valve stuck open will raise manifold pressure causing the
engine to run rich based on an erroneous MAP sensor signal.
Skewed MAP sensor.  The MAP sensor reports the wrong altitude
and/or wrong intake manifold pressure.  Testing requires a meter
capable of reading frequency, the frequency measurement is then
compared to the altitude chart that Ford publishes.
Air pump.  When the engine is cold, the air pump flow is sent to
the exhaust manifold or cylinder head upstream of the oxygen
sensor, when the engine reaches operating temperature, air pump
flow is directed downstream to the catalytic convertor or is
bypassed to atmosphere.  If the air pump fails to switch when it
should, the O2 sensor sees a lean exhaust, the ECU then commands
more fuel resulting in a rich condition.  Pinching off the rubber
tubing upstream of the O2 sensor will usually prove or disprove
this failure.
Leaking fuel pressure regulator.  One side of the fuel pressure
regulator diaphragm is exposed to manifold vacuum, if the
diaphragm leaks or is ruptured or torn in any way, raw fuel is
then sucked into the intake manifold resulting in an extremely
rich condition.
Shorted O2 sensor, if the 12 volt heater should become shorted
internally to the O2 signal, the voltage signal to the ECU will
be high which is an indication of rich fuel mixture, the ECU will
lean out the fuel delivery and believe it or not, extremely lean
and extremely rich smell pretty much the same to the human nose.

Code 52;  P.S. switch only used on vehicles with automatic
transmissions.  Could be a false code if wrong ECU is used on
manual transmission vehicle.  Could also be false code if you
performed a engine running self test and did not cycle the
steering wheel when prompted.  Could also be a bad P.S. switch
but would normally be accompanied by a complaint of low idle
speed or stalling when performing tight steering maneuvers at low
engine speed.

Also; your check engine light is not set up to notify you when
there is a problem or when codes are being stored.  It is only
wired to the STO circuit which means the only time it will come
on is during bulb test and when a code reading device is
connected,   i.e., STI and STO connected in diagnostic mode.

On Mon, 24 Dec 2007 12:37:50 -0600, "David Coleman"


I would not worry about the EGR or steering codes.  Don't
shoot the messenger on the EGO sensor either.  It is telling
you what you already know - it is rich.  This means it must
be working in the right direction.  Known problems in that
vintage include fuel pressure regulator failures.  The
nature of the failures results in a rich mixture especially
at lower speeds.  The hard starting is likely a result of a
rich mixture and plug fouling.  Pull the vacuum hose to the
regulator.  If there is fuel in the hose, it is a goner.  If
no fuel check the fuel pressure.  I don't recall the correct
pressure for the six but, I think it was in the mid 30's
range at idle.  Another problem that frequently crops up is
the ECT sensor which will not set a code until it is
completely dead.  It can be checked for resistance with a
meter to see if it is obviously out of range.

Good luck
Lugnut

well on the 88 ford its the eec system not obd,

and code 32is the evp sensor on top of the egr valve
(did you goose the throttle in koer test?)  if not tha will set code 32

code 42 is its runnung rich

code 52 (did you turn steering wheel from stop to stop i koer test  if
not that will set it)  with engine running dissconnect the red vac hose
from the fuel press reg and if gas comes out(not good) if the egr was
stuck open it would not idle very good then the isc would take over and
raise the idle to about 2000 rpm then back down and sometimes stall(that
can be taken off and ceaned out ) but do check the map senser  they do
al kinds of funny stuff when the go bad,,,jst find one from a friends
car our truck in the 87 to 90 range and plug in and see if thats it
,,just dont start to through parts at it,,that   costs money ,,hope this
helps

No I did not reve the engine...


Nope...didn't do that either...wasn't worried about the PS unit


I changed the MAP sensor about a year and a half ago, then again about 6
months later as it had failed. This time I bought a lifetime warrenty MAP.


The engine does "lug" at an idle. But not up to 2000 rpm. I think normal
idle is like 800. It usually only varies by 200-300 rpm. Enough to be
noticeable and
enough to be a aggravation and embarrassment.

Granted this truck is almost 20 years old, but I just put a new engine in it
about 2 years ago and other than this problem, it runs great. I live in S.
Texas and would not be afraid to drive it to either coast and back without
doing more than just a oil change before I left. So I would hate to get rid
of it, or worse, just park it.

I appreciate all the help you guys are giving me. I am sure we will get this
problem fixed. I am going to replace the EGR valve and hoses (to be safe)
and see what that does

On Sun, 30 Dec 2007 22:50:08 -0600, "David Coleman"


You can replace the EGR if you want. It is your money. But,
consider this: If the EGR is closed at idle as it should be,
it does no effect normal engine operation or fuel mix.  The
job of the EGR is to dilute the intake air charge with
exhaust gases to reduce combustion temperatures and reduce
NOX emissions.  It has the effect of leaning the mixture.
You are now too rich which probably means you have a
different problem.  Save your money and look for a problem
that will cause a rich mixture instead.  I would look for
vacuum leaks before doing anything. A vacuum leak to the MAP
sensor would be sure to cause a bad signal and rich mixture
just like a bad MAP sensor.  A bad FPR or a vacuum leak to
it would be a sure cause.  A bad ECT or ACT sensor would be
a sure cause.  Vacuum leaks can be elusive.  You must be
patient when looking for them.  I suggest using something
like carburetor cleaner when looking for vacuum leaks to
spray on any suspect area.  BTW, what you are looking for is
not an intake manifold vacuum leak.  Those cause high or bad
idle accompained with lean readings.  You are looking for a
sensor related leak or a bad sensor.

If you want to test the EGR for effect, use a piece of
vacuum hose to jumper vacuum to it from the extra port on
the intake.  Watch what happens when you apply vacuum.  If
the engine runs diferent, the EGR is working properly.  The
EVP sensor may not be working correctly but, that will not
give you a rich mixture.  IT usually results in a slight
surge at light throttle in the mid range.  Changing the EGR
is getting the cart before the horse.

 if its  throttle body, the injector may have an o-ring around it
leaking, look for the drip .lucas

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