I have a 1990 grand marquis 5.0 and I am trying to identify a part.
It is located at the top of the middle of the firewall directly behind
and above the engine, looking at the engine from the front grill.. It
is black plastic with one or two small gauge vacuum hoses going into
it with a wired harness also.
I am not sure but I think it is a "module" named part with a three
letter abbreviation name. I had a digram of it but lost it.
Thanks for any help!
another question. I have changed just about every sensor already,
including the IAC TPS and the EGR valve with the solenoid sensors and
the coolant temp sensor. I still get a minor hesitation from a dead
stop on initial drive of the day and sometimes I get a hunting idle.
I was getting a steady check engine light to start with but replacing
the IAC did away with that and I gave the throttle body a good
cleaning. Now I get a check engine light for a fraction of a minute
one out of every 10 starts. All codes that I had I cleared and none
appear now either.
I was told the MAP sensor could be the last resort causing this
problem. I can't say for sure but I think that changes in the weather,
hot and humid, dank and damp, afffect this problem also.
Would I be wasting my time changing the MAP or do you think it is a
Your problem with erratic idle is usually related to either
a bad IAC or a vacuum leak. The off idle stumble sounds
more like a bad TPS or signal from the TPS circuit. Maybe
it has a bad connection or it is not at the correct idle
voltage signal. Has anyone tried to set the idle speed with
the stop screw on the throttle body? This is a frequent
cause of erratic idle and off idle stumble. The stop screw
must be set exactly by the book. A maladjusted stop screw
will result in incorrect idle signal from the TPS. I think
you are shotgunning it with parts instead of diagnosis. For
the cost of a MAP sensor, you should be able to get a good
diagnostic scan done by a pro to find out what it is doing
and, the MAP sensor is not likely to cause erratic idle or
stumble as you describe. Has anyone done a fuel
pressure/delivery test? That vintage sometime experienced
fuel pressure regulator problems that resulted in a rich
mixture which can cause some of these problems.
Thanks for the detailed reply.
Today I first took the car to my mechanic and checked for any codes.
There were none.
Next I went and purchased a new TPS and I will be putting it in later
today. I am hoping this problem ends here with the new TPS. I will
post after the repair and update the situation.
Thanks for the reply.
No, it doesn't burn a drop of oil. I have it since it was new and it
runs fine, except for this recent problem. I still get approx. 25 mpg
on the highway with just 132,000 total miles.
Installed the new TPS about an hour ago and so far the hesitation
problem has not happened but I really had no time to drive around to
really check it. I'll know more tomorrow keeping my fingers crossed.
It would be nice to finally get rid of this problem.
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