Re: MAP Sensor "Issue"

From: Bernd D. Ratsch (bernd@texas.net)
Date: Tue Apr 18 2000 - 08:40:23 EDT


Hey Shane,

Yup...it's a V6. I haven't checked the MAP readings on my original one yet
to see where they're at...but a gut feeling told me that this is the problem
from the very start of the whole "Pinging Dakota" problem. (Along with a
slightly too aggressive timing curve for the average daily driver.)

- Bernd

-----Original Message-----
From: owner-dakota-truck@buffnet.net
Subject: Re: DML: Re: MAP Sensor "Issue"

Boy thats interesting - especially considering it cured my pinging problem
also. New intake, wires, wire reroute, thermostat, plugs, combustion
chamber
cleaner, etc. all would not do a thing for it. Only the MAP sensor - and I
picked up massive performance increase all across the rpm range. Not only
that
but when I swapped my bad MAP into my wifes "never pinged" truck - it
started
pinging like an SOB.

Here's what I found re: replacements. If you go into Autozone, PrepGurls,
Advanced Auto or one of the high volume "discount" places, they will tell
you
that the part costs $85-$90 and is not in stock. Some will even say they
can
not even get it. Others will say it can be gotten thru some kind of
"special
order" which takes a few days (same price). Write down their part number
and
have them look up a MAP sensor for a '93 Dak w/318 - it will be the same
part
number and much cheaper (around $50). This is also a "special order" item.
If
you go down to NAPA - they list part number EC1629 (Echlin part) for both
Rams
and Daks w/V8s. Price here in Nashville's NAPA was $67.88. I bought that
one.
Of the three MAP sensors that I have (2 original from my 2 trucks and 1 new
from
NAPA) all looked identical and had the same first 2 numbers and a different
last
number. The bad one had these 3 numbers: 56026770, 64469D, 0396DJ. The
brand
new one had these 3 numbers: 56026770, 64469D, 2855AP. I assume the first 2
are
different from Bernd's because he has a V6 (I think - right Bernd?) and they
must be slightly different. I can get closeup pix of all three of mine if
it
helps.

Some values obtained from my scan tool on the three MAPs are as follows.
Remember this is a range of operation over at least 30 miles running in the
mountains with a good mix of loads applied. Also, keep in mind that these
are
relative to ambient pressure - hence the name Manifold ABSOLUTE Pressure. I
understand that they read 0-1 bar = 0-100 Kpa = 0-29.5 in-Hg. I assume this
also translates to 0-5V or 0.2 - 4.8V according to my voltmeter.

1.481-7.996 in-Hg (Avg 3.423) < this is a 4 year old presumably working MAP
sensor
6.515-29.021 in-Hg (Avg 12.296) <- this was the bad MAP sensor
1.481-9.180 in-Hg (Avg 3.745) <- Brand new MAP sensor

I'm also pretty sure that the check engine light that related to a bad MAP
sensor is for values too high which makes sense according to these findings.
Can someone confirm this? My reference materials are outside and its cold
out
and I'm still in my pjs and barefoot 8-).

Once I put good MAP sensors in my two trucks - they BOTH are now running
like
raped apes. I'm a very happy camper for sure.

Latr,

Shane

ps - someone please double check my figures here as I'm still waking up and
have
only had 1 cup of coffee so far 8-)) Maybe we can put this MAP-related
pinging
stuff to bed once and for all. I'm still amazed at how much difference a
good/bad MAP can make.



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