Oil pressure light ON when warm and idling

Our teenager has been driving our '96 Stratus ES (now with 72K miles)
for the last year, and we lost track of when the last oil change had
been done (he or one of his friends had removed the reminder sticker).
As soon as we discovered that it had been 13 months and 7000 miles (!!),
we got it serviced.

Now we find that, once the engine is warm, the oil pressure light goes
on when the engine is idling, but it goes out again at normal driving
speeds.

Is this something needing drastic action? What about some kind of oil
additive? Or have them use a heavier oil next time? Or...? (Suggestions
of physical violence to our teenager are not acceptable.)

BTW, the gas gauge has also started behaving erratically. Is there
perhaps a single electrical fault that could could cause the oil
pressure light to come on as well? (I could more easily understand a
fault that would keep the light off when it should be on, but...)

Perce

 

See my recent post on this problem. Get the oil pressure switch
checked and have the actual oil pressured measured at the shop while
you're at it.

http://groups.google.com/group/rec.autos.makers.chrysler/browse_thread/thread/e0d4842d876c2704

Phil

 

More then likely the oil sending unit is at fault. you can have the pressure
tested and replace the sending unit if that's the problem, also disassemble
the connector and remove the rubber seal from the top and clean out all the
dirt and oil from it or it may still turn the lite on.

Glenn Beasley
Chrysler Tech

 

I will admit that I was once a stupid teenager and did the exact same
thing, only to an '89 Buick LeSabre, around 1994'ish.

....and, the exact same thing happened to me on the Buick! The oil
pressure idiot light would come on while at a stop or while idling, and
then go out again once I gave it some gas. Later still, the light was a
little bit more insistent about staying on, until finally it stayed on
most of the time, only flickering slightly at highway speeds and higher
RPMs.

Sadly, my stupidity and ignorance about car care and maintenance at the
time was compounded by having parents who were... frugal. So when I
mentioned the problem to the 'rents, m'dad muttered something about an
oil pressure sensor going bad, checked the oil level, and upon seeing
all appeared fine, gave it his blessing, so I shrugged and kept driving.

Two days and about 100 miles later, the engine finally seized.

Turns out, the oil pump had given out, probably from having to move all
that sludge created when the oil changes were neglected. This condition
wasn't so detectable when the oil was nice and thick, but once that
slurry was finally changed for the fresher stuff, the overstressed and
weakened pump became a huge problem.

Suffice it to say that upon noting all the resulting costs, the
experience became an expensive but well-learned lesson, and I've become
a Maintenance-Nazi on all cars I've owned since.

(Incidentally, the same frugal 'rents later gave me an experience and a
nice story to tell about how you should never "fix" a broken hood latch
on a '94 Dodge Caravan by strapping the hood down with a bungee cord
affixed to the grille, but that's material for another thread.)

Heh. I'd definitely get it checked out. Maybe it IS an oil pressure
sensor in your case. But the fact that the oil pressure light is coming
on after severe neglect of an oil change convinces me that it should get
looked at sooner rather than later. Unless of course, your teen has the
bucks to spend on a new engine, or wants to buy a new car.

That seems very unlikely. That might be a coincidence. Perhaps your
teen's been putting in very cheap gas, too?

 

Your good intentions and important lesson learned notwithstanding, a
one-time 7000 miles between oil changes is nowhere near the degree of
neglect needed to cause noticeable oil pressure issues on that engine,
plus this is a common occurence on the Chrysler pressure switches - they
start leaking internally and that throws their trip point off to the
point that they think they sense low pressure and start flickering in
the worst-case warm-idle-in-gear situation when, in fact, the oil
pressure is fine - classic sign of needing a new sensor switch. (I
think they call that a run-on sentence, but what the hey...)

*BUT* (and that's a BIG BUTT) - as you suggest, it might not be a bad
idea to also have the pressure checked - just in case.

Definitely agreed on that - no connection between the two problems.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

7000 miles is a perfectly normal oil change interval. 3000 miles is
wasteful and unnecessary, especially with modern oils and
double-especially with synthetic oils.


That depends on the root cause. If the oil pressure is actually low, it
could be indicative of excessive bearing wear. The engine won't drop
dead immediately if the oil pressure still comes up at normal speeds,
but it would indicate that the engine is tired.

However, given the history of the electrical oil pressure sending units
that chrysler used through the 90s, its much more likely just a bad
sending unit.

Absolutely NOT. While thickening additives can make the light go out,
wat they do is trade more pressure for less FLOW of oil through the
system. That's not a good trade- if the oil is FLOWING at 0 back
pressure, the engine is getting better lubrication than if the flow is
being restricted to cause measurable backpressure.


Or have them use a heavier oil next time?

Stepping a "tired" engine up too something like 20w50 is OK, but again
you're trading lower flow for the false security of higher pressure.
Just make sure they don't put an oil that is thinner than the
recommended oil for your engine. With the number of newere engines that
take 5w20, and 0w30 type oils its going to get more and more likely that
the Jiffy Gloob type places will put too-thin oil in older cars.

 

I had exact same problem on my Cirrus 2.5L. Dealer replaced the sending
unit for $97 and still had problem. I then replaced PCV valve for $5 and
haven't had a recurrance for almost 12 months.

 

I wouldn't worry too much about a 72k car like the OP's and a 7000
mile oil change, but it is foolish to assume that the best oil change
interval
is a constant throughout the vehicle's life.

Older, looser engines have a lot more blowby and the oil's detergents and
such get used up faster. Older engines also tend to burn more oil and can
easily go through 2-3 quarts over 7000 miles. Most people, particularly
people who take cars to places to get oil changed, are not going to check
oil levels consistently in between changes on a 7000 mile change, and
letting it get lower than a quart and a half creates a huge amount of wear.

Oil is still at a buck a quart, I just got a flyer from the local
Schucks/Checkers/Kragen
for Valvoline at 99 cents a quart. I buy Purolator Plus oil filters on sale
at the local sports and auto supermarket for about $4 a filter, thus
making my cost to do an oil change about $10. And I see the local
Jiffy Lube places putting coupons for $20 oil changes in the paper all
the time.

Assuming a vehicle lifespan of 200,000 miles, at 3000 mile change
intervals, @ $20 a change, that is a grand total of $1300.00
By doubling the time between changes to 7000 mile you are
only saving $660.00 which is about 4% of the purchase price
of a $15,000 vehicle that you are going to be driving for about
15 years, assuming an average of 14,000 driven miles a year,
or about $47 dollars a YEAR in savings.

And that's if your PAYING someone to do oil changes, if you
do them yourself like I do, the savings is only about $24 A YEAR.

But go on, save yourself money. But you just remember something -
the next time you slam on the brakes and stomp on the gas all the
way to work because your pissed that your girlfriend didn't give you
a hand job, keep in mind your doing more than $24 worth of wear
and tear to your car. If you drive like 90% of the drivers on the road,
your a big hypocrite because the miles and years your taking off that
vehicle is far, far more than the piddly amount your saving with an
extended change interval. If you want to save money, learn to
drive like an old Grandma before you get your tit in a wringer over
squeezing the last drops of cash out of your oil.

Ted

 

I don't see how it is posible that a PCV valve could have *any*
significant affect on oil pressureg - maybe a coincidence that some
cause happened to go away about the same time the valve was replaced.
Anybody have a credible argument for that being the case.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Sorry, but its IMPOSSIBLE for the PCV valve to affect oil pressure like
that. I suspect that in replacing the PCV valve, they bumped a wire to
the sending unit. Or its a coincidence.

 

I noticed that when vehicle was warm and sitting at a stop light, the idle
was around 500 rpm, which wasn't quite normal. It had previously been about
700 rpm. Also, if I just stepped on gas lightly, the oil light went out.
So, I theorized that the motor wasn't idling quite high enough for normal
oil pressure. Replacing the PCV valve seemed to work for me. This "fix"
has been mentioned by others in this group before. But it anyone thinks I'm
out to lunch, don't try this $5 fix.....