coolant temp sensor?

can a coolant temp sensor be bad and make my car run lousy once it warms up,
even if there aren't any codes? I know how to test the sensor with my
ohmmeter,when its cold and then hot,checking the resistance. I just thought
if it was going that I should get some kind of code. thanks Randy

 

What year and model vehicle?

Some vehicles have a single temp. sensor that controls the engine
temperature (by controlling the engine cooling fans) *and* drive the
temperature gage (thru the computer). If that's the case, you can get
some indication of what's going on with that sensor by how the
temperature gage is operating during and after warmup (in conjunction
with other observations, such as operation of the cooling fans, actual
engine temperature as measured by another known good source, etc.).

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

 

Yes it can, a scan tool would be better so monitor what the temp is
actually reading. What is the year, make and model?

Glenn Beasley
Chrysler Tech

 

this car is running bad now ,once it warms up. 1998 dodge stratus es 2.5v6.
I think the cooling fan always ran more then I thought it should. I'll
check it out with my scan tool. thanks


well, now with new plugs,wires,fuel pump, fuel filter, the car still does
not run right. it misses and acts like it's not getting fuel when you step
on it . could it be the coils shorting out under load? I know my repair
manual says I can check the coils with my multi meter but how do you
simulate it under load, if this is the problem. note: there are no codes of
any kind coming up with this problem. I don't want to be a parts hanger but
I had 2 distributors that were bad before,and the last one was changed in
Feb 07. any ideas or checks I can do. would the dodge dealer find the
problem on his expensive equipment? my mechanic friend did the fuel
pump,filter, this weekend and the last distributor in feb 07 and he thinks
it's an ignition problem. I thought I read somewhere if the voltage isn't
right ,then the fuel won't pump? thanks for any info Randy

 

If you had a scan tool you would be able to read what the intake air
temperature is and probably find out it is way to hot once the engine warms
up. This is because your EGR valve is stuck open and allowing hot exhaust to
enter the intake and causing a really lean condition. On a carbureted engine
this would have caused a bad idle, since this engine is fuel injected
directly into the cylinder all you may notice is a higher idle. Disconnect
the EGR valve vacuum line and see if it makes a difference, If the Spring
inside the valve is broken, disconnecting the hose may not make a
difference. You want to take a shot at it? toss an EGR valve on it.

Glenn Beasley
Chrysler Tech

 

Introducing exhaust gas into the intake does not cause a lean
condition. The exhaust gas, being inert, dilutes the air/fuel mixture
and it'll idle like shit whether the engine is fuel injected or not.

 

It will not idle like shit, it may have a slightly higher then normal idle,
Map sensor will compensate for this leak. Take the EGR valve off and the
engine will run at a high RPM. Not a rough idle.(It isn't a carbureted
engine) The pcm will think that the throttle blade is open and
compensate.What do you think the purpose of the IAT (intake air temp) sensor
is used for????? Incoming cold air will cause a richer mixture, now suppose
you have the intake Temp at 180 to 200 degrees from a stuck open EGR valve?
Very lean condition with a possible hesitation an or ping on accel. The
vehicle will run good until it reaches operating temps.

Glenn

 

Run good until it reaches operating temps? With a leaking EGR valve?
Nope!

Taking the EGR off is not the same as the valve leaking exhaust gas
into the intake. Removing the EGR will leave a large vacuum leak that
will cause a high idle, and the PCM will add fuel because of the low
vacuum sensed by the MAP sensor. Leaking exhaust gas into the intake
will cause a shitty idle or stall, because the fuel/air charge will be
too diluted by the exhaust gas to burn properly.

 

Yup, The intake air gets to hot, causing very lean condition

 

With the engine idling, hot or cold, if you pull the EGR open it will
stall. Likely before you're even able to detect an IAT sensor temp
change with your DRB. High temp is not the problem. Lack of oxygen and
fuel is.

You obviously have no idea what EGR does.

 

well i got the car back and it ran fine until i got almost home. then loss
of power, idled rough, and was hard to start once i shut it off. i do have a
new EGR valve assy, i'll put on tomorrow.

 

Install the EGR valve, it will take care of the problem.

 

Tomorrow has come and gone long ago, when are you gonna tell us it fixed it?

Glenn

 

well glenn ,
its not fixed. i have a question for you . when using a spark tester and
turning the engine over,should there be continuous spark at the gap of
tester? when i do it on my #2 plug i can make a one count between sparks.
is this normal?
i thought it spun so fast that it should almost continuous? i also don't
think it's real blue in color. thanks Randy

 

Is this vehicle a no start? I thought it was a hot drivability problem?

 

What you're describing sounds about right. The spark will not be
continuous. You will only get a spark at one cylinder every other
revolution of the crankshaft. Example: If the engine is cranking at
300 RPM you will see a spark every 2.5 seconds at each plug wire.

If it starts & runs, you're probably not going to determine the
problem by looking at the spark. If you suspect an ignition problem,
you really need to connect a scope to see what's going on.

Or you can keep throwing parts at it.

 

An engine cranking at 300 rpm rotates 5 times per second.
Therefore spark will occur every .4 seconds on a single fire and .2 seconds
on a double fire ignition system.

 

this was suppose to be a warmed up car issue now its a no start car issue.
the plugs were wet and looked fouled so i'm putting in new ones. this went
from just a bad fuel pump(so i was told ) to a host of other issues. first
it ran then after a while it ran lousy ,so mechanic friend suspected bad
coil,so reman distributor was put in. then car ran ok until 3/4 of the way
home and it had no power and acted like it was starving for gas. once i
turned it off ,it was hard to start again. this has been a frustrating
ordeal and i'm not, nor do i like parts hanger mechanics. but once my friend
said he wouldn't have given the car back to me if it was bad and i'm on my
own now , i will find the problem through trouble shooting etc. thanks for
all the input and sorry if it seems like i'm going in circles here on my
posts. Randy

 

Yes, I should have said 2.5 times per second.