B

bille

Guest

• Jun 7, 2005

• #1

My 1989 Jeep seems to lose power when the weather is warm or hot. It runs
fine during the 60 mile drive to work in the morning, but about 1/3 to 3/4
of the way home it loses power when it is warm or hot. If the weather is
cold it runs fine. The MAP, CPS and CTS have been replaced, compression
is fine on all 6 cylinders. If I disconnect the vacuum line to the MAP, it
has the power, but surges (gas mileage also drops). It passed emissons
testing and usually gets ~ 19 to 21 MPG. It also takes a long cranking
time to start it (warm or cold).

 

W

Will Honea

Guest

• Jun 7, 2005

• #2

On Tue, 7 Jun 2005 00:11:41 UTC "bille" <bill@billerhard.net> wrote:

> My 1989 Jeep seems to lose power when the weather is warm or hot. It runs
> fine during the 60 mile drive to work in the morning, but about 1/3 to 3/4
> of the way home it loses power when it is warm or hot. If the weather is
> cold it runs fine. The MAP, CPS and CTS have been replaced, compression
> is fine on all 6 cylinders. If I disconnect the vacuum line to the MAP, it
> has the power, but surges (gas mileage also drops). It passed emissons
> testing and usually gets ~ 19 to 21 MPG. It also takes a long cranking
> time to start it (warm or cold).

The long crank time is typical of the 87-90 I6 with the Rennix
computer. I would wonder what your temp guage is doing when it loses
power - could this be either an overtemp thing or a bad temp sensor
messing up the computer? 60 miles in the morning should have it
easily up to operating temp, even on cool mornings so I would be
looking at overheating - thermostat, fan clutch, clogged radiator, bad
temp sensor.

--
Will Honea

 

S

SnoMan

Guest

• Jun 7, 2005

• #3

"bille" wrote:
> My 1989 Jeep seems to lose power when the weather is warm or
> hot. It runs
> fine during the 60 mile drive to work in the morning, but
> about 1/3 to 3/4
> of the way home it loses power when it is warm or hot. If the
> weather is
> cold it runs fine. The MAP, CPS and CTS have been replaced,
> compression
> is fine on all 6 cylinders. If I disconnect the vacuum line to
> the MAP, it
> has the power, but surges (gas mileage also drops). It passed
> emissons
> testing and usually gets ~ 19 to 21 MPG. It also takes a long
> cranking
> time to start it (warm or cold).

How warm are we talking here when the power starts droping and are you
using the air when it happens?

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B

bille

Guest

• Jun 7, 2005

• #4

SnoMan
The air is not on when it loses power, the temp is usually above 70
degrees.

 

B

bille

Guest

• Jun 15, 2005

• #5

Will
The temp gauge shows normal temperature, and the AC is not on. MAP, MAT,
and CTS are new, connections to sensors have been cleaned, air filter is
new.
When it starts losing power, I just pull over and disconnected the vac.
line to the MAP sensor and it it has plenty of power, but lopes when it is
idling. Fuel filter has been replaced.
Any more ideas?

 

W

Will Honea

Guest

• Jun 15, 2005

• #6

On Wed, 15 Jun 2005 11:11:16 UTC "bille" <bill@billerhard.net> wrote:

> Will
> The temp gauge shows normal temperature, and the AC is not on. MAP, MAT,
> and CTS are new, connections to sensors have been cleaned, air filter is
> new.
> When it starts losing power, I just pull over and disconnected the vac.
> line to the MAP sensor and it it has plenty of power, but lopes when it is
> idling. Fuel filter has been replaced.
> Any more ideas?

If unplugging the MAP sensor makes a noticable difference, especially
an improvement, I would suggest checking the vacuum hose to the sensor
and the port it plugs into on the throttle body. On my '88, that
little sucker was plugged solid. I used a small drill bit, lots of
cleaner, then a pipe cleaner to finally get it unplugged.


--
Will Honea

 

B

bille

Guest

• Jun 15, 2005

• #7

Will,
I checked the line from the MAP sensor - it is clear. A vacuum guage
shows ~ 18 in vac. and the reading is steady. What could this be????

 

W

Will Honea

Guest

• Jun 16, 2005

• #8

On Wed, 15 Jun 2005 20:03:40 UTC "bille" <bill@billerhard.net> wrote:

> Will,
> I checked the line from the MAP sensor - it is clear. A vacuum guage
> shows ~ 18 in vac. and the reading is steady. What could this be????

Does the vacuum change as you goose the throttle and let off quickly?
You have two contrary indications here: the performance improves when
you pull the vac line off the tb, yet it shows a high vacuum (is that
at either end of the tube?). One thing says the MAP is responding to
changes in vacuum, the other says it isn't. You might be able to tell
if the MAP is actually doing it's job by applying a hand vac pump to
the line just to see how it reacts - could even be a wierd ground to
the sensor or a dirty connector.

--
Will Honea