1986 Jaguar XJS looping at idle

Tiny
JES2FUNY2
  • MEMBER
  • 1986 JAGUAR XJS
Engine Performance problem
1986 Jaguar XJS V12 Two Wheel Drive Automatic 140k miles

lopes at idel speed, sometimes dies.I set the idle up to 12k and it went away, but to high to drive this way, especially in snow! It runs great down the road, but at a stop it lopes in gear and out. Have flushed fuel lines, replaced pump, new plugs
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Saturday, December 19th, 2009 AT 12:25 PM

4 Replies

Tiny
DAVE H
  • EXPERT
Hello .. thanks for the donation .. much appreciated

Try checking all vacuum lines for leaks/damage etc.


http://www.2carpros.com/forum/automotive_pictures/266999_jag_39.jpg



Hope this helps


http://www.2carpros.com/forum/automotive_pictures/266999_AAA2_919.png

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Saturday, December 19th, 2009 AT 3:40 PM
Tiny
JES2FUNY2
  • MEMBER
I had nalready checked and replaced the vacuum lines, must not have shown in the question. Any other ideas? Replaced fuel pump, flushed lines, new air filters, checked vacuum lines and replaced all. Still looping at normal idle. Thanks Kevin
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Sunday, December 20th, 2009 AT 1:40 PM
Tiny
JES2FUNY2
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Please read question again this is the third time I have received the same answer. If you do not know please refund my money.
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Wednesday, December 23rd, 2009 AT 5:46 PM
Tiny
DAVE H
  • EXPERT
Sorry it took so long to reply .. busy at work and the run up to Xmas .. you need to check the MAP sensor is working correctly !

ELECTRONIC CONTROL UNIT (ECU)
The ECU utilizes an integrated circuit containing the digital fuel injection control chip and an analog-to-digital converter to translate information from the sensors. The fuel injection program is stored in a Read-Only-Memory (ROM) chip.
For any given manifold pressure and engine speed combination, the memory provides a fuel injection duration for optimum combustion. The ECU also monitors other sensors to modify the basic speed and pressure signals so that cold starting, mixture adjustment and other areas of engine operation can be controlled.

ENGINE LOAD SENSING
As the airflow entering the engine varies, the pressure in the plenum changes. This change in pressure is monitored by the manifold pressure sensor. The manifold pressure sensor sends a signal that indicates the degree of engine load to the ECU.
The manifold pressure sensor is fitted with a separate diaphragm to compensate for changes in barometric pressure. The manifold pressure sensor is located in the ECU and is connected by a hose to the intake manifold balance pipe.

MANIFOLD PRESSURE SENSOR (MPS)
Disconnect the battery. Pull the connector from the MPS. Using an ohmmeter connect test leads between the terminals. Compare resistance readings to specifications.
If readings are not to specification, replace the MPS. Reconnect the MPS connector and battery.
MANIFOLD PRESSURE SENSOR RESISTANCE
Terminals...........................Ohms
7 & 15...............................85.5-94.5
8 & 10...............................346.5-353.5
7 or 15 & Ground.................0
8 or 10 & Ground.................0

Manifold Pressure Sensor.....At right front corner of engine compartment.


http://www.2carpros.com/forum/automotive_pictures/266999_jag_40.jpg



Hope this helps


http://www.2carpros.com/forum/automotive_pictures/266999_2carxmas2_21.jpg

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Thursday, December 24th, 2009 AT 3:53 AM

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