| Author |
Message |
    
Jorge P. Gutierrez, Jr. (Jpg2esq)
| | Posted on Tuesday, February 19, 2002 - 04:31 pm: | 
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My 95 Disco immediately after startup stays at 1000 to 1400 rpm then heads back to normal after a while or after i rev the engine. Should I be concerned? |
Brian Jackson (Nerover)
| | Posted on Tuesday, February 19, 2002 - 06:13 pm: |
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I've never been concerned...
Does it do it for more than 30 seconds or so? |
Jorge P. Gutierrez, Jr. (Jpg2esq)
| | Posted on Wednesday, February 20, 2002 - 09:59 am: |
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not really longer than 30 seconds |
steve hatch
| | Posted on Saturday, March 02, 2002 - 02:53 am: |
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I have a 95 with a similar condition. At start up it revs to nearly 2k before settling down to 1100 where it stays. Problem started after having the heads reworked from a blown gasket.
This may sound dumb buy here goes, what exactly controls the idle, or is it a combination of many things? Better yet, what can I do to change the idle speed,and is there a mechanical adjustment available to correct it?
I may come back with a question regarding vacuum hoses routing and functionality...But I'll wait.
Steve |
jpitman
| | Posted on Saturday, March 02, 2002 - 08:15 am: |
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The idle is controlled by two things - a bypass passage (with a screw adjuster), and the stepper motor on the plenum, controlled by the ECU. The speed is also affected by the CO setting in the air flow meter, but less directly. The screw adjuster is under a plug on the plenum rear of the throttle plate - takes an allen key around 5/32? Book procedure is:-
-plug bypass to stepper motor fitting to stop stepper doing anything
- ensure engine up to operating temp
- get good external tacho on coil
- remove plug, fit allen key
- adjust idle to 525 +/- 25 rpm -may vary for USA?
- refit plug, open up bypass hose.
In my experience , this MAY produce excessive idles while moving, as you decelerate - 'flaring' its called I think. I just adjusted the screw inwards (clockwise) to reduce this effect. The ECU is supposed to use the stepper to hold 750rpm, but it can get into trouble - there are some service bulletins on this problem, related to AC switching in/out etc. If your air flow meter is set rich (high CO, ~1.9V) the flaring seems worse - I reduce mine to 1.5V, seems to spin better, not flare or move around so much.
YMMV |
E Snyder
| | Posted on Saturday, March 02, 2002 - 10:55 am: |
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Had the same high idle problem at start-up with my 95, replaced the stepper motor (idle air control valve) and it went away. |
Steve Hatch
| | Posted on Saturday, March 02, 2002 - 01:28 pm: |
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I will look into the stepper motor, and also do the prescribed adjustment procedure as explained in the previous post. Thanks for the detail, I have been looking for some good info after my mechanic gave up and told me I needed a new emission control circuit, I didn't think so...
Thanks Again,
Steve |
Brian Friend
| | Posted on Saturday, March 02, 2002 - 10:32 pm: |
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Steve,
check your stepper motor. Takes about 10 min. to remove. clean it up with carb cleaner real well. Also check your mass air flow connections. I was stalling on steep inclines. Stepper motor fixed that. Then mymass aiflow became disconected was just a loose connection. tightened it up and no problems since. bty...after you clean the stepper motor your truck will run realweird untill all he carb cleaner is burned out then it will run fine. |
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