1992 4.9L Idle problems
Thread Starter
Joined: Sep 2008
Posts: 2
1992 4.9L Idle problems
1992 4.9L V8 Eldorado - Pulled the intake box off, noticed lots of black carbon build up inside the throttle body, intake manifold and all over the throttle body blades. Used throttle body cleaner on two different occasions to clear this build up off, and the engine began to run much better, initially. Then the idle became faster and faster. When warming up, the engine idles fine at 1000rpms or so, which is to be expected, but once it hits temperature, it was idling at 1500rpm to 1800rpm. Then adjusted the stop screw, where the throttle linkage actuates the blades, got the idle down to an acceptable 800rpms when warm. Now, it still idles fast, but it appears to be ambient temperature dependent...when its hot outside (80-90* F), it idles fast, but when its cool outside (< 70*), it idles at 800rpms.
Also when it idles high, it trips the check engine light, but no Autozone around here has a OBD1 reader. When it idles low, no CEL. Tried disconnecting the battery to clear the ECM, but problem still the same.
Any ideas whats going on?
Also when it idles high, it trips the check engine light, but no Autozone around here has a OBD1 reader. When it idles low, no CEL. Tried disconnecting the battery to clear the ECM, but problem still the same.
Any ideas whats going on?
Junior Member
Joined: Aug 2008
Posts: 27
From:
RE: 1992 4.9L Idle problems
I had a `92 eldo that my bro` now has. I had intermittent probs similar to yours with it. I just had intake plenum replaced for similar prob on my 01 etc.
If I were to pretend to be a tech, I`d look into same, or other vacuum issue.
Pressing "Off" and "Warmer" gets you into your dash OBD to pull codes. I`ll guess the techs here will ask for. You probably shouldn`t be messing with mechanical adjustments as the ecm, I believe, controls such as idle speed, unless it or sensor or isc servo motor is shot.(?)
Later,
Mick
P.S. to techs,
Are there any service manual cd`s available for particular caddy`s? My books are tough to search,decipher, and not much detailed assy/disassy.(for me)
If I were to pretend to be a tech, I`d look into same, or other vacuum issue.
Pressing "Off" and "Warmer" gets you into your dash OBD to pull codes. I`ll guess the techs here will ask for. You probably shouldn`t be messing with mechanical adjustments as the ecm, I believe, controls such as idle speed, unless it or sensor or isc servo motor is shot.(?)
Later,
Mick
P.S. to techs,
Are there any service manual cd`s available for particular caddy`s? My books are tough to search,decipher, and not much detailed assy/disassy.(for me)
Tech Certified Members
Joined: Jun 2007
Posts: 2,701
RE: 1992 4.9L Idle problems
ORIGINAL: 92helldorado
1992 4.9L V8 Eldorado - Pulled the intake box off, noticed lots of black carbon build up inside the throttle body, intake manifold and all over the throttle body blades. Used throttle body cleaner on two different occasions to clear this build up off, and the engine began to run much better, initially. Then the idle became faster and faster. When warming up, the engine idles fine at 1000rpms or so, which is to be expected, but once it hits temperature, it was idling at 1500rpm to 1800rpm. Then adjusted the stop screw, where the throttle linkage actuates the blades, got the idle down to an acceptable 800rpms when warm. Now, it still idles fast, but it appears to be ambient temperature dependent...when its hot outside (80-90* F), it idles fast, but when its cool outside (< 70*), it idles at 800rpms.
Also when it idles high, it trips the check engine light, but no Autozone around here has a OBD1 reader. When it idles low, no CEL. Tried disconnecting the battery to clear the ECM, but problem still the same.
Any ideas whats going on?
1992 4.9L V8 Eldorado - Pulled the intake box off, noticed lots of black carbon build up inside the throttle body, intake manifold and all over the throttle body blades. Used throttle body cleaner on two different occasions to clear this build up off, and the engine began to run much better, initially. Then the idle became faster and faster. When warming up, the engine idles fine at 1000rpms or so, which is to be expected, but once it hits temperature, it was idling at 1500rpm to 1800rpm. Then adjusted the stop screw, where the throttle linkage actuates the blades, got the idle down to an acceptable 800rpms when warm. Now, it still idles fast, but it appears to be ambient temperature dependent...when its hot outside (80-90* F), it idles fast, but when its cool outside (< 70*), it idles at 800rpms.
Also when it idles high, it trips the check engine light, but no Autozone around here has a OBD1 reader. When it idles low, no CEL. Tried disconnecting the battery to clear the ECM, but problem still the same.
Any ideas whats going on?
Adjust the idle screw? tsk .. tsk .. tsk ... bad idea. Idle control valve needs attention .. some can be adjusted, some cannot .. depends on your model year.
Tech Certified Members
Joined: Jun 2007
Posts: 2,701
RE: 1992 4.9L Idle problems
ORIGINAL: toolmaker
I had a `92 eldo that my bro` now has. I had intermittent probs similar to yours with it. I just had intake plenum replaced for similar prob on my 01 etc.
If I were to pretend to be a tech, I`d look into same, or other vacuum issue.
Pressing "Off" and "Warmer" gets you into your dash OBD to pull codes. I`ll guess the techs here will ask for. You probably shouldn`t be messing with mechanical adjustments as the ecm, I believe, controls such as idle speed, unless it or sensor or isc servo motor is shot.(?)
Later,
Mick
P.S. to techs,
Are there any service manual cd`s available for particular caddy`s? My books are tough to search,decipher, and not much detailed assy/disassy.(for me)
I had a `92 eldo that my bro` now has. I had intermittent probs similar to yours with it. I just had intake plenum replaced for similar prob on my 01 etc.
If I were to pretend to be a tech, I`d look into same, or other vacuum issue.
Pressing "Off" and "Warmer" gets you into your dash OBD to pull codes. I`ll guess the techs here will ask for. You probably shouldn`t be messing with mechanical adjustments as the ecm, I believe, controls such as idle speed, unless it or sensor or isc servo motor is shot.(?)
Later,
Mick
P.S. to techs,
Are there any service manual cd`s available for particular caddy`s? My books are tough to search,decipher, and not much detailed assy/disassy.(for me)
TRAINING CD
Thread Starter
Joined: Sep 2008
Posts: 2
RE: 1992 4.9L Idle problems
ORIGINAL: stomper
Carbon is a common problem on many of our cars. I use "SEAFOAM" to take care of that, and it is part of the annual service.
Adjust the idle screw? tsk .. tsk .. tsk ... bad idea. Idle control valve needs attention .. some can be adjusted, some cannot .. depends on your model year.
Carbon is a common problem on many of our cars. I use "SEAFOAM" to take care of that, and it is part of the annual service.
Adjust the idle screw? tsk .. tsk .. tsk ... bad idea. Idle control valve needs attention .. some can be adjusted, some cannot .. depends on your model year.
screw is easily adjusted back so i'm not worried about it, if it won't idle after the ICV is fixed, i'll know where to look.
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