Question about 1994 Cadillac DeVille

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Service engine soon comes on and stays on, idles too fast and fast idle solenoid makes noise after turning car off

No readings when checked at part store

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Check the engine computer again for trouble codes, you may find the idle speed solenoid has failed, there is a vac leak, or the throttle plate is sticking open.
You should be able to check a 94 model yourself using the ac control panel on the dash.
The procedure and code list is available online.

Posted on Mar 27, 2015


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1 Answer

Need to know code p0028 is making. Check engine. Light stay on and engine will not idle

code p 0028 refers to intake valve control solenoid circuit , bank 2 ---range performance problem===causes--wiring ---intake valve control solenoid
this solenoid controls the advance / retard of the valve timing for the inlet valve camshaft and will account for the idle problem and the engine light
take it to an accredited service center who has experience on your make of vehicle and have the wiring checked or the solenoid replaced

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When the car in Drive mode, I am getting noise.When I OFF air condition the noise will be coming down. When I switch ON air condition the RPM is not increasing much. Still it is below 1000. How cai I fix...

Release tension on the serpentine accesory belt so you can check the idler bearings, alternator bearing, coolant/water pump and power steering bearing. for looseness and how smoothley they rotate. If a bearing has grease that has dried out it will spin very easily and possibly with noise. Any roughness in the bearing means it should be replaced. That roughness could be the source of your noise.

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As for idle speed of the engine changing when the AC is turned on, there is a solenoid near the location of where the throttle cable connects to the throttle body that should energize when the AC is on, and release when AC is off- this simply pushes the throttle plates open a little bit so engine can idle with the extra load of the AC compressor. Check the wiring on that solenoid to make sure it secure and making good contact as this solenoid also sets idle throttle position on cold engine start too, So a cold engine start with AC on, it will idle above 1000 RPM. A warm engine with AC on should be fine idling at about 800 RPM. About the only thing that you might consider doing is checking for vacuum leaks. A can of carberator/throttle body cleaner should be sprayed on the surfaces where the throttle body bolts to engine, and around any od the vacuum hose connections. Depending on where you are in the world will determine how much anti pollution equipment is installed too- those too can make noise and those vacuum lines should be checked for leakage as well. You will know when a leak is found as the idle will speed up for a moment and smooth out.

When the engine is cold, the noises of anything under the hood/bonnet tend to be louder.

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the engine computer is rasing the idle speed when ever the a/c compressor starts to operate. So it is adding too much air and therefore fuel. The duty cycle of the fast idle solenoid or compensator is off. Check the idle air controls.

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