This topic contains 4 replies, has 2 voices, and was last updated by 
Jerry Quezada 5 days, 1 hour ago.
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Lately I have been experiencing rough idle on my SUV. This started back in Dec where it would rough idle during cold start but then level out and work like a charm. This past week, the idling was progressing on affecting the car drivability. The rough idles starts at times during the cold start in the AM then goes away, however on a stop light the car would idle fine, then start to rough idle – thermostat 1/4 open according to the gauge. It would drive fine in the highway (I drive about 24 miles total round trip to work). One the return home I experience the car idling rough more frequent during stop lights, then work fine when I feed it some gas, the begin to rough idle when stopped. I cleaned the throttle body and the car purred fine, ran great for a day, now last night when parking the car – it rough idle and shut off on me. I plug the OBD-2 and no check engine light. However I did a live data feed while idling and it marked the RPM 450, if I am not mistaken it need to be at 800. Can it be the EGR valve that is going bad? I can hear the hissing of air when driving and idle. Other than that not sure what else can cause as all hoses are connected and no leakage. Also I ordered a new fuel filter, feel free to add your 2 cents on what else I am overlooking.
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Have you checked for vacuum leaks? That hissing noise you mentioned can also be a vacuum leak. Also, I would suspect the idle air control valve is getting an internal block, sticking intermittently or going bad.
I changed the EGR valve, the hissing was coming from a missing hose that connects from the EGR valve to the EGR control-BPT valve. I did put a temporarily nut and it idle fine – for a short period of time. Now it is rough idling again, I order the missing hose that connect the EGR valve to the EGR control, should be coming in next week. Some of my friend suspect it is the spark plugs or distributor cap – however no check engine light is active.
Does your engine have mild misfire or power loss on acceleration?
On the highway the acceleration does not respond as it should. However When I drove it, everything was fine until I got to work and it began to rough idle. I changed the spark plugs (old one were full of carbon 5/6 of them) and changed the O2 sensors all 4 (Bosch sensors). I plugged the OBD-2 and during idle it goes from 800 RPM down to 350-480 rpm. My neighbor might suspect it is the distributor cap causing the issue.
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