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Discussion Starter · #1 ·
Hey All,

New here and I need some help. I just bought a 2005 Impala with a 3.4L and I'ts got me stumped. At idle with the a/c off the idle is rough and even worse in gear. If you turn the A/C on it idles and runs smooth. I've replaced the plugs, wires, ignition control module, fuel filter, IAC, TPS, and cleaned the MAF and throttle body with no change. Any ideas?

Thanks,

CC
 

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Well I am not sure what it could be! Have you checked for Leaks or shorts? CHecked your grounds on the battery and the body? Kind of odd really most issues with cars are runs ok until AC on then rough and dies!

NOt sure what you changed the parts you did? Have someone do OBDII testing? Told you to change parts? Do you have any CEL or codes stored? How old is the Catalytic Converter? have you tested your 02 sensors? Tossing parts isn't really going to help unless you know the right part to toss? It could be a Short to ground or Open? There are loads of issues that come up. Not any again have I head of making a car run better with ac running...

Welcome to the Forum, Hope you find some things more useful then what I was able to offer from others that may have had your same symptoms

Edit: I thought about it some, Maybe check your Car voltage? Maybe it is overly high and when you turn on the AC it adds enough load to drop the volts to a safe level for the car???? Again I don't know as I haven't heard of such an issue with our Gen of Impala's
James
 

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Discussion Starter · #3 ·
Thanks for the response. I have checked for vacuum leaks, none found. I haven't checked the grounds at the battery, will do. When I bought the car it had a stumble to it so I decided to do a "tune up" so that's the reason for all the new parts. I did run codes and I has a random misfire codes and a low flow code for the MAF but no CEL The cat is original from what I can tell with 157K on it but seems to have nice flow from the tailpipe and it has plenty of acceleration and power when driving. The O2 sensor are working according to the data stream. I haven't thought about the alternator overcharging, I'll check that! I should clarify a bit, the idle isn't a constant rough, it stumbles...smooth....stumbles....smooth but only a second or so between changes. Anymore ideas?
 

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Well that sounds like Misfire. Have you checked Fuel rail pressure? Injectors? Sounds like you may have a Scanner did you look over fuel trims, At idle and while driving with ac on or off and that would also go with MAF, 02 RPM data as well.. There is something that isn't in sync...

Maybe a leak at the Injector? Intake leak? how does the oil look? How does the Coolant look? any strange smells?

Again not sure kind of strange. Maybe try some Maf testing

James
 
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