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Primary cooling fan issue on 3.4 Lumina, also erratic idle


pose_Z34

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I have a couple issues with my Z34, first the primary fan will not switch on. I've tested the motor and relays by jumping the ALDL, and they're perfectly fine. Thinking maybe coolant temp sensor, or other issue. Also, it wouldn't kick on when I hit Max on my AC with the car in the "ON" position. Would love some insight.

 

Also, having an issue with cold weather erratic idle. I don't think it's a gasket issue, since it goes from 1500-2000 when cold. I already have installed an IAC unit, but went ahead and ordered a GM unit, as well as a GM MAP sensor. Am I on the right track?

 

Any help would be appreciated.

 

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first. check the fans to make sure the ecm/pcm trigger them. do that with a paperclip at the ALDL... they cycle on when you check the engine light.

 

do they turn on?

 

 

next unplug the temp sensor. turn the key to run. what happens? do the fans turn on?

 

 

 

if yes and yes... get a new temp sensor.

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As far as I know the gaskets are good. That crossed my mind since it idles high when it's cold outside, then surges, then idles okay. Of course a gasket could expand in the heat and seal up when warmed up.

 

My trouble code is 35 which is idle issue or IAC issue.

 

Last time this happened, I replaced the IAC motor and it fixed the problem. I found a new AC Delco unit on ebay for dirt cheap, so I thought I'd start there, and go ahead and change the MAP sensor since it looks rough. I figured the gaskets are a worst case scenario.

 

I'll plan on looking for a good set of uppers and lowers with the sealer already on therm for my best bet. May as well do it all if I do it.

 

I just don't want to throw parts at it and it not fix the issue.

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You can test vacuum and leaky gaskets with some carb cleaner. Spray the lines and gasket mating areas while the car is running. A fluctuation in idle will indicate a leak.

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New vacuum hoses helped a ton on the idle, just need to replace the one under the plenum that goes to the fuel pressure regulator. Figure I'll hit that once my temp. sensor arrives this week.

 

Idle is much better overall, right around 800 rpm in neutral when warmed up. A little higher when cold, probably due to the afore mentioned regulator.

 

 

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