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Electric Fan come on when cold... SOMETIMES?

Old 11-05-2017, 12:21 PM
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luvmy88
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Default Electric Fan come on when cold... SOMETIMES?

I've mentioned this before in other threads and still looking for help.
I have a 88' all stock vette with 96K miles and have been having several issues. One of them is an intermittent issue with my cooling fan which will come on when I turn the key on. Sometimes it doesn't come on right away BUT will soon after the car has started. Just to be clear, this is a totally cold car. If the car is running (still cold) and the fan comes on it willl cause a SES light to come on AND when it does the engine stumbles and SES light flickers.
How does the electric fan influence engine idle???
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Old 11-05-2017, 01:23 PM
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Sounds like your ecm is on its last leg.
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Old 11-05-2017, 01:38 PM
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The fan coming on is a symptom not a cause. The ECM runs the fan when a check engine light is on to keep things cool. Pull the codes and report back to us.
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Old 11-05-2017, 02:37 PM
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Originally Posted by Benny42 View Post
The fan coming on is a symptom not a cause. The ECM runs the fan when a check engine light is on to keep things cool. Pull the codes and report back to us.
The fan coming on and triggering the SES does not produce a code. The SES light comes on and MAY flicker as the engine spudders. Sometimes the fan will quite, the SES light goes out and the engine smooths out.
The last two times I took it out for a test run, I went about 10 miles, car ran fine, then SES light came on. Back at home I check codes and got code 44. (shown in another post)
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Old 11-05-2017, 03:17 PM
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I only read this thread. I know the fan won’t cause a code 44, lean exhaust. Low fuel pressure, one or more bad injectors (likely driver side) plugged filter, failing fuel pump. Fix the root cause and the csr won’t go into limp home mode stumbling running fans.
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Old 11-06-2017, 07:04 AM
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Originally Posted by Benny42 View Post
I only read this thread. I know the fan won’t cause a code 44, lean exhaust. Low fuel pressure, one or more bad injectors (likely driver side) plugged filter, failing fuel pump. Fix the root cause and the csr won’t go into limp home mode stumbling running fans.
Fuel Injectors are new, fuel filter, plugs, wires, coil all new.
Fuel pressure is
44 with key on but not started
39/40 at idle
52/54 at quick acceleration
36/38 when I raise the RPM and hold it there
I have not got a pressure in a highway load condition.
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Old 11-06-2017, 09:25 PM
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If you have the hvac set for defrost the ecm will run the ac compressor to dehumidify the interior of the car.If the ac compressor is engaged you probably will get a radiator fan on.
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Old 11-06-2017, 09:37 PM
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Vacuum leaks can cause a lean condition. Has the intake been off? What shape are all the hoses and plastic vacuum lines The brake booster isn't likely to be it, you would know. New o-rings on the injectors when you swapped them? What is your idle speed? Vacuum leaks can cause it to be higher than normal.
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Old 11-07-2017, 08:51 AM
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Originally Posted by luvmy88 View Post
Fuel Injectors are new, fuel filter, plugs, wires, coil all new.
Fuel pressure is
44 with key on but not started
39/40 at idle
52/54 at quick acceleration
36/38 when I raise the RPM and hold it there
I have not got a pressure in a highway load condition.
All sounds pretty normal. Maybe on the high side or things.
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Old 11-07-2017, 08:53 AM
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Originally Posted by luvmy88 View Post
I've mentioned this before in other threads and still looking for help.
I have a 88' all stock vette with 96K miles and have been having several issues. One of them is an intermittent issue with my cooling fan which will come on when I turn the key on. Sometimes it doesn't come on right away BUT will soon after the car has started. Just to be clear, this is a totally cold car. If the car is running (still cold) and the fan comes on it willl cause a SES light to come on AND when it does the engine stumbles and SES light flickers.
How does the electric fan influence engine idle???
A flickering check engine light is not normal under any circumstances. This is why I think something is wrong with your ecm. You need a scanner and you need to watch the data stream while the problem is occurring.
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Old 11-07-2017, 12:42 PM
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Originally Posted by Benny42 View Post
The fan coming on is a symptom not a cause. The ECM runs the fan when a check engine light is on to keep things cool. Pull the codes and report back to us.
This is correct, the fan comes on when a trouble code is detected. The operation of the fan does not set a trouble code. you mention that the engine stumbles when this happens it seems like a MAF issue but it may not be. Listed below is some information on a code 44.


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Old 11-07-2017, 02:18 PM
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Originally Posted by bjankuski View Post
This is correct, the fan comes on when a trouble code is detected. The operation of the fan does not set a trouble code. you mention that the engine stumbles when this happens it seems like a MAF issue but it may not be. Listed below is some information on a code 44.


Thanks... I've seen this list of checks. I'm unsure of how to do #4 MAF sensor check??? How do you unplug it and not get a code showing it's not working?
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Old 11-07-2017, 03:10 PM
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Originally Posted by Benny42 View Post
Vacuum leaks can cause a lean condition. Has the intake been off? What shape are all the hoses and plastic vacuum lines The brake booster isn't likely to be it, you would know. New o-rings on the injectors when you swapped them? What is your idle speed? Vacuum leaks can cause it to be higher than normal.
I had had everything off from the intake up and replaced all gaskets and seals in the fuel rails and new injectors with o-rings. Vacuum lines all look good and idle is around 700 rpm, but sometimes flickers to 800... it's digital.
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