Changed fuel filter no won't idle

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Oct 16, 2011 | 11:19 PM

Mtn Billy

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From: Colorado

Changed fuel filter no won't idle

I have a '85 C4 with 54K miles that sat for about four years. when I purchased her the only things that needed to be done were A/C charge. Repair the vacuum lines under the dash and service. My problem started after I changed the fuel filter the car won't idle when hot. Idles fine when the engine is cold. I didn't get much help from the FSM.

Anyone have any ideas?

Thanks

Oct 17, 2011 | 01:37 AM

oldalaskaman

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put the old filter back on

Oct 17, 2011 | 10:55 AM

Mtn Billy

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From: Colorado

Quote:

Originally Posted by oldalaskaman

put the old filter back on

I should have added that it was loosing power. That's the reason for the change.

Oct 17, 2011 | 12:34 PM

oldalaskaman

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you may have got a bad filter

Oct 17, 2011 | 02:38 PM

Joe C

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gotta ask - is it installed in the right direction? remember, ya got this thing called murphy's law!

Last edited by Joe C; Oct 17, 2011 at 03:08 PM.

Oct 17, 2011 | 03:54 PM

Mtn Billy

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From: Colorado

Quote:

Originally Posted by Joe C

gotta ask - is it installed in the right direction? remember, ya got this thing called murphy's law!

Yup. Been there done that. Now I mark the flow..

Oct 17, 2011 | 05:04 PM

Joe C

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Quote:

Originally Posted by Mtn Billy

Yup. Been there done that. Now I mark the flow..

, OK now i've got to ask, what kind of filter? is it a GM/OEM filter, or some "made in china POS"? since your problem popped up with the filter change, it's gotta be something related to the filter.

Oct 17, 2011 | 05:57 PM

BADDUCK

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From: One day you're a Comet...the next day you're dust... Arkansas

If it idles fine cold but not hot I doubt it has anything to do with the fuel filter. Check your injectors resistance hot and cold.

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Oct 18, 2011 | 02:28 AM

Cliff Harris

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From: Anaheim CA

Bad idle when hot (in closed loop mode) could be a bad O2 sensor.

Oct 18, 2011 | 10:00 PM

#10

gmboileau

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From: Toronto Ontario

Check the fuel pressure. A failing pump will not deliver enough fuel thus the loss in power..

Oct 18, 2011 | 10:19 PM

#11

Mtn Billy

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From: Colorado

Quote:

Originally Posted by Cliff Harris

Bad idle when hot (in closed loop mode) could be a bad O2 sensor.

I was told it could be the O2 sensor, and possible the ERG. Anything do do with fuel pressure/delivery is low on the list as it runs great and has lots of high RPM power. I was also advised the it could be the IAC.

I need to keep this KISS to get out the bottom of this pit.

Thanks to all
Bill

Oct 18, 2011 | 11:22 PM

#12

John A. Marker

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From: Dublin CA

Just have to ask...any codes?

Oct 19, 2011 | 02:37 AM

#13

navy_vette

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From: Naples Campania

Quote:

Originally Posted by Mtn Billy

O2 sensor is definately possible. They are fairly cheap and easy to install. I would test them first, but they could just be gunked up. That would be the first thing I would replace.

This is just a diagram of a basic EGR valve system. It's not exactly what is in our cars, but it's pretty close. The inlet for the exhaust gas is actually smaller on ours. They get easily clogged or the valve gets stuck shut or open. It's a bit of a PITA to change, but it's a possibility.