84 intermitent running problem

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Sep 4, 2015 | 08:15 PM

gjohnson

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Drifting

Joined: Mar 2008

Posts: 1,809

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From: Denver CO

84 intermitent running problem

After restoring my C-3 I wanted a new affordable vette. I found a nice clean 60k mi 84. Love the car runs great ,execpt every now and then at idle or low rpms it starts to stumble and when you gas it it will pop out of the rear TBI.The only way to get it out of this is to shut it off a restart.WTF? I'm used to my C-3 that is motor/carb w/no smog BS.This thing has so many sensors and sh$t it makes my head spin.The 84 has new fuel pump/sending unit/sock and filter and the tank was cleaned.When it acts up ,it intermitantly flashes the CEL.Previous owner told me of this cond but said he took it in and had it serviced. I have the invoice to prove it. Trouble code was 42. Is it something else? HELP!!Thanks in advance

Sep 4, 2015 | 08:29 PM

antfarmer2

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Joined: Mar 2015

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I would replace the 02 sensor and look for a vacumme leak.

Sep 4, 2015 | 10:22 PM

gjohnson

Thread Starter

Drifting

Joined: Mar 2008

Posts: 1,809

Likes: 441

From: Denver CO

Quote:

Originally Posted by antfarmer2

I would replace the 02 sensor and look for a vacumme leak.

Did search for vacuume leak to no avail. O2 sensor is next. Thanks

Sep 4, 2015 | 10:47 PM

ccrazor

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Joined: Aug 2007

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From: Whitefish Falls Ontario

St. Jude Donor '08-'09

code 42 is the EST (electronic spark timing)..

When I had this problem it ended up being the ECM..

Sep 4, 2015 | 10:56 PM

84Z51J

Racer

Joined: May 2015

Posts: 265

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From: Grand Rapids MI

CEL flashing indicates a misfire, and code 42 with the intake backfire definitely narrows it down to timing. The above diagnostic procedure should lead you to your root cause!