Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd - S-10 Forum
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Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

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Old 12-21-2008, 11:50 PM   #1
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Question Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Well... I just got done with a $h!t ton of work to my S10...
-Replaced the gas tank as it was full of rust
-Replaced the fuel pump
-Replaced the fuel filter
-Replaced the Intake fuel lines (nut kit)
-Replaced the CPI spider
-Replaced the cap & rotor
-Replaced the plugs and wires
-New gaskets and seals throughout the motor

Before all of the this it was pissing oil all over the place, surging and running rough at idle. It's not leaking oil any more, but it's still somewhat rough at idle and surges on acceleration,

When it's idling rough.. it's usually not that bad... just annoying. Enough to make the radio antenna dance pretty good. The surging on acceleration is somewhat light... but just as annoying. Both problems seem to be intermittent, but happen parallel to each other.

I've also removed the EGR and cleaned it thoroughly. It's wasn't clogged. I've also tried running it with out the EGR plugged in... no change.

Timing is set at 0 degrees BTDC. All SES codes have been cleared several times.

What should I check next... ??



P.S. Has anybody had any issues with the shift linkage rattling all kinds under acceleration?
Old 12-22-2008, 04:03 AM   #2
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

radio antenna dance=bad ground.
I dont think that's the problem.
Ide look for vacuum leaks.
Old 12-22-2008, 07:50 AM   #3
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

possibly an o2 sensor going bad
Old 12-22-2008, 10:49 AM   #4
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Quote: Originally Posted by Jah
radio antenna dance=bad ground.
I don't think that's the problem.
I'd look for vacuum leaks.
Bad ground? I've replaced all of the vacuum lines and a somewhat sure I connected all right when I put the motor back in. The CPI has a new gasket and a mating surfaces looked good... so I don't think it's leaking from there. Where else would it leak from?


Quote: Originally Posted by sockjock
possibly an o2 sensor going bad
Possible. The SES light will come on from time to time, usually while I'm out on the interstate and the truck has been running for over an hour or 2. It doesn't come on every time it's acting up though...?

Auto Zone Can't read the codes off of mine because it's too old (OBD1) Does anybody know where I can get the trouble codes pulled for free?

Last edited by inderocker; 12-22-2008 at 10:52 AM.
Old 12-22-2008, 11:12 AM   #5
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Ya that sound from your radio is a bad ground some where.
Take starting fluid and spray around if it picks up idle then you have a leak.
Old 12-22-2008, 11:20 AM   #6
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Sorry... I meant a side to side motion... literally dancing.
Old 12-22-2008, 06:21 PM   #7
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Buy yourself a Haynes service manual, it will show how to ground the plug under the dash to give the trouble codes and has the codes listed.
Old 02-25-2009, 11:22 AM   #8
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Update... made a jumper wire, checked for a code and found that the O2 sensor was malfunctioning. I replaced that, but am still having the same issues.

Last edited by inderocker; 02-25-2009 at 11:26 AM.
Old 02-25-2009, 04:19 PM   #9
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Was is saying that it's seeing too rich or too lean?
What does the exhaust and tail pipe look and smell like?
Does it start right up or does it have to turn several rpms before it fires?
Old 02-25-2009, 09:05 PM   #10
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

the surging and rough idle sounds like a vacum leak check around lower intake, TB, hoses, a good rule of thumb is that if you get black crap on your hands after touching the vacum lines they should be replaced .... get a can of carb cleaner or starter fluid and spray around all possible leaks
Old 02-25-2009, 10:11 PM   #11
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

It starts right up and runs good... no indicators of a rich condition. MPG's are not affected. All vacuum hoses have been replaced and no leaks were found at the intake manifold.

Is it possible to have a vacuum lean at the brake booster itself. The booster itself does not work for $h!t so it's next on the list for replacement.
Old 02-25-2009, 10:15 PM   #12
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

well it might not be working because its not getting the right vacuum but it could be leaking there
Old 02-27-2009, 11:06 AM   #13
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Who hit the "report post" button?

Every Moderator just got an email message on this thread.
Old 02-27-2009, 04:36 PM   #14
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Re: Surging & Rough Idle - 1994 S10, 4.3L CPI, AT, 2wd

Quote: Originally Posted by inderocker
...Is it possible to have a vacuum lean at the brake booster itself. The booster itself does not work for $h!t so it's next on the list for replacement.
Usually when the brake boster leaks vacuum internally, the engine will rev up when you brake.

Do yourself a favor and spend ~$15 on a vacuum gauge and fix the problem.
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