1973 Bus - Random Engine Idle Hiccup

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dhoch14
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Location: Granada, ES
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1973 Bus - Random Engine Idle Hiccup

Post by dhoch14 » Fri May 22, 2009 10:14 am

While checking the idle the other night I noticed the most-random-what-the-heck-thing that I cannot wrap my brain around.

Symptoms:
While idling, both cold and warm, there is a ever so slight hiccup that comes and goes. My tach typically goes negative or all wacky with a random number. Then poof, the engine and tach are back to normal. It only lasts for about half a second or less. What could cause this?

Any thoughts o'wise IAC folks? :scratch:

Possible replies I see coming from this:
- Faulty Coil --> blue bosch less than 2 years old & 2500 miles.
- Clogged fuel filter --> replaced less than 1700 miles ago.
- Inconsistent fuel pump --> Carter Rotary installed last year and 2000 miles ago.
- Electrical - ?!
- Hubcaps (keeeeeeeeeeeding).
93 VW T4 2.4D Cali

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dingo
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Location: oregon - calif
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Post by dingo » Fri May 22, 2009 11:13 am

Does it happen at random or repeatable time intervals? If so, what are the time intervals? To see if it's a coil or plug, you could hook up your timing light and if there is synchronicity ....
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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satchmo
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Location: Crosby, MN
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Post by satchmo » Fri May 22, 2009 4:16 pm

Check your spark plug wires. Run the engine at night and open the engine hatch and take a look. See any random sparks or arcing? That can cause some trouble. Support the wires so they don't touch anything or each other.

Also check your ground connections everywhere. Random, unexplainable electrical weirdness is often due to bad grounds.

Tim
By three methods we may learn wisdom:
First, by reflection, which is noblest;
second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

vdubyah73
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Post by vdubyah73 » Fri May 22, 2009 7:16 pm

Could be the tach. Disconnect your tach from the coil and see if it goes away.

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