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trothle pos sensor and mixture control solenoid

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Old Apr 15, 2008 | 01:00 PM
  #1  
andresinibus's Avatar
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From: Mesa AZ
Car: 85 Z28 W/T-Tops
Engine: 383 crate engine edel carb n headrs
Transmission: ex700R4/NOW T5
Axle/Gears: 3.08 std
trothle pos sensor and mixture control solenoid

Hi guys does any of you know how to test (if possible) any of this two parts its off an 83 quadrajet # 17083204 thanks
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Old Apr 15, 2008 | 08:01 PM
  #2  
Damon's Avatar
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From: Philly, PA
Re: trothle pos sensor and mixture control solenoid

MC solenoid you can bench test very easily with no special tools. I do 2 tests on them:

1. At room temperature (not hot, not cold) unplug it and check for resistance between the 2 poles of the MC solenoid. Spec is about 20 Ohms. If it's significantly higher or lower, it's shot, regardless of whether it apparently works or not.

2. The solenoid is just an electro-magnet that operates on a full 12V of battery voltage (cycled by the ECM when the engine is running). You can run some temporary jumper wires over to it from the battery to do a simple field test. Every time you complete the circuit (polarity does not matter) you should hear a click (pulling the rods down). Every time you break the circuit again you should hear another click (the rods jumping back up). You should be able to click it up and down as fast as your little fingers can make and break the connection- it moves those rods REAL fast.

TPS is a little different, and the easiest way is to hook up a scan tool and note the TPS voltage the ECM is reporting at different throttle positions. Should be about .5V at curb idle and about 4.5V at WOT (although they often don't get much over 4V in many cases, through no fault of the TPS itself).

You can also field-test it with a volt meter but it requires rigging up some (3) special jumper wires to go between the TPS and it's plug so you can tap into it and read voltage while it's actually hooked up and talking to the ECM.

Last edited by Damon; Apr 15, 2008 at 08:04 PM.
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Old Apr 16, 2008 | 12:28 AM
  #3  
andresinibus's Avatar
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Joined: Feb 2008
Posts: 184
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From: Mesa AZ
Car: 85 Z28 W/T-Tops
Engine: 383 crate engine edel carb n headrs
Transmission: ex700R4/NOW T5
Axle/Gears: 3.08 std
Re: trothle pos sensor and mixture control solenoid

thanks for replaying Damon i will do those tests i was also wondering if its normal that every time i turn the key to the on position the MC does that clicking for like a minute or so then it stops thanks for the help
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Old Apr 16, 2008 | 02:52 AM
  #4  
dirtywhiteZ28's Avatar
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Joined: Jan 2008
Posts: 293
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From: Houston, Texas
Car: 84' Z28-White/T-Tops
Engine: H code LG4 305
Transmission: TH700R4
Axle/Gears: Stock 3.23
Re: trothle pos sensor and mixture control solenoid

The clicking is the M/C soleniod. That's normal, mine usually stops clicking after about 30 secs, but I've seen a lot of variation in time on this between cars.
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Old Apr 16, 2008 | 06:06 AM
  #5  
Damon's Avatar
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From: Philly, PA
Re: trothle pos sensor and mixture control solenoid

Yep, that's totally normal. Not all GM cars with the CC-QJet do it at key-on (most notably Olds and Buicks) but almost all Chevys do and definitely Camaros and Firebirds.
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Old Apr 16, 2008 | 03:51 PM
  #6  
andresinibus's Avatar
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Joined: Feb 2008
Posts: 184
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From: Mesa AZ
Car: 85 Z28 W/T-Tops
Engine: 383 crate engine edel carb n headrs
Transmission: ex700R4/NOW T5
Axle/Gears: 3.08 std
Re: trothle pos sensor and mixture control solenoid

ok thats a relief i thought my MC was fried much better
thanks guys
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