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Discussion Starter #1
What would cause your intial timing to jump around all over the place? it reads 34 then 8 then 0 then 20 real fast, its jumping all over the place at idle and low rpm. and it also has misfires at these same rpms even after i did a full tune up. its a 95 S10 pickup truck...
 

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Bad timing chain or gears is the first thing that comes to mind. Possibly a bad distributor. Probably need to move this to the drive train thread.
 

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Try changing your advance springs first. Might be worn out, cheapest thing to do, then work up from there....


T,
X2:yes:......
 

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Discussion Starter #6
i did notice after i did the full tune up that the problem was amplified. just thought id bring that up since it may give anyone an idea. i will check the distributor and vacuum lines now. also how do i check the timing chain if its bad or loose? the motor has only 20K miles on it though... any help is greatly appreciated.....
 

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Was the vacuum advance disconnected?
 

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I know on my TPI car there was a wire going to the distributor that had to be disconnected to time the engine, I bet yours is like this as well. I beleive it was a brown or dark tan wire that controlled the computer controlled advance in the distributor.
 

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Discussion Starter #11
I know on my TPI car there was a wire going to the distributor that had to be disconnected to time the engine, I bet yours is like this as well. I beleive it was a brown or dark tan wire that controlled the computer controlled advance in the distributor.
would that also cause a misfire with a very slight rough idle?
 

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A misfire and a rough idle could be caused by a number of things. Start simple and double check the firing order. Make sure all the wires are firmly in place on the cap and plugs. Make sure you don't have a burnt plug wire. The tgiming jumping around if the dizzy isn't getting the right signal can cause this as well.
 

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Dwell variation can change timimg.

One main cause of dwell variation is worn dist shaft bushings or dist shaft end play bushings......


Does the rotor shaft pull up and down alot?
The helical gear design will change timing with up and down movement.

Does the rotor shaft move side to side alot?
This will also give your timing variations.

Remember!

Dwell effects timing but timing will not effect dwell!
 

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its a 95 S10 pickup truck...
If it is still in the original vehicle, there will be a decal under the hood with the plug gap, timing specs, & specific instructions on how to set the timing on that engine.
 

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Discussion Starter #15
i got 2 manufacture specific codes on my friends auto x-ray scanner. they are P1100 and P700 anyone know what they are? the scanner cant tell me because they are maufacture specific codes and the scanner will only read under a generic setting because its a 95 S10 4x4 vortec (W) vin vehicle... anyone know? thanks so much
 

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What would cause your intial timing to jump around all over the place? it reads 34 then 8 then 0 then 20 real fast, its jumping all over the place at idle and low rpm. and it also has misfires at these same rpms even after i did a full tune up. its a 95 S10 pickup truck...
had the same problem on a 4.3 and it turned out to be a worn distributor gear believe it or not. but it could also be lots of other things.
 

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P1100 MAF Intermittent

P1100 Manifold Absolute Pressure (MAP) Sensor Malfunction (Open/Short)

P0700 Transmission Control System Malfunction

I found these with a Google search. Dont know if they're correct or not.

When did it start having this problem... was there anything that preceeded it?
 

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Discussion Starter #18
had the same problem on a 4.3 and it turned out to be a worn distributor gear believe it or not. but it could also be lots of other things.
thats what im starting to think it is too. did your distributor rotor have play in it before you pulled the distributor out of the engine to see the gear was worn out? did you also have misfires? and was your timing in the negative area on the scanner jumping around when you scanned it? if you did hook it up to a scanner that is? thanks so much
 

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Discussion Starter #19
P1100 MAF Intermittent

P1100 Manifold Absolute Pressure (MAP) Sensor Malfunction (Open/Short)

P0700 Transmission Control System Malfunction

I found these with a Google search. Dont know if they're correct or not.

When did it start having this problem... was there anything that preceeded it?
hi, can you send me the link on where you found these codes? because i would only find everything but the P1100 code....
the problem has been there for some time now, but recently getting worse as time goes by....the motor always ran rough, since not to long ago since the dealer put a new long block in it 3 years ago....
 

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The timing is PC controlled.

It is not unusual to see the timing greatly fluctuate on a odd fire V6 Vortec System.

The timing fluctuates to millisecond conditions and on this odd fire engine.
It moves around for smooth engine operation.

There is no mechanical or vacuum advance.

Al
 
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