Weird jumping tach [vid]

T

tech9

ABS Expert
I did some work to the truck, new IAC, new distributor, waterpump, egr blockoff, etc.

Now rarely on the highway, or anywhere that you are at a cruising speed.



It actually took me a few days to capture this on my phone, as its very intermittent.
Could it be the distributor? Brand new reman from autozone. I read a few posts that said magnets, or wires, etc.

Its just weird that its jumping up like that, and its making the truck miss, as it jerks slightly when this happens.

You have to be pushing gently on the throttle to get this to happen and constant, if you slowdown, or speedup while its doing it, it stops.

Is it the Syclone ghost of the past?
 
berzerker

berzerker

wookie
Re: Weird jumping tach [vid]my

Re: Weird jumping tach [vid]my

you changed out the dizzy . i would bet your problem lies there . take it back and tell em sorry but no worky . take your money and buy the unit everybody has had luck with from ebay . it's a msd knock off that several people have had luck with . my experience with the vatozone dizzy has been the same as yours .
 
dgoodhue

dgoodhue

BuSTeD 4.3
Re: Weird jumping tach [vid]

Tach flutter means you have an ignition issue somewhere (cap, rotor, plugs, wires, coil, ignition wiring)
 
92TyLA

92TyLA

New member
Re: Weird jumping tach [vid]

same thing happen to me, one of the plugs from the coil came loose. check your coil plugs
 
syclone809

syclone809

Member
Re: Weird jumping tach [vid]

RealFastV6 said:
How could that cause a jumping tach?

The tach gets it's signal straight from the coil- it doesn't share either the ground circuit or the 5V circuit with the TPS sensor.
Click to expand...

Correct. If you notice in his video and description, he's at cruising speed, if he accelerates or decelerates it goes away, if it was the dizzy it would be constant even at idle, not intermittent. Since he's in the throttle, the TPS sensor, which is now getting a voltage reading, has a bad spot where it misses, push the gas and it rises above the bad spot, let off the gas and it goes below the bad spot, therefore its losing voltage and allowing the sensor to drop until it hits a good spot which makes it jump back up suddenly.

I had the same issue, only happened at freeway speeds while cruising, mine had 2 bad spots, I used Tunerpro to diagnose this, changed out the sensor, problem solved
 
RealFastV6

RealFastV6

@jb_and_his_coffee
Re: Weird jumping tach [vid]

syclone809 said:
Correct. If you notice in his video and description, he's at cruising speed, if he accelerates or decelerates it goes away, if it was the dizzy it would be constant even at idle, not intermittent. Since he's in the throttle, the TPS sensor, which is now getting a voltage reading, has a bad spot where it misses, push the gas and it rises above the bad spot, let off the gas and it goes below the bad spot, therefore its losing voltage and allowing the sensor to drop until it hits a good spot which makes it jump back up suddenly.

I had the same issue, only happened at freeway speeds while cruising, mine had 2 bad spots, I used Tunerpro to diagnose this, changed out the sensor, problem solved
Click to expand...

Yeah I strongly disagree. :tup:
 
T

tech9

ABS Expert
Re: Weird jumping tach [vid]

I've been messing with Datamaster a little today, I can't mess with it much because that program pisses me off so much. I can't find any problem with the TPS, its a real GM and its under 500 miles on it, but you never know.

I'm going to try and log when it does it and we will see what is up, but i'm assuming its something to do with that vatozone distributor. Now that I have EGR blockoff, its easier to get the distributor out.
 
Sean Krupa

Sean Krupa

Moderator
Re: Weird jumping tach [vid]

I now have this same exact problem just like the above Video.

I just did a Vortec head/cam swap and have been starting the Ty for the past 2 weeks no issues. Just yesterday the Tach started fluttering.

I just replaced the Control Module, no Fix.

I have new Plugs, Cap/Rotor look good, Wires from last season.

Not sure what else to try besides ordering a new Cap/Rotor and wires and Possibly a new Distributor (even though I just replaced the ICM today).

Thanks,
 
D

Damian

Member
Re: Weird jumping tach [vid]

I just replaced the whole distributor and I found the inside was pretty rusted and the gear was worn down. When it does run, the rpms hold nice and steady.
 
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