2G Tach jumps and car stutters a little

[Vapezilla]

As the title says my tach is jumping at low speeds on my 97 GST and I can feel it the car stutter a little. But the engine doesn't rev, it's just the tach. These are all on low speed and low rpm, I haven't checked yet if the car would do it on high speeds because I'm on break in.

 

[Vapezilla]

My tach is jumping around and sometimes i feel the car stutter. i check the PTU plug and the tab is broken but its there on tight. At low rpm it doesn't do this. But when revving it up or when i do a pull it does this and sometimes if feel it stutter at low speeds and when pulling, the car suddenly just revs and doesn't pull

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[steve]

Are you really redlining a new build with no load on it?

 

[Vapezilla]

Is this timing right? I just parked the car though. So the engine was rebuilt a few weeks ago and i havent driven it really that much. Idk if its just off because i just drove it or the timing is really off.

The reason I'm asking us because I've been experiencing a jumpy tach at around 3k above rpm. That made me think about the PTU and CAS but they are ok. The car ran fine before the rebuild and no jumpy tach. That's why I want to make sure if the timing is off or it's a whole other thing making my tach jump

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[pauleyman]

You have to give us a better pic and without the crank mark that also tells you nothing. It's always relative to crank.

 

[steve]

That's why I want to make sure if the timing is off or it's a whole other thing making my tach jump.

Likely a whole other thing. Is it just the tach or or you seeing engine performance matching it, like missing?

If you still chasing https://www.dsmtuners.com/threads/tach-jumps-and-car-stutters-a-little.545286/ that video worries me, you don't want to rev it like that with no load on a fresh build. Plus it looked like you were hitting the rev limiter.

 

[Vapezilla]

Likely a whole other thing. Is it just the tach or or you seeing engine performance matching it, like missing?

If you still chasing https://www.dsmtuners.com/threads/tach-jumps-and-car-stutters-a-little.545286/ that video worries me, you don't want to rev it like that with no load on a fresh build. Plus it looked like you were hitting the rev limiter.

i'm not redlining it. it's the tach jumping. i think i only revved it upto 4k - 4500 rpm

 

[evil_eagletalon]

Whats the crank timing mark look like?

If your sure its dead tits the timing looks to be off about 1/2 a tooth which is impossible being that the belts don't have half teeth. Now the really plausibility is the 1/2 tooth difference is from possible block/head resurfacing. I would not worry if it was mine unless you are trying to make all the power available then I would recommend the engine to get degrees correctly with cam gears and a degreeing wheel.

 

[Vapezilla]

Is this correct?

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[Vapezilla]

Are you really redlining a new build with no load on it?

What do you mean no load? I just revved it with 10% throttle pressure to see the tach if its spikes or not

Update. I noticed this only happens when the engine is in operating temp but not when cold and and mid temp. Here are the videos I recorded earlier after I drove the car

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Could this be the same as my car situation? https://www.dsmtuners.com/threads/misfire-stutter-stutter-feels-like-spark-blow-out.374891/

 

[Mikealj]

The one where you are actually driving the car looks to me like the transmission is slipping a little...

 

[Vapezilla]

The one where you are actually driving the car looks to me like the transmission is slipping a little...

I doubt that, although yes my transmission is slipping but only on 3rd and 4th gear WOT at around 4500 rpm due which i think is just the master not being adjusted properly. But everything replaceable in the trans like clutch, pressure plate etc was replaced with brand new parts the same time the car was rebuild. Before that the slipping was earlier in the rpm but still just on 3rd and 4th. It's a complete different feeling than a slipping clutch. It only does that when the car is in operating temp but not when its cold. When its cold everything is normal i can rev it fine i can pull fine ( but now a WOT pull obviously ).

 

[DSMPT]

Is this timing right?

The reason I'm asking us because I've been experiencing a jumpy tach at around 3k above rpm.

We can't know if you have the right valve timing unless you show us the crank/piston position. But the valve timing doesn't affect the tachometer to read the engine speed. You should check all wirings and connections first.

 

[Mikealj]

I doubt that, although yes my transmission is slipping but only on 3rd and 4th gear WOT at around 4500 rpm due which i think is just the master not being adjusted properly. But everything replaceable in the trans like clutch, pressure plate etc was replaced with brand new parts the same time the car was rebuild. Before that the slipping was earlier in the rpm but still just on 3rd and 4th. It's a complete different feeling than a slipping clutch. It only does that when the car is in operating temp but not when its cold. When its cold everything is normal i can rev it fine i can pull fine ( but now a WOT pull obviously ).

The cluster in the video is from a car with an automatic transmission. So either I am missing something or there is a strange swap you didn't tell us about.

 

[DSMPT]

What do you mean no load?

He meant that you shouldn't rev a lot a newly built engine without driving.

Update. I noticed this only happens when the engine is in operating temp but not when cold and and mid temp

Does your PTU have the factory mounting/heatsink plate? Maybe you should try another PTU. The PTU often goes crazy when it gets overheated.

 

[Vapezilla]

The cluster in the video is from a car with an automatic transmission. So either I am missing something or there is a strange swap you didn't tell us about.

It's manual swapped but everything worked fine before. I noticed theres a ground not connected and a plug not connected can you tell me what is this for?

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Here's another plug (black) which is unplugged. Im thinking maybe this is a electrical problem

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[Vapezilla]

Update. The ground i was referring to was actually a ground not a positive i though it was because its in the same loom as the postive for the starter. I connected it then my car suddenly starts and shuts off immediatly but my 2g is fine now. Didnt seem to fix the tach issue though

Once my ignition switch arrived and installed i'll update again. My ignition switch is currently not connected to the harness but jumped straight to the battery because of my current ignition switch is faulty. Its my last attempt to fix the tach. If that doesnt fix it then idk what to do anymore