Resolved 2G tach is bouncing all over

[goldeninja20]

Yesterday i got the car running amazing after a fresh rebuild. today i went to take the car for another spin. The rpms are bouncing all over the place and the car is bucking. I checked all the cas wiring and it is fine. I have a 6 bolt swap so i have no crank sensor just cam sensor.

 

[SlushBoXRacer]

Check the Transistor pack for corrosion in the connector.

 

[Bolo'sTalonTsi]

Fuel flow issue?

 

[Diamond Star Werks]

CAS is bad. RPM bouncing means where it gets, it signal (CAS) the sensor is bad. if all wiring is good then sensor itself bad.

 

[GRAVEDIGGER]

It has to be ignition related. A fuel problem won't make the tach jump around.

How's the battery and alternator?
What is the voltage with the engine running?

If that checks out ok I would be looking at the power transistor/ignitor too.

 

[ramsack]

A bad CAS would make the car run like ass. The tachometer gets its signal from the ignition system (power transistor, or for 1990 a special gate circuit/chip), not the CAS.

 

[T is for TURBO]

Are you getting any codes?
Are you doing anything to prevent the random misfire that is a problem with 2gs 6bolt swaps using only a 1g cam sensor?

 

[josh408]

Like everyone is saying, check the power transistor. That would be easy, then check the CAS. Not too hard

 

[dsmgabe]

If you are still on the factory ecm you need to check the speed-o gear sensor
on the transmission. If the plug comes off the sensor the car can do this.

 

[ramsack]

No. Just...no.

 

[BurrowZ]

If you haven't experienced a "bouncing" tach and stutter/buck/jerk at the same time, do not reply.

I have this problem about once a week because my plug to my PTU doesn't clamp since the locking tab broke right off. It will wiggle loose and my tach will dip and drop and car will stutter badly.

As stated, check PTU and your CAS. I say CAS too because it is an input to the ECU to tell your car when to fire the plugs and injectors. You don't have a CPS so those two are pretty much your only possible problems. Check for corrosion in the plugs too.

It is somewhat possible your ECU could be on it's way out but pretty unlikely. Check the above and get back to us.

 

[goldeninja20]

I have this problem about once a week because my plug to my PTU doesn't clamp since the locking tab broke right off. It will wiggle loose and my tach will dip and drop and car will stutter badly.

This was exactly the problem. The locking tab broke and loosened the plug on the ignition transister. Thanks for the first quick reply. I had the problem resolved 10 mimutes after I posted.

THANK YOU DSMTUNERS.

 

[Diamond Star Werks]

If you haven't experienced a "bouncing" tach and stutter/buck/jerk at the same time, do not reply.

I have actually. with my own car and customers. op glad its fixed!