2G Tachometer RPM half actual RPM

[Tanro]

My tach is not functioning correctly. I recently replaced my coil packs, and mass airflow. (Coils were weak, and Mass Airflow was non functional) and now my car runs much better. But I am getting poor functionality from the tachometer which I believe is causing some other issues as well.

The car bucks and hesitates at low rpm. And The in-dash tachometer (the stock one) is only reading half what the data stream RPM signal shows (logged with Ecu flash, Matco Maxgo, and Torque (Android) app). The tach will kind of jump around between 0 and 800 rpm at idle. And when reved past 1000 rpm the Tachometer reads only half what the actual engine speed is. If my tachometer reads 2,000RPM the data stream says 4000. If the tach reads 1250, then engine speed is 2,500 RPM in the data stream.

When driving the car will surge, Power will be poor, but then suddenly it will take off like someone kicked it right in the ass, and drive fine until I stop, or come out of boost. The off-boost reponse is still way better than it was before. Car runs way better than before the mass airflow died and before I changed the coils.

Just really need to get this odd issue figured out, and I'd really like to not have to pay well over 100$ for an ignition module from the parts store.

 

[brads]

The tach signal is created from feedback from the power transistor. The data stream calculates engine RPM from the CAS. Reading half RPM on the tach indicates that either 1 of your 2 coil packs isn't firing properly, or 1 of the 2 PTU outputs isn't working properly. It could also be plugs or plug wires.

The tach reading half is a symptom of the poor running and misfiring, not vice versa.

 

[Tanro]

I guess I could try swapping the old coils back and see how it runs. I didn't think of that.

The coils I purchased could be shoddy.

 

[Tanro]

Welll the coils I got were the problem. Put stock coils back in, and all the new problems went away. I got some more coils coming in the morning. See if I can finally get back to banging gears tomorrow.. So tired of driving this damn gas guzzling 6.0 behemoth of a truck everyday.

They were a bit to large to fit the bracket anyways. For anyone searching this, or for future reference. If the coils are about 1/4"-1/2" to wide for your bracket, just send them back.