Can coil or ignition module be bad without throwing codes?

[roswell998]

Can the coil pack or the ignition module be bad, cause poor gas mileage in town but not affect freeway gas mileage and cause surging at low speeds WITHOUT any codes being thrown?

Thanks

 

[justin mccluske]

yes ! but your surging is probly something else thoe .

 

[projectSHO89]

I'll agree with Justin on this one.

Coil failures are rare. Ignition module (DIS) failure is not. Either would be characterized (usually) by loosing two cylinders at a time.

Start by cleaning your MAF sensor and checking for manifold and vacuum leaks.

Few other ideas would include the fuel pressure regulator, uncommanded EGR flow, or a sticky IAC valve.

Steve

 

[SASHO91]

And I'll co-sign Steve... Both times my DIS failed, I got a 212 (or something there-like) code. The car had a MAJOR miss and drivability was not my friend.. To make matters worse, one failed while we (The Texas crew) were out on one of our fun runs. Basically, we were out in the middle of no-where. We were way outside of Austin when it happend(i'm from San Antonio)...
I wasn't very happy on the trip back to the hotel, nor the car.

My point being, you WILL know when you have an ignition problem(plugs/wires aside).

 

[roswell998]

I'll agree with Justin on this one.

Coil failures are rare. Ignition module (DIS) failure is not. Either would be characterized (usually) by loosing two cylinders at a time.

Start by cleaning your MAF sensor and checking for manifold and vacuum leaks.

Few other ideas would include the fuel pressure regulator, uncommanded EGR flow, or a sticky IAC valve.

Steve

This thing is driving me nuts!

In answer to above questions/comments:

New OEM MAF
Fuel pressure...41 static/30 idle/40-41 with vacuum line disconnected
New IAC
New DPFE
New intake manifold gaskets
Can't find any vacuum leaks (but maybe I'm missing something)
Cylinder balance test passes

Ahhhhhhhhh............Massive headache........!!!!!!!!!!!!!