1999 GTS Engine / Driving Issues

[IDM]

Guys these are the symptoms I'm having.

Surging / Bucking while cruising. Feels down on power and exhaust note sounds different while accelerating and slightly different at idle as well.

I am going to pull the plugs and do a compression check as well as change the plugs this week. I am thinking fuel filter/injectors and coils/wires/grounds.

Any other suggestions of items I should check into?

Thanks in advance!

 

[Steve-Indy]

Catalytic converters??

 

[DrumrBoy]

Does it have a tune on it? If so, can you reload it in case it has been slightly corrupted? I run on an AEM that has been tuned on a dyno. If I lose power, the program never seems to come back all the way, so I reload it and all is well.

 

[ViperJohn]

I would also check the IAC and TPS sensors. It's possible that all symptoms have one common source, however, you could have multiple issues. Have throttle bodies ever been syncronized and cleaned? Good luck.

 

[JonB]

MILES MATTER?

Cats? Oxy Sensors?
Plugs, wires?

 

[IDM]

Pinpointed the problem to the coil. Specifically only one of the ports of the coil is bad. #9 is not getting a strong spark and that is causing the misfiring and down on power issue.

So now I will change the coil. Has anyone heard of just one part of the coil outputting weak or no spark but the other parts working fine? Wild...

 

[Dom426h]

Nice that you were able to isolate the problem that quickly. How did you test the coils?

If you have original wires might want to change them out to some more durable ones. I recommend AB's Quality Wires.
http://qualitywires.com/

Also, If you don't already, switch to the updated Champion RC12ECC plugs
RC12LYC is what will show up on the autostores part search.
ECC's are the plug that's are spec'd for the Gen3 motor