I have a all stock 93 A4 Trans Am, 103k.

On the way back from the gym, I started to feel like a stutter with the pedal and for a split second I could move the pedal freely before the car starts to go again.

After driving a bit more, I noticed that anything above 1500-1700 rpm like when I hit the gas a bit , it will fall on its *** for a second and I can hear a single knock-like noise from the engine bay before it accelerates again.


Tried playing with the pedal in park and it does the same thing when tapping the gas it will stutter, and I hear a pop noise out of the exhaust but not every time it does it.

Is this a sign of the opti going out or something else?

It has NGK55 plugs in the past 25k, a new waterpump, and wires.

Edit: Also forgot to add, I filled up yesterday, but would bad gas cause this? It isn't knocking/ pinging though.

 

Check the wires first. Make sure they are on snug.

I was on the way back from an all you can eat buffet when mine went south.

Changed
opti
plugs
wires
o2's
coil
ICM
coolant temp sensor

Turned out to be a fuel pump going out. Weird huh?

 

25K miles on a basic copper plug with a wide .050 stock gap to start would likely cause ignition issues.
You can't expect 100K out of plugs unless you go platinum or iridium.

People are way too quick to jump on the anti-opti bandwagon. If you assemble things correctly and don't neglect it it works just fine. They are a distributor though and as such cap and rotor should be considered tuneup items as plugs are and a regular TR55 plug I would not expect to last 25K miles.

 

Did it start happening suddenly or gradually over time?

My vote is ICM

then wires, plugs, opti, coil

 

Thanks for all the advice. I'll have to check all the plugs and wires tomorrow.

It just happened suddenly , it was running perfect before that. (daily driver)

I hope its not the plugs going bad, didn't know they would be only good for 25k considering they were like 50 bucks if I remember correctly lol.

If it were the opti or icm , how big of a pita would it be? And I guess how much would it be for each part ?

 

Update: About two days after the last post, it ended up doing it again and went down to 300 rpms suddenly nearing at a stop sign right before I entered my neighborhood -_- . Ended up having to get it towed to a neighbor's shop.

Ended up being the opti. The old one had the wire/sensor burnt through along with the plastic seal being open slightly. Oh, and it had oil on it from my intake leaking.

Runs much better now that its fixed.

I guess the StL 105+ degree heat maybe messed with it a bit too