So not sure if it's stumbling or minor wheel hop, but it only occurs between 40 and 50 mph.

Here's how it happens...completely repeatable.

- Only occurs when it's hot outside (evenings going home from work).
- If I cruise at 40ish WITHOUT foot on the gas pedal, and then press on the gas, it hestitates/stumbles a little before getting moving.
- Won't do it under 40 mph or over 53ish mph. Just that window.
- Feels fine if I accelerate through that window...say 20 to 65 mph. Only if cruising in that window.

Again, it's completely repeatable...I can do this all day around this speed...which unfortunately is the normal speed limit for the street roads around here.

It's not the fuel pump, because I just replaced that this past weekend...yeah, that sucked...another story.

Being that it only occurs when it's hot, I figure it's electrical. But why would it be at only certain speeds...seems like if it's the coil or ICM, it should do it at any speed, right?

Anybody seen speed related stumbling/hesitation?

 

Going through the same problem...But it's not heat related, it comes and gos and only does it when I step lightly on the pedal between them speeds, if I romp the pedal down, she'll take off like nuts

 

Hmm...how long have you had that issue. I'm guessing it's heat related for me, because it happens in the evenings when it's hotter. i don't see it in the mornings when I go to work.

Same speed range, huh? Interesting. Let me know if you ever find out what it is. Sounds exactly like mine...only when you barely step on the gas does it happen.

I've changed my opti 20K miles ago, new fuel pump last week...I'm thinking maybe coil or ICM.

What was your last mod, before you noticed this? Mine was a rebuilt tranny with slightly higher stall (2200), shift kit, and rearend gears.

 

I was going through the same thing and finally eliminated it. Here is what I did:
1. changed throttle bodies (mine was leaking air through the top cover.
2. changed injectors
3. changed plugs and wires (had borg-warner wires and acdelco plats, now acdelco wires and champion copper plugs)
4. new mass air flow
5. new alternator
6. new msd coil
7. repaired opti harness (insulation was cracked, fixed it and sealed it with silicone to keep moisture out of pigtail)

I dont know which one fixed it, but it was probably the mass air flow and the opti harness.

 

I have a stumble like you are mentioning, but mine is not heat related.

I have replaced..

ICM
Plugs
O2 sensors
Coil
injectors

cleaned the mass air


Nothing seems to resolve it.

I also get a vibration.. 2000-3000 rom in 4th gear is where i really feel it.

Full throttle, or mid throttle passing thru that range is not a big deal.

Full throttle I have full power.

I dont know what it could be.

Adam