PontiacBonnevilleClub.com

when in drive, the bonne will stumble and just sound unhealthy. but its only at 1/4 inch of throttle, like when i'm creeping through a parking lot at 5 to 10 km/h. great torque, great takeoff, decent gas mileage, no rpm fluctuation in OD even under load, this has me baffled. I recently got a loud muffler put on, so now i can hear the sound of it, and it sounds horrible like that. please help.

Dead spot in the TPS? Any codes?

Go back through this list, and if you can't remember when you replaced it, replace it. That will at least eliminate things like a bad plug wire, etc.

• 1987-2005 Bonneville / Buick 3800 Maintenance List
  
  Run Seafoam through gasoline and intake every 5,000 miles. One pint of Seafoam in a half tank of fuel is a good mix. The intake is optional, but recommended.
  
  Grease: Ball Joints, Tie Rods Every 8-10k ( Green Grease recommended)
  Air Filter Every 15k (Amsoil EaA, Purolator PureONE)
  PCV Valve Every 30k
  MAF Sensor Element Cleaning/TB Cleaning Every 50k viewtopic.php?f=48&t=1661
  Fuel Filter Every 15-25k (Purolator, AC Delco, WIX)
  Spark Plugs Every 30-50k (NGK TR55 or Autolite 605) (Never Bosch)
  Ignition Wires Every 30-50k (Napa Belden, AC Delco, Autolite Pro, NGK) (Never Taylor or Bosch)
  Oil & Filter Every 5-6k or Every 6 months (Mobil1 or Amsoil)(Mobil1, Purolator PureONE, Amsoil EaO or WIX) (Never Fram) viewtopic.php?f=45&t=214
  *Conventional Oil Every 3k/3 months(Pennzoil with a WIX (Napa), Delco or Purolator filter)
  Transmission Flush or Pan Drop Every 15-20k (Always make sure filter is changed when flushed) http://www.pontiacbonnevilleclub.com/fo ... 45&t=10193
  Cooling System Flush Every 25-50k or 3-5 Years (Peak or Prestone Green Coolant Only) (Never Dexcool)
  Oxygen Sensor Every 80-100k (30k for non-heated) (AC Delco or Denso) (Absolutely never Bosch) viewtopic.php?f=48&t=794
  Accessory Belt Inspect every 15k, replace every 100k, or as needed
  Cabin Air Filter Inspect and Replace every 15k, or as needed in dusty conditions. (Note: 00+ Only)
  Evap Core Cleaning Whenever Needed (Note: 99 and older only) viewtopic.php?f=45&t=2432
  
  *Special Considerations*
  All 3800s, LG3, LN3, L27, L36, L26, L67 & L32, especially important on vehicles factory installed with orange Havoline Dexcool Antifreeze/Coolant: http://www.dex-cool.net/
  Lower Intake Manifold Gasket Replacement, every 80-100k (ignorance of this can allow coolant to enter your engine oil, this happening can cause irreversible lower engine damage, requiring replacement of subject engine)
  
  Series II, Naturally Aspirated, RPO:L36:
  Upper Intake Manifold Plenum Replacement, Every 80-100k (ignorance of this can allow coolant to enter your intake manifold, possible damage to occur can be hydrolock, irreversible damage to emissions devices, misfires, etc. Most times, engine replacement is required if ignored long enough.) viewtopic.php?f=53&t=1061
  
  Series I, II, III RPO Code L67 & L32:
  Change Supercharger Oil; Every 30-50k. (Intense Racing or GM Dealer) viewtopic.php?f=56&t=1690
  Supercharger Belt; Inspect Every 15k, Replace Every 100k or as needed.

9/7/10 by 00Beast

Sounds ignition related to me. Or maybe a plugging fuel filter. When something similar happened to me, it was an ignition coil. There's a test procedure in Techinfo.

Hence why I said check the list. If it is a fuel filter or wire, he'll know once he does all that.

Always take care of maybe-ignored regular maintenance items first, as 00Beast said. I have always found this to be a great "trouble-shooting" starting point. You need to "base-line" your vehicle before starting to replace parts at random.

Exactly renchjeep. Lots of those things are overlooked during "maintenance" and cause big issues if/when they go bad. First thing I did when I had my misfire issue was replace plugs and wires. That didn't fix it, but then I knew it was something larger. If I had replaced coils first and discovered I had a bad wire, I would not have been happy.

ok, i have checked the coils, because thats a freebie. waiting on some cash flow till i can replace the wires and plugs.

Just be aware that a intermittent coil can test fine. That's what happened with my misfire.

I changed out the coils one at a time with some used replacements i had kicking around. never changed anything, after each coil change i'd go for a drive and have it do the same miss under light throttle. so i bought new plug wires, and it seemed to make the whole car a little better, but I'm still experiencing the miss/hesitation. Where do I look next? It feels like a fuel problem, and I do have plans to change the fuel filter, but what else could cause the symptoms at only light throttle? wot is fine.