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Old 10-20-2008, 09:24 PM   #1
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Unhappy Poor Fuel Mileage / Loss of Power - Engine Loud During Acceleration

Hello ALL,
I probably have not been on this forum since I first started driving in 2001 (My first car was a 1994 Bonneville SE). Anyways, its great to be back. In April of this year I bought a 2005 Bonneville SLE (50,089 Miles) and am wishing that I didn't, due to all of the nightmare problems that I have been having. I will split up my problems and solutions by paragraph and have a current problem that I am in dier need of help with.
It all started out with an ungodly vibration at all road speeds (non-engine speed related) and i couldn't pin-point exactly what the problem. (Car was aligned / tires rotated and balanced both statically and dynamically 2X, no bent rims - wheels were checked for radial run-out, air pressure up to par and the list goes on - by the way I bought Goodyear Assurance Triple Tread hoping to cure the problem only to find that it was worse so I had them changed under warranty to Michelin MXV4+ - Better, but vibe was still there.) Anyways, after that, myself and an NVH engineer from work fitted my vehicle up with 4 tri-axis accelerometers (1 on each front lower control arm, 1 under drivers seat, 1 on steering column), used road speed input through the hull-effect mag sensor in the driverside front ABS sensor/bearing assembly, and software specifically made by LabView to perform order cuts and order analysis. After all of the testing and data collection we found that there was a 1st order vibration with a high frequency (rim/tire). At school I used a road force balancer and rebalanced all rims/tires and checked for runout only to find that BelleTire didn't properly balance both front rims/tires. After I balanced them and testdrove the car, problem solved.
My next problem happened after I was performing an oil change on the vehicle. I was checking all fluids and changing the PCV valve (just like I do on all oil changes) and noticed that my oil was about a quart low and the Dex-Cool in the overflow resivor was changing from Pink/Orange to a brownish color (almost looked like copper sand appearing on inside of tank). Boy was I PISSED. I performed a pressure test on the radiator overflow tank to find it was leaking internally. So I did some h/w and realized that my lower intake manifold gaskets were probably bad. After 10 hours (includes flushing radiator/cooling system 2x with water + Prestone radiator cleaner) I changed the LIM gaskets, put on a new (reinforced) Dorman UIM Plentum, new fuel injector o-rings (To Rail + To LIM), New TB gasket, New Dorman EGR Stovepipe, New Coolant Bypass Elbows, etc...), then refilled and purged the system with Prestone Any Color Green Coolant. Problem solved and I am no longer having black/cruddy coolant and am not losing oil anymore.
While driving down the e-way (occured before LIM/UIM job) I noticed several times that my transmission would not go into OD and the torque converter clutch would not lockup in any gear (getting crappy mileage). I pulled over and checked out the trans dipstick to notice that there were metal shaving floating in the fluid (I dont have the tools nor time to take off work to fix the trans so I took it in). $2200 later I have a new 4th gear hub set (now Heat Treated - GM should have recalled these things), all new electronics )shift sol., TCC sol., Speed +Position sensors, Pressure sensor, etc...) Car shifts into all gears with no shudders.
**Read below for even more information on all of the **** that I have changed on this car (most for preventative maintaince so I don't have to do this in the snow - no garage)
My problem now is the fact that I get average 370 miles per TANK (I gramma drive the car and this is all E-Way driving), also, in the morning (car engine cold/ambient temp @ 40 F) the engine speed is roughly 1400RPM (it seems like idle should be around 800 or so RPM) after the engine is warm idle goes back down to roughly 800RPM. The other problem I have is it seems that the car has no pickup under acceleration (engine makes loud VVVROOOOOOMMMM noise under acceleration), also if in neutral and engine warm and idle, then you gas gas gas, usually the engine speed should increase when you apply throttle then decrease when let off throttle, etc..., my vehicle when you do this instead of it instantly dropping down when you let off the accelerator, it climbs then very slowly drops down.
I understand that there is a lot of information here, I just want to cover my bases when someone is trying to help me, the dealer doesnt know **** from shinola out here and I dont know who to trust for mechanics.
I think it might be an electronic problem with the mixture (fuel/air ratio running too rich - when i smell the exhaust pipe it seems normal tho) or a problem with the cat (could be making the noise and causing the after cat o2 to read bad values), hoping its not piston rings (low compresson - was thinking about doing compression test but have little time)
IM AT A LOSS, Please help and entertain me with anything that might help me keep my car.

New: {ACDelco Wires/Plugs (0.06" Gap), ACDelco Fuel Filter, AcDelco Air Filter, ACDelco Oil Filter, Mobil 1 5W-30 Oil, GM Transmission Mount, Drained (2x w/water) DexCool - Refilled w/Prestone Any Color Coolant, All new 4T65-E Trans Sensors (TCC / Shift Sol., Speed Sensor, Pressure Sensor, Cleaned Valve Manifold, Drained Trans Fluid (New AMSOil Fluid), ACDelco Trans Filter, 4th Gear Clutch Hub Set (WITH Heat Treat - no thanks to GM), Rebuilt GM Torque Converter (damper spline was toast), Michelin MXV4+ (All around - P235/55R17 @ 30 PSI), Road Force Balanced ALL Rim/Tire Assemblies, Stant Locking Gas Cap, GM LIM Gaskets (Aluminum), Coolant Bypass Elbows (2X), EGR Gasket, Dorman UIM + Gasket + EGR Stovepipe, Fuel Injector O-Rings (To Rail + To LIM), ACDelco PCV Valve, Stant 195 Deg. Thermostat, H3 Foglight Bulb, Wagner Front Ceramic Pads, Front Carquest Rotors, ACDelco Cabin Air Filter}

Cleaned: {MAF Sensor - Using GM Service Manual + CRC MAF Cleaner, Throttle Body - Performed During UIM/LIM Gasket Service with CRC Air Intake Cleaner}
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Old 10-28-2008, 12:23 AM   #2
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It might be the valve or what have you in the trans. Sometimes they run odd my 05 SLE hasn't done that then again it barely has 25K on her and my Impala has acted like that once. I let it sit an evening and drove fine since. Sometimes it is something as simple as a filter. Good luck with your car sorry to hear about your bad luck I have loved mine alot!
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