Hi everyone,

I’m a new member here looking for some help. I recently purchased a 2005 Bonneville GXP with 190k on it. I’ve always been a Pontiac fan and have owned 2 Grand Prix’s and a GTO. So I found a deal I couldn’t pass up. The car itself is extremely clean in and out. The interior of the car looks like new and everything works. The exterior is the same, except for the headlights, small rust around the gas cap and a missing fog light. I have heard how the 4.6 FWD have their problems, but what made me buy this car was the very good price and the owner had just recently replaced all tires, brakes, rotors, (newer battery) and a rebuilt Trans. It’s too good a car to just let rot.

So when I purchased the car, it did not run, the owner just said his daughter was driving it and it died and needs a new motor. There are no visual sings of damage to the motor. I towed it to my house, charged the battery and tried to start it. It cranks over for some time and then starts but will not stay running on its own. You have to keep you foot in it. But once you’re above 2-3k RPM it runs like it should. It smoked a little at first but only for 2 minutes now no smoke coming out of the tailpipes. I have a 07 DTS that has the same motor and it sounds exactly the same at the higher rpm range, no crazy noises or clunks. I have a cheap code reader and read codes: p0300, 0410, 0420, 0455, 0442, 0449, 0160, and 0385. These codes, (from what I’ve found) are all emissions related codes except 0385.

I started with the basics oils clean, coolant seems to be OEM dex-cool, check the plugs, and they were bad. Changed them out and car still does the same thing. Not sure if the coils are bad, but cant see all 8 being bad. So thinking possibly a clogged cat, drilled a 7/8 hole before the catalytic converter, and put 3 gallons of fresh gas in it. Started the car and same thing, won’t idle but runs great at 3k and up. Drove it maybe a ¼ mile around. The car runs and drives just fine when you’re on the gas, I had my foot in it while holding the brake. Now, after tinkering with it, I doubt the motor is “bad” I think its one or a combination of a few things, so looking for some insight from you guys.

Bad ignition coils?

Bad Crankshaft Position Sensor?

Water In fuel? Kind of eliminated that because it runs good at higher rpms? Mine had water in the spare tire area. I talked to a guy who claimed his Bonneville had a leak in the fender well passenger side and water got in and into the fuel tank over time.

Bad Battery, read somewhere that the coils are pretty sensitive and need good battery?

Any help would be greatly appreciated.

Thanks

How was the coolant level?

P0300 is not good. That is random/multiple cylinder misfire. Same code that pops up when the car is eating coolant. Not saying that is the problem for certain but they are KNOWN for headgasket issues.


Could do a leak down test to show for sure if that is the problem or not. Any bubbles in radiator/coolant overflow will indicate a problem.

_________________
Clay
1997.2 40th SLE-138k
1968 Bonneville 400ci w/TH-400-40k
1999 GMC Suburban SLT-191k
2005 Escalade 253k-GINA

190k on a GXP, well beyond the expected life. How much did you pay for it?

_________________
Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

Way too many things it could be to be honest.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

I'd like to see some photo's

_________________
Member #3848
2002 Black Bonneville SE Sold But Not Forgotten
2002 White Bonneville SSEi Project car

The coolant overflow tank is between the full and add, so I don't think its loosing coolant. But if the head gaskets were bad, would that prevent it from starting? And when it was running in the higher rpm range like I was saying it would be smoking white?

When I bought it, I knew 190k was pushing it, but still think the motors just needs some tlc.

Not unless it's hydrolocked. But you'd know that easily if it were.

My guess is that it's just something electronic like MAF, TPS, or another sensor, harness, or controller.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

Ditto. The sky isn't falling just because it's a Northstar with 190k... sensor/electronic issues in this case would be NO different from any 3800 powered Bonneville. Yes the timing and valvetrain hardware is more complicated as a DOHC, but the basic sensor setup isn't that far off.

I'd start with the P0385 and suspect the crank sensor. There should be two crank sensors, A and B. B (associated with the P0385) is the lower one. 2000-2003 models years often had sensors go bad, but 2005 may not be immune. Have a look at these threads:

http://www.cadillacforums.com/forums/ca ... ement.html
http://www.cadillacforums.com/forums/no ... ition.html
http://www.cadillacforum.com/forum/cadi ... 0-dts-820/
http://www.cadillacforums.com/forums/no ... ement.html

If replacing, the crank sensor will also need to be relearned. This is easiest using a Tech 2 scanner, but (I haven't verified this) you may be able to do it with this procedure.

_________________

Jerry /// Past: 95 SSEi (June 2010 COTM) -- 04 GXP (July 2011 COTM)
91 Honda Civic Wagon DX 2WD (fuelly) -- 208,000km -- 92hp -- Autocross Warrior
09 Lexus LS460 AWD -- 94,000km -- Daily Driver
09 White Hot G8 GT -- 155,000km (fuelly) -- LS3 Cam -- GM LS3 CNC Ported Heads -- Kooks 1 3/4" Long Tube Headers -- Solo Catback Midsection -- Hooker Maxflow Mufflers -- Pat G Tune -- Rotofab Intake -- Tein S-Tech Springs -- GXP FE3 Dampers -- BMR Subframe Cradle Inserts -- BMR Subframe Connectors -- Forgestar F14 Gold 18x9 +40 -- Michelin Pilot Super Sport 245/45/18 -- Maverick Man Carbon Fiber Spoiler

Thanks for the links repinS. I un-hooked the MAF to see if it would change things and it didn't. I'm also suspecting a dirty throttle body. As far a the crank position sensor goes, I'm leaning towards that being the main issue. My question is, if the sensor was bad, would that only effect the starting and idle? It runs fine at 3k and above.

I also need to do the battery ground issue with these cars. My DTS had the problem, just wouldn't start one day. Pulled the chassis ground wire and sanded it to bare metal and haven't had a problem since.

You probably need to clean the MAF thermistors too. Take it out, then shoot them with some MAF cleaner that you can get at any auto parts store. Suitable spray alternatives are an electronics contact cleaner and if worse comes to worse, brake cleaner. But some brake cleaners (like the cheap *shoot* at AAP... sorry Will), leaves a residue. So I would try to use that as ONLY a last resort.

Grounds can be bad in any car.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

I unplugged the MAF with no change. I then pulled the air box to get to the throttle body. Cleaned the throttle body with cleaner and still nothing. I then sprayed starting fluid into the intake and it wouldn't fire. Pulled the ignition coil with the plug and grounded it and Its getting spark. So the engine is getting spark and will not fire with starting fluid. But after cranking for a while it fired with and ran with my foot to the floor only producing 2k rpm. So still not sure whats going on.

Fuel pump or other fuel blockage, or lack of fuel delivery.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

I was thinking lack of fuel, but wouldn't it fire on the starting fluid through the intake.