: LD8 Engine issue (2005 Bonneville GXP)

02-20-08, 12:20 PM
I apologize if this is in the wrong place, but I'm in extreme need for a solution to the problem I'm having with my car. I have a 2005 Bonneville GXP with the 4.6L Northstar engine. The engine has 46,600 miles on it. I'm basically desperate to find a solution because I need this car to get to work in the morning. I've posted this in the Bonnevilleclub.com forum and the w-body.com forum, and have heard suggestions that it is a misfire and might be the spark plugs, spark plug wires, ICM, or coilpack, the latter of which will be a rather expensive repair if its not under warranty. I have worked on engines before so I know my way around a bit if I end up having to fix it myself.

Here's my story:

The other day I was making a left where two turn lanes make a left. I pull up fast and brake hard at the red light, and there's this Ram 3500 Cummins turbo diesel, so we take the turn and I gun it to pass him so I can get into my turn lane to go home, reaching 6500 rpm in the process in first gear.

Then I come to a stop at the next red light, and the engine is fine, till I feel a bump. So I'm like wtf? Does someone have an insane set of subs in their trunk next to me? Till I realize I'm not hearing any bass and that is coming from my engine. Then I feel another bump, and another (gradually increasing the frequency of the bumps), till my engine constantly idles really rough, to where you can feel it shaking the car. Acceleration at low RPMs is very rough as well, with some apparent hesitation, and my whole drive home on the highway I was getting no better than 19mpg at 65 mph. I also had a noticeable decrease in power from before, and the service engine soon light was blinking.

Oil level is fine. Everything seemed fine, it just didn't *feel* right. I took it into the dealer that I bought it (a Nissan dealer), because I had bought a 4 year/48,000 mile powertrain warranty with a $50 deductible. Unfortunately, my warranty wasn't processed yet so I couldn't use it to get my car fixed. It will probably be another week or two till I can take it in.

So I'm sitting here wondering what in the world could the problem be. My Regal GS with the L27 engine has 172,800 miles on it and I've been riding on wide open throttle for 100,000+ miles and never had so much as an oil leak.

Anyone here have any ideas what could be wrong? If I can fix it myself for $50 or less, I'll just do that instead of taking it to the dealer and arranging for someone to pick me up. I can rent a code scan tool to see what code my car is throwing out for the problem if that would help anything.

If not, I have to wait for my warranty to kick in so I can take it in and hope that this problem is covered under my powertrain warranty.

02-20-08, 12:53 PM
pull codes? (im gonna bet that your car doesnt have on board diagnostics like ours so take it to advance auto parts and ask for their code reader)

without anything id say this is a job for AJ

02-21-08, 12:16 PM
IF the check engine light was blinking--the code will reveal the issue. You can get it checked free at AutoZone too.

02-21-08, 06:58 PM
A blinking/flashing MIL lamp is not good, it indicates a severe misfire that could damage the catalytic converter. Bad spark plug, coil or injector. Like Jason said pull codes and stop driving it or your cat will be toast.