Need help - 2009 CLX - Stutters and misfires getting up to highway speed
Thread Starter
|
Junior Member
Joined: Jan 2025
Posts: 1
Need help - 2009 CLX - Stutters and misfires getting up to highway speed
Ok, my in-laws need help and so I'm turning to the internet! Sorry it's long winded, but there has been a few things attempted so best to put it all out there
Story goes my little old Mother in law, she bought this Lucerne new and has driven it for approx 350Kms or 225,000 miles, it's been a great car.
This summer, it started having issues starting occasionally and left her stranded once, my father in law an old farmer decided to replace the spark plugs. Napa gave him the wrong ones, (I told him they were wrong before installing, he believed Napa) the ones they gave him were for a 2008 Buick Lucerne with the 3.8L not the 2009 with the 3.9L. They replaced the plugs in the shop, and now the car won't start at all. Brother in law checked it over, no fuel pressure at the fuel rail so fuel pump isn't running. He said he googled it and read about the fuel pump and fuse panel issues, so he checked that first and the relay looked fine not burnt nothing obvious. So they bought a new aftermarket fuel pump from Napa... installed... car now starts and drives.
In-laws went for a trip to see a grandchild's graduation, during the trip the car stumbles and misfires a little throughout the trip, car quits after a few hundred miles and won't start. I drove a couple hours to help them and give them a ride, found the fuel pump relay burnt and the fuse panel slightly melted underneath. Grabbed another relay and swapped it out with the burnt one, car started and we made it to the grad. Next day there is an auto wrecker nearby, we go to see if they have any fuse panels... all of them have been stripped out of the cars! Huh... obviously a problem. Anyway I grab a handful of same relays and say hopefully it'll get the car home where we can check it out better. It did... now my father in law has a habit of whenever the car stops... he just swaps out the burnt up relay and the fuse panel keeps getting more melted. I said there is an issue obviously with the new fuel pump since it's burning relays... we didn't even put in the backseat for awhile to make sure nothing was being crushed or squished. Eventually by the 4th relay or so, it won't start at all fuse panel is melted all to crap around the relay. I happen to look at a local wrecker nearby my place, they have a recent 2009 Lucerne CXL... I go... it's identical... fuse panel looks like new... I grab it and grab the fuel pump from the car, was like $80 total and I believe the pump is OEM. I put the pump and fuse panel in, car runs again!
Car has been running since, fuse panel is not melted, relays not burning up... but thousands of miles later it still is misfiring when trying to get up to highway speed. Idling around the city, it's fine no issues...
So.. inlaws take the car to the GM dealership, first thing they say "You have the wrong sparkplugs", so they change them. Still misfires they say on Cylinder 3... they replace the ignition coils... say problem is solved no more misfires being recorded and give back the car... still misfires on the ride home. It's been back to the dealership now 4 or 5 times, they've done compression checks, they've hooked it up to the computer while on road test, driven it all over, they can't figure out why it's misfiring or what the problem is. Last time they put injector cleaner in the fuel and said good luck unless the check engine light comes on because without any codes they can't figure it out. They said if we want to dig deeper into it they want to start ripping apart the motor to see if there is an issue. I'm not sure if the misfire is still only on cylinder 3 or not, there is no codes and the GM tech notes didn't mention it the last couple times it's been in.
SO brings me here. I'm fairly mechanically inclined, rebuilt/replaced dozens of motors and transmissions over the years, farm on the side... I'm not sure where to even begin with this car. Inlaws don't want to sink much into it being it's 16 years old and quite alot of KMs... so if we can't figure it out on our own it's likely going to an auction sale with issues and we will get peanuts for it.
My gut feeling is for starters new spark plug wires... I didn't see wires on any of the invoices (I see coils and plugs...) but I'm not holding much faith that's the issue... could the fuel pump be the issue? For sure it could still be, it's a used pump... but I'd almost need some indication while driving to monitor the pressures so not easily figured out I'm thinking. I've read online it maybe a throttle position sensor... maybe? I could see it causing an issue if it's somehow while getting close to highway speeds getting wrong readings? Problem is in my brain shouldn't the dealership have seen that on their computer while driving the vehicle????
Anyway, long winded I apologize. If anyone has suggestions or seen issues like that and have a fix I'd appreciate it. Hoping to keep this car if possible, cause it is nice
Story goes my little old Mother in law, she bought this Lucerne new and has driven it for approx 350Kms or 225,000 miles, it's been a great car.
This summer, it started having issues starting occasionally and left her stranded once, my father in law an old farmer decided to replace the spark plugs. Napa gave him the wrong ones, (I told him they were wrong before installing, he believed Napa) the ones they gave him were for a 2008 Buick Lucerne with the 3.8L not the 2009 with the 3.9L. They replaced the plugs in the shop, and now the car won't start at all. Brother in law checked it over, no fuel pressure at the fuel rail so fuel pump isn't running. He said he googled it and read about the fuel pump and fuse panel issues, so he checked that first and the relay looked fine not burnt nothing obvious. So they bought a new aftermarket fuel pump from Napa... installed... car now starts and drives.
In-laws went for a trip to see a grandchild's graduation, during the trip the car stumbles and misfires a little throughout the trip, car quits after a few hundred miles and won't start. I drove a couple hours to help them and give them a ride, found the fuel pump relay burnt and the fuse panel slightly melted underneath. Grabbed another relay and swapped it out with the burnt one, car started and we made it to the grad. Next day there is an auto wrecker nearby, we go to see if they have any fuse panels... all of them have been stripped out of the cars! Huh... obviously a problem. Anyway I grab a handful of same relays and say hopefully it'll get the car home where we can check it out better. It did... now my father in law has a habit of whenever the car stops... he just swaps out the burnt up relay and the fuse panel keeps getting more melted. I said there is an issue obviously with the new fuel pump since it's burning relays... we didn't even put in the backseat for awhile to make sure nothing was being crushed or squished. Eventually by the 4th relay or so, it won't start at all fuse panel is melted all to crap around the relay. I happen to look at a local wrecker nearby my place, they have a recent 2009 Lucerne CXL... I go... it's identical... fuse panel looks like new... I grab it and grab the fuel pump from the car, was like $80 total and I believe the pump is OEM. I put the pump and fuse panel in, car runs again!
Car has been running since, fuse panel is not melted, relays not burning up... but thousands of miles later it still is misfiring when trying to get up to highway speed. Idling around the city, it's fine no issues...
So.. inlaws take the car to the GM dealership, first thing they say "You have the wrong sparkplugs", so they change them. Still misfires they say on Cylinder 3... they replace the ignition coils... say problem is solved no more misfires being recorded and give back the car... still misfires on the ride home. It's been back to the dealership now 4 or 5 times, they've done compression checks, they've hooked it up to the computer while on road test, driven it all over, they can't figure out why it's misfiring or what the problem is. Last time they put injector cleaner in the fuel and said good luck unless the check engine light comes on because without any codes they can't figure it out. They said if we want to dig deeper into it they want to start ripping apart the motor to see if there is an issue. I'm not sure if the misfire is still only on cylinder 3 or not, there is no codes and the GM tech notes didn't mention it the last couple times it's been in.
SO brings me here. I'm fairly mechanically inclined, rebuilt/replaced dozens of motors and transmissions over the years, farm on the side... I'm not sure where to even begin with this car. Inlaws don't want to sink much into it being it's 16 years old and quite alot of KMs... so if we can't figure it out on our own it's likely going to an auction sale with issues and we will get peanuts for it.
My gut feeling is for starters new spark plug wires... I didn't see wires on any of the invoices (I see coils and plugs...) but I'm not holding much faith that's the issue... could the fuel pump be the issue? For sure it could still be, it's a used pump... but I'd almost need some indication while driving to monitor the pressures so not easily figured out I'm thinking. I've read online it maybe a throttle position sensor... maybe? I could see it causing an issue if it's somehow while getting close to highway speeds getting wrong readings? Problem is in my brain shouldn't the dealership have seen that on their computer while driving the vehicle????
Anyway, long winded I apologize. If anyone has suggestions or seen issues like that and have a fix I'd appreciate it. Hoping to keep this car if possible, cause it is nice
Thread
Thread Starter
Forum
Replies
Last Post
mcafc98
Roadmaster
5
Feb 17, 2019 12:00 PM
