New Member From Iowa


New Member
Hey Everyone,

I'm a newly registered member from Des Moines, IA. I picked up a 1987 Buick Grand National with 86000 miles about a year ago. This car had been sitting for around 15 years. It had been involved in a wreck 2 owners ago. I purchased the car from a close family friend who has been a part of the Buick community for a pretty extensive amount of time. He has attended the buick nationals in Kentucky numerous years along with my dad. He planned on restoring this car but ended up picking a 40000 mile one up and decided to part ways with this one.

When I got the car it needed some engine parts put back together and the new body panels needed to be aligned. I've been slowly chipping away at it for the last year. I'm up against a mechanical issue right now I cant seem to get figured out. It's currently back firing through the intake under any throttle. Any help would be greatly appreciated.

Current mods:
2.5" Downpipe
Flow Master Exhaust
60lb Injectors
Turbo Tweak Chip
Adjustable Fuel pressure reg
Racetronics 255 fuel pump
Ported throttle body
Ported dog house
Power plate
Upgraded 02 sensor
GN1 Radiator
LS1 Maf
Maf Translator
New plugs/wires
New Coil pack
New Ignition Module
Scan Master

My Grand National

I also own a 1982 Mercury Capri. I've 2jz swapped it backed by a built th400 and a precision pt8685. We do quite abit of no prep racing around the midwest. The car has been 5.65 @ 123mph on the stock botton end.


1986 Buick GX1

GX1 #001 [The One and Only]
Welcome from North Central IA. Great rides. I love those Capris (I mean, like, there ok dude).

Back when Capris were cool cars, not short pants for girls.


Well-Known Member
Welcome! - Cool Cars!

You have to respect 2JZs - love the transplant!
Im pretty sure there's a decent population of Iowa Buick owners...

Does Austin, Keith and JD [TurboFarm West] still live there? If so do you know them?



New Member
Thanks everyone!

I know of Keith but never met him before. I haven't heard of the other two. I know a few other turbo buick guys but nobody well enough that I feel good asking for help.

It does have fresh gas that's almost exactly when it happened. I had considered maybe the gas was bad but I fill all my vehicles up there including the capri.

I did some pretty extensive searching last night. I'm going to try testing the cam sensor by unplugging it while the cars running. Also going to check the main power lead to the battery and make sure it hasn't melted to the exhaust manifold. Other things I had considered was the crank sensor and tps. I recall the tps reading correctly with the car off. I was going to check it while running.


Well-Known Member
Also make sure the MAF settings are correct - if so, see if you can borrow a KNOWN good MAF to switch out and see if that helps.

Post the reading from your Scanmaster at idle and while part throttle [if you can].... maybe something will stand out.


New Member
Tps is .42 and I did check the maf settings in the translator and this maf came off a friend's running car when he went speed density.

I'm beginning to think maybe the used fuel pump I put in is having a problem.


Active Member
Welcome aboard! There are quite a few Buick guys around that area. I’m over by Cedar Rapids myself.
Definitely check cam sensor. If it’s 180 off it could cause those troubles though I’ve heard of some cars driving around 180 off for years.
Sounds simple too but check spark plug wires and make sure they’re going to the right holes.
You mentioned in the first post about having an upgraded O2 sensor. What do you have? There are some that are known to cause troubles.
Thank you! I'll check the cam sensor. Is there tutorial somewhere on how to check it? I've checked the wires but I can check them again and make sure.

This is the O2 sensor kit I have it doesn't have a name on it.



Well-Known Member
As mentioned previously thats a Caspers Electronics heated O2 kit. Your numbers look good but i believe you are still in Open loop and the car isn't warmed up and not running off the O2 yet.... how does it run when the car goes into closed loop and when does the actual backfiring happen?

I'm also curious to see how the O2 numbers fluctuate at closed loop.

Thanks guys I really appreciate the help! Ill check the cam sensor tonight and let the car warm up and get some more video.

Is the Casper's o2 kit a decent unit? Looks like it's made well.

1986 Buick GX1

GX1 #001 [The One and Only]
The heated O2 sensors are more tolerant to leaded race fuels sold in the past. That's why I had one. With E85 I didn't think it was necessary so I removed it. Mine was not a nice plug and play unit like yours though, and I wanted to clean up some wiring anyway.

There may be other benefits as well.