82z28macdady

iTrader: (5)

long story short, i had a 98 ls1/4L60e in my 87 Firebird until i spun a bearing in December and bought a 5.3 to replace it.

I was hoping that when i went to fire it over, my ls1 computer (which had a little tuning done to it) would be able to compensate enough to run. I didnt think it was going to run well, but i just wanted it to move. Right now It backfires at idle and sounds like its missing and has a healthy amount of black smoke exiting the tailpipes.

some things about the setup
99+ fbody computer and harness. uses all the sensors off the ls1 block.
LM7 with an ls6 cam, ls6 intake, 853 heads, long tubes, and uses the stock 98 injectors.

whats the easiest/cheapest decision from here?

Doc

iTrader: (9)

What did you do with the three interconnects behind the passenger side kick panel? The 98 Fbody has three, 99+up have two.

We could get you on the right path with a mail order for $125 shipped inside of Florida.

Doc

82z28macdady

iTrader: (5)

my brain is fried after all the crap I've done today on trying to figure this out lol. Could try to explain what you mean by the 2 interconnects?

thanks for looking!

Jaysz28

iTrader: (19)

it'll run ok enough to check for leaks and what not

I did something similar with mine and the only real issue i had was horrible mileage until I got it dyno tuned.

I wouldn't daily drive it without a tune though.....

Glad to see you decided to keep the car. I was really wanting to buy it, but I have 4 cars now and don't need another.... lol

-jason

jimmyblue

iTrader: (11)

You're going to be pretty overfueled until you get the
injectors (28.8 '98 vs 26 '99) and displacement (5.3
vs 5.7) set. Not going to idle very well at double-fat.

Mike Norris

iTrader: (10)

I am guessing the 98 engine in the 87 ran well before hand. My question is did you swap all of the sensors off the old engine over to the new engine (MAP, IAT, MAF, Coolant Temp, Crank Sensor, Cam Sensor, etc.) ??

Somtimes when you mix and match sensors with the wrong computer things can go wacky. If you did swap everything over, it should run at least better then you describe. If it is backfiring and huffing out black smoke, I would check:

1) MAP sensor getting vacuum, this would show excessive load at idle.
2) Coolant temp sensor unplugged or broken. This would read -38* and make her run rich.

After that ther is what Jimmy mentioned also. If you can scan and see if there are any codes or at least see what the MAP and coolant temp it is reading and go from there.

Hope this helps.

Mike Norris

ddnspider

iTrader: (26)

The car was originally tuned with the 98 injectors so that is a moot point. However I did mention that it would be rich strictly for the cam/ci differences. If he doesnt order a scan gauge we can make another cable up so he can use my aeroforce scan gauge to monitor coolant/map.

82z28macdady

iTrader: (5)

i'm so dumb. seriously i dont even want to put this up on tech right now....

little wire pulling and brain scratching led to finding one of the coil harnesses is on backwards. that sure would cause a misfire if i ever heard one. I'll post when its running tomorrow

Mike Norris

iTrader: (10)

Don't feel bad, I have seen that before when switching the coils from the older valve covers to the 99 brackets. I think on two cars. They were quite a while ago and I feel bad I did not think of it before.

Hopefully all else will be good.

Mike Norris

82z28macdady

iTrader: (5)

started right up this time! shocked


i'm dumb, the end

Jaysz28

iTrader: (19)

glad you got it sorted out man!