rsilver

I still need to work on a new chip for my swap, but does anyone know what would cause
popping (almost like a backfire but not as loud) coming from my muffler when I decelerate or shift gears? It pulls very strong but when you let off it pops. Any thoughts are appreciated..........bob

------------------
91 camaro RS convert,GM crate 350 with LT1 cam,edelbrock 6085 heads,9.5:1 comp, edelbrock TBI intake, 65# injectors, GM cop chip,dual fan conversion,
ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back,Flowmaster,
T-5, centerforce 2 clutch, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets, edelbrock STB

BadBowTie

it could be that your timing is advanced just a bit to much.

Mark305TBI

Could be oxygen getting into the exhaust. A bad header gasket, exhaust leak, ect.

-Mark W.
'88 SC Camaro /w 305 TBI

JPrevost

You obviously have unburnt fuel so you're either a) Running rich, or b) Cylinder missing. I'm going to go with a) since you said it pulls strong. Do you have the AIR system still hooked up? What about the CAT? What ecm are you running with (stock 8746 or 7747)? Either way, if the car isn't running rich then you'll want to edit the deceleration table. It sences the TPS position over time and if you let up real quick it'll look at the MAP pressure etc. and cut off the fuel and ignore the engine rpm. Check your spark plugs, I'll bet they show you're running rich all the time.

------------------
, Jon (350 TBI!)
91 Red My website

rsilver

JP, the air system is hooked up, I am running
a cat and the ecm is the 8746. The plugs look all right to me, maybe a little rich, but not a ton.Your comments on the deceleration table is very helpful.The cop chip is for an automatic and I have a t-5 so there is probably a difference on deceleration. I am going to try my 305
thermomaster chip and see what it does to the problem.
I think I also have an exhaust leak.I just noticed it tonight, very slight either by the header or header pipe. Still not sure.
Anyway, thank you all for your help.I got 1100 miles on it and so far so good.......bob

snflupigus

rich with exhaust leak is usually the prob when it comes to that. my 69 does it horribly. cuz its carb, and the exhaust is rusted to hell and gone.

JPrevost

No prob, just get all the things you know that is wrong fixed. Then move onto the more complicated stuff like eprom tables etc. It's usually the simpliest things that make the car run the worst.

------------------
, Jon (350 TBI!)
91 Red My website