TBI problems - NJFBOA - Home of New Jersey's Camaros and Firebirds

Batman · 08-23-2005, 05:36 AM

Well my Formula has been down and out for about a month now, mostly due to lack of time to work on it. It has been backfiring through the intake manifold which I figured was the kiss of death. CHecked the timing chain and all the valvesprings, everything is fine, no binding in the valvetrain at all. Car idles fine but under load it breaks up. I am leaning toward fuel injectors now, going to rebuild the whole T/B and then pull the whole exhaust and look for obstructions. It feels kinda like a plugged Cat but the cat was gutted months ago and the car ran fine, maybe a piece was inthe intermediate pipe. Anyway any other ideas I could use a little help.

90FormulaWS6 · 08-23-2005, 07:44 AM

check ALL your vacuum lines especially the one that goes into the back of the TB

Fasterthanyou · 08-23-2005, 02:25 PM

Backfiring through the intake is almost always fuel starvation. Have you replaced the fuel filter? What about the fuel pump? Those are the 2 things that need to be replaced on old TBI vehicles.

Pampered-Z · 08-23-2005, 04:59 PM

How old is the gas? Â*Could it be bad or have water? We wasted weeks chasing a simular problem on a TPI Vette that sputtered and ran like crap. Â*we replaced all kinds of parts, injectors and FP regulator then went to change the FP. When we dropped the tank we found a few gallon of water in it! Â*

Maybe some type of timing issue? Â*If the T-chain is OK, could it be something within the distributor or wires?

Batman · 08-23-2005, 08:42 PM

Gas is new, filter is new, pump is an unknown. I am putting my ported TBI on now anyway so if it doesn't work and nothing else is found the pump is next.

Fasterthanyou · 08-23-2005, 11:47 PM

The pump is a wear item. When it wear's out you need to replace it just like anything else. The problem with OBDI is that it doesn't tell you the pump is the problem but it's pretty easy to self-diagnose. Just hook up a FPG and tape it to the window. When you snap open the throttle while driving down the road does the pressure drop as if the pump can't keep up? Almost every stock TBI fuel pump does this after 100k miles, they're that pathetic. Replace with walbro 190 for 350hp and no more than 150hp of nitrous or just go straight for the 255 if you're not sure if you'll be staying with TBI.