Adam_87

I have an 87 305 TPI. The original owner said he had ported the heads and intake manifold and well as put in a mild cam. What the engine is doing is not idling properly or accelerating well. With no load it will accelerate just fine. With load it will move with my foot barely on the pedal but once i put my foot down just a little bit more it will spit, sputter, jerk and backfire. At WOT it will continue to spit and jerk and backfire until it catches up to higher RPM and accelerate fine, but still lacks power. The fuel pressure is at 27 while running and 35 with the vacuum line disconnected. I know it's supposed to be at 40 something but where I'm confused at is all 8 spark plugs are carbon fouled and reek of fuel. The tail pipe burns your eyes. Since I've owned it I have had a T56 transmission with a heavy duty clutch put in. I've replaced the fuel pump, filter, plugs, plug wires, distributor cap and rotor as well as ignition module, FPR and injectors. Vacuum is at about 13. The needle moves just a little but really not much. Not finding any leaks. The timing was at 0 but I put it at 8 following the procedure in the chiltins and by looking on here. Since re timing it runs a tid bit better and smells a little better but it's just not up to par. Also I hear this ticking sound coming from the back passenger side of the engine. Sounds like an electrical spark jumping to found but I can't see or feel anything. Any input is very much appreciated. Thank you all.

Barlow8869

iTrader: (1)

if it was ported, and cammed, it also needs tuned ... to check for spark, take it to a pitch black spot, and start it up get under the hood and look

Adam_87

How else does it need to be tuned other than what I've already tuned?

Barlow8869

iTrader: (1)

the computer needs to be re-tuned, the extra air and fuel that is getting in from cam and porting needs to be tuned into the computer, or it will never be right

Adam_87

So I need to take it to a performance shop. I was thinking about having the computer flashed or replaced. I'm not sure about what kind of cam has been put in, all I know is its a mild cam. Again thank you for your input.

Barlow8869

iTrader: (1)

if i were you, i would talk to Tuned Performance (on here) before i did anything

Adam_87

Okay. I sent them a message. Thank you very much.

armos

Fuel pressure is way too low. This is at least a major part of why it's misfiring. The ECM can't properly meter the fuel delivery at the injectors when the pressure is so far out of spec. Poor combustion leads to unburned fuel, which is why you smell it at the exhaust.
If it's really just a mild cam and some porting, that shouldn't be causing it to run this badly. ECM tuning would still be preferred but I don't think it's your primary problem.

Adam_87

Any recommendations for a fuel pump that will provide that pressure and will last a while? I have an AC Delco pump in now. It whines pretty loudly but is only a few months old and I don't drive much at the moment. I'm not noticing any restrictions in the line and the fuel filter is new.

Adam_87

I have decided to get an aeromotive GM 340 LPH fuel pump. Anyone have experience with this type of pump?

Chad85T/A

iTrader: (1)

The pump doesn't dictate the pressure. All the pump does is supply the amount of fuel to the rail. The fuel pressure regulator is what dictates the pressure. If the pump isn't very old that's probably not the problem.

Adam_87

I have a brand new regulator in it as well. I have an adjustable FPR and have found a longer screw VS the standard one that comes with it to adjust the pressure. I have that screw down all the way so it's just touching the base of the spring. So it should be causing maximum pressure at that point. Though I'm still getting the same 25-30 psi all the time. I think the pump just isn't putting out what it's supposed to.

Chad85T/A

iTrader: (1)

Now your giving more useful info. What kind of shape are the injectors in. If they are leaking it'll be really rich and not build any fuel pressure either.

Adam_87

Injecors are brand new 19lb bought from southbay. I've primed the system several times consecutively and the pressure remains and 30 engine off and 25 at idle.

Chad85T/A

iTrader: (1)

Another pump may be in order to just rule it out. I don't have any experience with that aero motive pump, but a 340 should be more than enough and then some. I have a walbro 255 and its great.

Adam_87

I've been thinking though. I'm really not sure about this. With the cam in it, I'm only getting about 13 HG for vacuum. Not finding any leaks. Needle isn't quite steady but pretty much there. With the added fuel pressure is that vacuum enough to pull the FPR spring up enough to allow excess fuel pressure to return to the tank? Will the added fuel pressure help lift the spring for fuel return so the cylinders don't get to much fuel?

Chad85T/A

iTrader: (1)

Idk for sure, and I dnt know what cam it has, but I do know there are people running bigger cams than you have and they're not having problems with that.

Adam_87

Okay. Well the pump arrives tomorrow. After installation I'll see where I'm at. Thank you very much for your input and advice!!

Chad85T/A

iTrader: (1)

Well I don't think I helped you much. Maybe somebody will read this and see what all you've replaced and have better input.

BOSTONCAMARO

dist.in right? correct number one being used as number one? im betting timing