SBC TBI issues

[CRZA1]

Well I bought an Ebay cruiser a while back and am now finding time to play with it. Its an 83 with a 2.5 OME spring under, with a 305 SBC and NV4500. Well the guy I got it from said it had vapor lock issues at ambient temps above 70. Occasionally had problems but it was witer and it drove home from denver no problem. Now its summer.

1. I checked the pump and it was a carter rotary vane type for a carbed motor, so I replaced it with a proper EFI pump. High flow and high enough pressure.

That fixed the drippy injectors, and I now am getting a good spray pattern from the injectors.

Now the problem. The guy or who ever installed the motor had the thing tuned super rich to run the thing with the crummy pump. Now I get a dark smoke from the tail that smells like gas, and it doesnt hold load above 2000 rpm.

Is there a quick and dirty way to tune it correctly?

Any help would really be appreciated, I want to drive my cruiser!

Thanks, Chris

 

[LCOwner]

Is the throttle position sensor adjustable? You might be able to back that off. What kind of shape is the O2 sensor and is it close enough to the engine to keep it hot? If it's too far away you might need a heated unit.

 

[CRZA1]

Where might the TPS be, and how would it be adjusted? I can find it on a multiport system, but dont see anything similar on the tbi unit.
The O2 sensor is mounted just after the exhaust manifold on the passanger side. Looks to be close enough.

Thanks. Chris

 

[CRZA1]

So I fiddled around a bit and removed the (or what I believe to be the) throttle position sensor plug and the thing started running better. I narrowed it down to the TPS or the IAC. It was a square plug on the passanger side of the throttle body. Still getting a bit of black smoke. Also the engine check light came on.

So now where to go from here? Is there a better source of info on trouble shooting this setup, or on tuning it?

Again any help would be much appreciated.
Thanks. Chris

 

[rockyklg]

i think you need to set the tps to +.05v at idle. its straight forward enough. check codes for the check engine light. probably a rich or lean code. replace the o2 sensor for good measure and make sure your pump is capable of at least 15 psi. iac and coolant temp sensor prob not a bad idea either. the sensor are all cheap so it cant hurt to replace them. oh and replace the fuel filter. hi pressure fuel filter(just in case they used a clear plastic jobby)

 

[LCOwner]

It really sounds like one of the sensors is telling the the computer it needs more fuel. rockyklg is right, replacing the sensors id cheap.

 

[OlympiaFJ60]

So I fiddled around a bit and removed the (or what I believe to be the) throttle position sensor plug and the thing started running better. I narrowed it down to the TPS or the IAC. It was a square plug on the passanger side of the throttle body. Still getting a bit of black smoke. Also the engine check light came on.

Square plug is the IAC, the TPS should be a round 3 wire or flat 3 wire. Same area as the IAC though.

If the vehicle was tuned with the low fuel preasure it will be over fueling at the higher psi. It can correct it over time to a point. Check with a local performance shop or try one of the online guys like JET or Howell. Tell them what you have and the can make you a good chip for a few hundred dollars. Or you can go to the junk yard and get an ECM out of a similar vehicle and switch it or the EPROM.

One last thought, unplug the ECM to reset it, plug it back in and see how it does. Maybe it has just adapted to the low preasure.

HTH