I hope some of you guys who are experienced with TBI can help me out cause I'm at a complete lose here. My truck which is a 305 TBI as rough idle (shacks the truck at idle, smooths out crushing). The computer did show codes for map sensor and coolant sensor. So i have replaced map sensor, coolant sensor, rotor and cap, spark/wires trying to fix this problem. I do not have a RPM gauge so cant say how high its idling, but it changes. I also have not check the fuel pressure since i have to put an adapter on and buy a gauge to do it..

It is sucking fuel down, way more then it ever as. So today i was just looking at the engine and thought what would happen if i unplug an injector(as 2, but u guys know that I'm sure). Well i did and the truck smoothed out and idled and stopped all the shacking, surging etc etc. So my question is what do you guys think my problem is. I have already spent tons of money listening to part guys who seem to know nothing, and garages. Any help would be great.

P.S: I have check all vac lines and have not found any leaks, i have not check the gasket under the TBI yet.

Thanks

 

So its too much fuel? You try opening the regulator to see if theres anything wrong there?

 

Yes it will suck half a tank of fuel down in under in under 20-25 miles. At watching the injectors you can see it just spraying tons of fuel into this thing. I have not pulled it apart to look at the regulator, but its pretty cheap to replace that. I just already spent over $200 in sensors etc, so hate to just keep buying new stuff without knowing if its really the problem.

However if u want me to pop it open and look at the regulator i can, any idea what you want me to look for( pretty sure just to see if its leaking).


Thanks

 

If the FPR is leaking you will see fuel pour out and down the TBI bores.

Pull some spark plugs out and look at them. If the fuel is going through the engine they will be completely carbon-ed up.

The next step would be to get a scan tool on it and look at what the sensor readings are.

As for the coolant sensor (CTS), I would also replace the pigtail for it. They tend to corrode over time. Which tells the ECM that the engine is colder then it really is, and dump fuel into it.

RBob.

 

Yes they have light carbon on them (all of them have the same amount). The injectors are shooting out the fuel pretty uniform(but tons of it)so don't think they are the problem, also i have not checked the regulator yet.

 

regulator don't seem to be leaking, but guess I'll replace it. More then then likely with an inline one since i cant seem to locate the problem.

Thanks