View Full Version : Chevy Throttle Bodies Question Anyone??

01-28-2008, 11:05 AM
Throttle bodies are my weak point in the automotive world. Don't know much about them, so here's my question. Can the injectors wear out to a point of increasing the volume of fuel being used? My 93 Chevy truck, with a 350 in it is using more fuel than normal. It has new plugs, new ignition wires, distributor cap and rotor along with a new oxygen sensor. All top brand stuff. The exhaust pipes are black instead of dark brown as before. I'm wondering if the throttle body is the culprit. Any views on this situation? All possibilities are welcome. PJ

01-28-2008, 12:04 PM
your T.B.I. 350 chev has several sensors along with the Oxy Sensor there is a M.A.P. sensor {A manifold absolute pressure sensor} and a T.P. sensor {Throttle position sensor} Along with the Oxy sensor these other sensors tell the injectors Via the E.C.M. how much fuel to is needed. All of these sensors along with the E.G.R. system have to be working properly in order for the E.C.M. {Electronic Control Moduel} I.E. "Computer" to tell the Injectors to deliver the right amount of fuel. There are just simply too many variables to diagnose which sensor or injector/s are bad without scanning for codes.
Some places such as Autozone will scan your E.C.M. for you for free or a small nominal fee. The scanned code will tell you which part or parts are faulty. It is a Possibility that it could even be the E.C.M. itself.
My experiance is that you can chase these parts forever and still not come to a solution without the scann.
I hope this helps.

01-28-2008, 12:08 PM
Yes it is possible for the injectors to wear, but that is kind of hypothetical. Take the truck to someone who can do a diagnosis by data stream. This means they inspect all sensors as they work to tell if any are out of range.
Another possibilty is the fuel pressure regulator. If the regulator is defective then pressure is higher pushing more fuel through.
Check all the vacuum lines as a false air leak will also result in higher fuel consumption.
This is just a few quick ideas, hope it helps. Others may have more suggestions or more specific remedies.
Dave /bcforum/images/%%GRAEMLIN_URL%%/driving.gif

01-28-2008, 01:37 PM
Dunno what Chevy uses for their TBI injector but I've seen the Chrysler ones develop a leak. Fuel dripping from it down the throat as long as there was pressure.

01-28-2008, 03:28 PM
A guy at the local NAPA store just told me it is possible that a diaphragm in the unit might be leaking. That problem could be solved for about 30 bucks. But, I'm going to take the suggestions about having the system scanned first to make sure the sensors are ok. Thanks to all and will let you know what the scans turn up.

Doc, looking down the throat of the unit, it looks wet around the, I guess, pressure regulator? The edge of the diaphragm is slightly wet with fuel. Might be the culprit, but I'll have it scanned first. Boy, I wish this thing had a carb on it. Those I can fix.

01-29-2008, 04:48 AM
Update; I went to get a scan done on the truck and was told that the engine check light has to be on otherwise the scanner won't receive the code. It wasn't! But in the interim, I was told by two mechanics that the throttle body pressure regulator was leaking.
The culprit seems to be the pressure regulator diaphragm. It is weeping gas at a small but steady rate down into the intake manifold. Easy fix. Hope that's all that's wrong with it.

Oh yeah, to have it scanned without the engine check light on, It has to be hooked up to a regular diagnostic machine, such as one like a dealer has. Will have that done anyway. Thanks for everyone's input. PJ