Hi, I just purchased a 1991 Firebird with a 3.1 v6 and an automatic that was none running when I bought it. I was hoping to get lucky and maybe find just an alarm problem but instead I just inherated someone elses gremlins . Ok here it goes, The car will crank and even start but only for a split second and then it dies again and sometimes even coughs out of the throttle body like its lean. The Fuel pump was replaced earlier this year after the car had been sitting for a few years and it ran fine for about 50 miles then the car just quite and the guy got fed up and sold it to me. I've tried everything first we changed the ingnitionj module then the computer I even tried changing the map sensor and the fuel pump relay. The pump turns on and if you start the car on spray it will run for hours. I checked fuel pressure and got 41 pounds while running but with a leaky gauge so probably a little more. So far all I have is a pretty blue firebird with lots of new parts that I still cant drive SOMEONE PLEASE HELP oh yeah one more thing I unplugged one injector to see if I could get a pulse and all I got was a steady light with no pulse.

Anybody Please

 

hey, when u said cough out of the manifold did u mean sort of like a backfire? like their was smoke or even a flame coming out of the manifold? if this is the case, then it is timing related, the timing is off. im a little new to all this but im trying to be as helpful as i can! goodluck!

 

Im pretty sure its not timing. It doesnt cough like a backfire Theres no flame and also if you spray fuel in the plenum it runs just fine. Im pretty sure it's not triggering the injectors can anybody tell me what actually triggers the injectors on a 91 3.1? What physically tells the injectors to fire?

 

Before we get too far into this, let's make sure a couple basics are okay first. Check all the electrical connections for the distributor, coil, alternator and fuel injectors to make sure they're not loose or faulty. Then make sure the intake, fuel injection bolts are at their proper torque. Quick questions.
1. Do you know who put the fuel pump in?
2. Did you say the car will start and run on starting fluid?

To answer your question. The E.C.M. controls the fuel injectors. The way the E.C.M. determines how long the injectors are to be opened is by the information it receives from the Engine Coolant Temperature, Exhaust Oxygen Content, Throttle Position, Intake air mass, engine R.P.M., Vehicle speed and accesory load. The most likely candidates for bad sensors that could cause this problem are the Coolant Temperature, O2 and Throttle Position sensors. Which is what you should check after doing the preliminary checks I described earlier.

 

Yeah...check all the stuff iroczracer07 recommends. If they all check out, then it may be injectors. Bad injectors can kill the INJ drivers in the ECM and a new ECM may have only run for a short time (50 miles, for instance) before frying. To check, disconnect the connectors from the injectors and check the resistance across the injector terminals. I forget the number, but IIRC, 12-16 Ohm is good. Too high/too low and they're bad.

 

Thanks for all the information! I got my hands on a noid light last night, and i checked the passenger side injector. (only one you can get to without removing the plenum) when you start the car by spraying gas in the front of the plenum the light comes on when the motor first fires, and then slowly fades after a second or two. would that indicate that the computer is bad or sensor is bad?

 

Ok I replaced the Temp sensor and the Tps and it still wont run. Is there anyway I can test the other sensors to see if they are bad before I buy them? This is getting very expensive. I think the only sensor I haven't replaced so far is the o2 sensor but I really dont see it causing the car not to start but I could be wrong. The car still wont trigger the injectors they pulse once like maybe cold start or something and then the noid light just fades away to almost nothing its still on but just barely.
If I dont figure this out there may be a pretty blue v6 firebird for sale soon

 

Any of the sensors would have thrown a trouble code. Quick assessment for the O2 sensor is, does the car seem to be lacking fuel or smell of fuel when you're driving? If the answer is no, then your O2 is probably okay. As for replacing those sensors, did you test them first? The key here is to test things out before you go replacing them. I'm not trying to be a jerk, I'm just trying to save you some money. In all honesty, I think that you either have bad injectors or something didn't go right when that fuel pump was installed. I'm leaning towards the fuel pump. In order to be sure though, we have to check everything out first. Do yourself a favor and don't replace parts at random. Excercising some patience in diagnosing your true problem will not only help you identify the gremlin, but it'll save you some money too. Do you know if the guy who sold you the car is the one who put the fuel pump on?