I have a 1990 firebird with the 3.1l and I have been realized that when I start it to warm up, it sucks more gas then it does when I am driving it and I want to know why it does that. My other question is, one day. I was on my way back and I was at a stop sign and their was a car coming, so I put my foot to the floor to and it just died on me, it started right up and drove ever since that.


Asked by Feb 10, 2014 at 01:00 PM about the 1990 Pontiac Firebird Base

Question type: Maintenance & Repair

Sucking gas and sometimes it won't start and die on me when I put my foot to the floor

6 Answers

Norm Davis

Your car isn't using more gas idling than driving, but keep in mind that you are getting zero MPG when it's warming up, so your mileage really suffers if you do this. Bogging - losing power or stalling under hard pedal - can be fuel or electric issue, but is most often dirty or failing fuel injectors. Try a couple of injector cleaning treatments and see if you notice any improvement. If it's still bogging and stalling, it will probably throw a code for you. Post it here and we'll go to the next steps.


Alright, I will get back with you on that.


It could be for sure. I've been digging deep lately with '88 to '95 GM OBD1 EFI systems since turbos are all the rage these days. Your car is the 3.1 MPFI and is a Speed Density system, I'll give you a brief low down. When you first start the car the exhaust and O2 sensors are cold and cannot read the exhaust and are not used, this is called open loop. The car starts and runs on the factory programmed fueling tables, mainly based on your MAP (Manifold Absolute Pressure, engine load) reading. The tables use inputs from the sensors to select the pulse width of your fuel spray cycle. Once the ECT (Engine coolant temperature) sees a certain engine temp the vehicle enters closed loop. The o2 reading is used to scale a multiplier in the calculation for your instantanous fuel. This mutiplier is what brings your air fuel ratio to the target setpoint. So long story short if you have sensor errors or any engine modes that would effect the stock airflow at all it will effect your idling a/f ratio until the closed loop can correct it. If you are interested it what if layed down I recommend getting a ALDL cable so you can read the live values in your car. That way you know what it's doing. $80.00 software is free from TP. P.S. That was very general, it's alot more complicated but I'm slowly getting there.


As for the bogging I'd hit were Norm was going. Ohm the injectors, clean them if there good. Check the fuel pressure and maybe change the filter.


Alright and the only I change and the guy I got the car change was he put ford spark pugs in and I change the air filter in it... Could one of those cause it to do that? And it only happen once on,


Well spark plugs have different heats. Cross reference what you have with the ones that are in it. Might have to go to a parts store and look at there book. If it's close make sure there gapped right, clean and test good to go. You can check the air filter. You claim your buring more fuel at idle so running rich if you follow my logic above your air flow could be restricted. The cables nice because you can see what state the o2 is in before closed loop and monitor IAC or EGR. I just got mine and I won't even look at a problem know without it.

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