Hallo I m the only nut driving a Firebird in Belguim with gas at 2dollars40 a liter but hey I still love the car. I have a problem my car drives great when its cold. rev around 550, 600. But when I drive it for a time on the highway or in the city all of a sudden it goes up and down from 400 to 1200rev and then it drops and the engine just dies, and with all the power out its becoming dangerous. I have changed the idle control, put new spark plugs, wires, rotor, air filter but nothing helps so can anybody helppppppppppppppp

 

Well for starters your tach must be off if its at 400-1200 rpms at highway cruising speeds, should be in the 2-3k range.
As for the issue at hand, possibly injectors or fuel pump, I would check the injectors first, could be the MAF or tps acting up as well possibly. Does it do it at other speeds, like does it seem more speed or time sensitive? ie. if you drive around for 10m it stalls, or it stalls when driving at 55 mph for a bit?

 

Merci for your interest, It drives perfect on highway at any speed, it only starts acting up when I go off highway and let go off the gas, it then goes up and down. When I give a little gas its good again for like 2,3 miles and starts up again. Two times I had my engine fall out and no power anything, so I put in neutral while driving and just turn the key and its ok again. If im standing before a red light and just gave a little gas before the rev stay perfect at about 600 to 700.

 

Is the stall immediate, or does it stutter? And that sounds like a fuel issue to me, you should check that the injectors are giving off the right resistance, and check the fuel pressure as well, maybe your FPR is bad. Doesn't sound like a sensor from what you describe though, my bet is on fuel, but maybe check that the EGR valve isn't getting stuck open or closed also. Btw, as I understand it, it starts back up right away with no drama?

 

are you saying it idles high after you first start it then after you drive for a minute it goes down?

if so thats normal!! all cars idle high when cold, after they get to the opperating temp they drop down.

 

Common issue with the 90-92 cars is a wiring issue in the ignition system. A couple people here have gotten their whole engine harness replaced due to this issue. Personally, I had been using a harness and ECM from a 90-92 car (from a 91) that ran just fine until it was allowed to get good and hot. Then, it would shudder, and shortly after that, it would die. How I know it was an issue with the harness was that, with my old harness installed (only need to change around about 4 wires), I could drive for 9 hours straight with no issues, on the same parts.

May want to go to a shop that knows something about computerized engine controls and have them do some tests on the ignition wiring.

 

Thanks Dav, I will go on saturday, hope it helps Merci