My '82 Trans Am which has a rebuilt 305 with only 800 miles on it is giving me a check engine light when I drive on the highway. It happens when I drive 55 or more mph for a minute or more (which is 2200 rpms or greater). I have not been able to find anything wrong with my car, the temperature is fine and the engine runs great. The only thing I notice is that the Oil Pressure gauge always shows 60 or more when the check engine light comes on. However I figure for a rebuilt motor going 2,200 rpms or more that this would be normal. Does anyone have any ideas of what the problem may be. Thanks in advance for any help you can provide.

 

Pull the codes.

It's probably an O2 fault, either showing rich or lean. The mixture may in fact not be rich or lean, but the sensor might be bad.

Codes 44 & 45 are the ones for those errors IIRC.

 

i get that same thing eveyonce in a while... mine is the 02 not getting enough crosscounts and throwing a temp code... can't pull it w/ the paper clip trick... but w/ the scantool if i watch it when it happens i can see that its the O2

 

mine did the same but i dount we have the same issue...

i would assume you have and efi system... the engine might lean too much when it goes into highway-mode.. i don't remember how much it would lean out (a/f 14.7:1 to 12.?:1 i think) but it does to save fuel.. i would say you have a bad o2 sensor since i undertand that the car work w/o error codes in the city??? but more to do with ignition and the leaning out... the o2 sensor would not throw a code when the engine is leaning out if its bad.. i think my o2 sensor is bad some how and giving a constant reading even thow the mixture is of... just my $0.02

correct me if i'm wrong..

 

Thanks guys for the info. Next time I drive it I will find out what code it is registering and I will check out the Oxygen Sensor the wire that connects to it.

 

why is it turning that many rpms, is overdrive working? once i get to 55 and OD kicks in it runs like 1700rpm.

 

Tekviper,
My '82 Trans Am has a T200C (3-speed automatic) transmission, so I have no overdrive gear. The '83 Trans Am was the first Trans Am that came with a 4-speed automatic transmission (700R4).

 

Mine did that. For me the vacuum line for the EGR fell of the TB.