Grand AM '92 gas milleage

Hi
I have recently purchased a '92 Grand AM V6 3.3l with 190 000km (120 000miles) and my gas milleage is realy poor. im doing 20liter / 100km (11.7 mpg). There is another thing, when the engine is between cold and hot(normal temp), the rpm always goes between 500 and 1000, like if i was pushing a few the acceleretor every second.

anyone got an idea of what's going wrong?
thanx

Original plug wires ?

If they have the cylinder numbers writen on them then chances are they have never been changed.

Original plug wires ?

If they have the cylinder numbers writen on them then chances are they have never been changed.

plug wire?
do you mean the spark plug wire ?

Yes, the spark plug wire's.

Yes, the spark plug wire's.

i dont think
because i remember when the car has been inspected (before i bought it). when the guy was cheking the spark plug, it happen 2 times a spark plug wire broke.

I would still take a look, I have repaired many broken plug wires without replacing them - not that I am recomending this, but perhaps that guy did the same.

If he replaced them someone would have recieved the bill.

Replacing the broken ends does not fix the wire which deteriates over time.

when the wire was broking he just put back the hummm socket at the end of the wire
he didnt changed the wire

I have a 93 GT and I get about 400-450km's per tank city driving. If your rpm is jumping between 500-1000rpms, it is known as "hunting". Your throttle position sensor (TPS) is likely bad or the idle air control (IAC) is dirty/bad. I would check the IAC first and give it a good cleaning. It is on the drivers side just behind the throttle body if you are looking into the engine compartment from the front. It has two wires wires going into a plastic body, and two screws holding it in. Disconnect the plug, take out the screws and slowly wiggle the IAC out. It will look like a cone on a shaft with a spring along the shaft. Clean the IAC with brake clean or throttle body cleaner. Before you go to put it back in, slightly rock the end back and forth with your thumb to compress the valve slightly so it is not damaged when you put it back in. If it will not compress or move out, the valve is likely shot and should be replaced. I suspect that is your problem, but if your wires are coming apart, I would suggest replacing the wires and plugs as well.

ok
ill take a look at this

thanks

check your vacum hoses near your air intake manifold.