what would cause slight jumps in rpm?

[zixxer]

fully tuned up, new plugs, wires, cap&rotor,


is it possible that an alternator going out could cause this? It happens only at idle, and the engine idles around 700 rpm, but will jump up to 900 or 1k every 5 or 6 seconds. (this is with no a/c, no fans coming on, etc.)

 

[djNickb]

bad gas?

 

[amcdonald]

I think you might have herpes. You should probably buy one of the 'el cucaracha' horns.

 

[notfred]

About a million things, of which 750,000 are various different electrical connections under the hood.

 

[DurocShark]

Don't forget vacuum leaks.

 

[Ness]

Do you hear any differences in engine noise when it jumps or is it just the guage?

and Roger will eat your face if you don't post make, model and year.

 

[NikPreviousAcct]

It's a sign that El Chupacabra is about to attack!

 

[zixxer]

Originally posted by: ness1469
Do you hear any differences in engine noise when it jumps or is it just the guage?

i hear it..

it's almost like the a/c compressor is coming on (where the engine compensates for the load by revving a little higher).. but it's not.

 

[opticalmace]

your foot

 

[Quixfire]

Nitrous

 

[Howard]

Your heart's pulsing throughput is pushing your foot forward. Check about getting a restrictor plate.

EDIT: I hear McDonald's sells them.

 

[AMCRambler]

Doesn't have to be the ac compressor turning on, it could be an electrical device like a radiator fan that turns on and is putting more load on the alternator so the engine revs up to counteract. My Honda used to do that when the radiator fans turned on. Might also be a problem with your fuel pump relay. If it's not working it could be making the pump run erratically sending spurts of gas through to the injectors or something along those lines. Those are my two guesses. What do we win if we're right?

 

[zixxer]

Originally posted by: AMCRambler
Doesn't have to be the ac compressor turning on, it could be an electrical device like a radiator fan that turns on and is putting more load on the alternator so the engine revs up to counteract. My Honda used to do that when the radiator fans turned on. Might also be a problem with your fuel pump relay. If it's not working it could be making the pump run erratically sending spurts of gas through to the injectors or something along those lines. Those are my two guesses. What do we win if we're right?

lol


I think it has to do with my stereo system. I have a 760 watt amp w/ a 1 farad cap but I think my alternator *might* be going out.

 

[Ness]

Why don't you try unhooking the stereo for a little bit and see if that makes a difference.

 

[OZEE]

Have you changed the alternator fluid recently??? Or how 'bout the muffler bearings? Could be that too.

 

[ThisIsMatt]

It's most likely not your alternator.

 

[iamwiz82]

does it jump up and slow go down or jump up and jump down?