Ok, first of, i have a 91 N/A...

When cold, if i start the car, first it revs up to 3 grand for a few seconds like normal, and then it settles down to a high idle, around 1500 a few seconds later....

It sits there for a little bit (30 seconds, maybe less), and then starts vibrating periodicly from around 1200 to 700 rpm.... it does this in a regular fashion, up down up down up down, and it seems to be at a constant "tempo"

then, after the secondary throttle plates move back (thermowax thing or something), it settles on the fast idle, around 1200... and then just stays there

Also, i tried reving the engine up and i held it at a constant 3500 rpm, and listened to the exaust pops... i got a pop every second... looked at my watch, and every time the second hand moved it poped, i watched it for about a minute and it never missed a beat.

I'm thinking it might be the 02 sensor, but does that have anything to do with idle (im thinking it might be the sensor, because it sounds like an ocillation from the cpu, (every second... something digital things like to do), but i have no idea...

Has anyone ever seen anything like this... any ideas?

 

Many have these types of problems.

Sounds like a vac leak to me...i had a similar situation turned out to be a bad ACV

But just to be sure do the following first.
Search for instructions, there are many threads

Check/Set TPS
Test BPAV (BAC)
Test ACV
Check for Vacuum Leaks

 

Many have these types of problems.

Sounds like a vac leak to me...i had a similar situation turned out to be a bad ACV

But just to be sure do the following first.
Search for instructions, there are many threads

Check/Set TPS
Test BPAV (BAC)
Test ACV
Check for Vacuum Leaks

 

vac leak or sticky sensors. i played with all my sensors, moving them back and forth, unhooking the connections and rehooking them. now i have a nice pretty 750 idle.

 

ok, im just gonna go get my car inspected... hey its free anyway, and if i pass then i can worry about this later ;-)

but keep the responses coming, cuz i really want to fix this

 

damn line, was like 20 cars long... maybe i should make an appointment

anyway, my idle after driving around for like 30 minutes finaly settled down to around 700.... any ideas what that would mean?

 

ok, also, i notice that after ive been driving for a while and the engine is nice and warm, if it goes and settles on an above 1000 rpm idle, i can turn my lights on, and when i do the idle drops to 700, and then if i turn the lights off it stays there.... has anyone had that... is that the BAC valve?

 

Just try setting your tps and idle speed with the initial set connector see if it happens after that...

The BAC adjusts air for electrical loads so it could be sticking... there are tests for that lots of write ups you just have just got to search for them

like i said TPS, BAC, ACV, vac lines