View Full Version : fluctuating tach??

06-06-2002, 11:14 AM
I just got done cleaning out my throttle body. It idled really fast ofter I was done so I adjusted a few things and now it is back to normal idling speed. The problem now is that in P or N the tach will fluctuate between 1k and 1.5 k. It will drop to 1k and then the engine will rev up to 1.5 k then drop back to 1k and then rev back up to 1.5k repeatedly. What can be causing this????

any help please!!!

Thanks y'all

Oh yeah, post 101 BABY:super:

06-06-2002, 03:17 PM
bad throttle body

06-06-2002, 03:19 PM
when i had that problem i got a throttle body from a wrecking yard. i cleaned it up and i havent had the problem sence.

06-09-2002, 09:03 AM
check your drive belts, see if they are damaged. How is your EGR valve? u did not loosen any vacuum lines in the process or forgot to put em back in did you? u did not see any dust get into the throttle body and into the manifold did it? how is your gasket? did u mess with the timing? if everything seems right, then it should not do it. the fluctuation seems like a loose idle screw or a leaking/loose/unhooked vacuum line.

06-09-2002, 11:27 AM
look under the sit at the computer, may be some sensor burn up or something like that.
look see if the light is blinking.

06-09-2002, 01:02 PM
It'S usually the Intake air control valve. It's located in front on the intake manifold and has a yellowish connector to it.

unplug the connector and see if the problem goes away

06-09-2002, 05:40 PM
No, no no.. I know what exactly is going on! Happened to me when I cleaned my TB. IT's the Fast Idle Valve (or something like that). I believe I talked about this a while back.. it's over here: http://www.3geez.com/showthread.php?s=&postid=2782#post2782

Here's a picture of what I'm talking about:

Carrotman might be right on that yellow 'thing'. If you do what he says it resets the system to your current conditions (at least that's what I've read)

06-09-2002, 08:16 PM
Hey, thanks for the responses people. I will try some of the quick fixes first to see it they help. If not, I will look into getting a different Throttle body.

We'll have to wait and see what happens.

Thanks y'all


06-10-2002, 10:18 PM
The picture by dosh8er is correct. It's called the Cold Start Valve... just unscrew one screw and loosen the other and swing the cover out of the way. Next take a big screwdriver and tighten the valve in. It's weird looking, but the screwdriver will catch one of the edges of the valve. Tighten the cover back on and that should get rid of the hunting engine speed.


02-01-2004, 11:24 AM
I had the same problem with my 89. I took it to a friend that is a mechanic and he said that the TPS (Throttle Position Sensor) could be the cause. The reason is that the car is trying to find the correct throttle position to idle at if the sensor is faulty then it usually searches within this range of 1000- 2000 rpm. Replace The TPS, most likely this is the cause.

02-12-2004, 08:36 PM
yeah, i have that problem sometimes too, try unplugging the tps and see if it still does it, if the thing is unplugged the engine runs of of default values which wouldnt have an error in them (it would run like crap however :) )