Revs up dan down

i have a 1996 ford taurus lx 3.0 v6 dohc…everytime i start the car up it rev up to about 1500 rpm then goes back down to 800 rpm then goes back up…i will do that for about 5 mins till car werms up some…here is what i replace so far…new coil’‘new plugs and wires.tps’‘maf’iacv.pcv’…i clean thorrybody out good…new air filter…and there is no check engine light…i did take it to 5 mechanic shop and they can’t fine anything wrong with car so i hope you guys can help me out…

You have a vacuum leak that will close up when warm. This is typical of intake manifold gaskets gone bad. However, the mechanics can’t catch it unless the car is stone cold. Warm, and there is no leak.

ok ill take a look at that thanks for your help

Smoke test when engine is cold should find it.

i leave my car at shop last night so they could do smoke test…the shop called me about hour ago and said there was no air leaks …so now what do i do know im just so lost right know

give you guys a update…the shop called a said even thou there is no check engine light on he said he pull up code p0171 and p0174

If it has been confirmed that there are no vacuum leaks from either vacuum hoses or the intake manifold, then the likely culprit is the Mass Air Flow sensor (MAF). A bad MAF can trigger both of those codes.

even thou there is no code MAF it still cud be bad…i do know when they unplug the MAf sensor the car idle when up then they plug it back in then idle went back down to 800 rpms

I agree with the others. A faulty and/or contaminated MAF sensor can cause lean codes P0171 and P0174 and a bad idle

well, all of that and intake manifold leaks. I get that the smoke test was done, but are you sure it was done cold?

they told me wen he done the smoke test the car was cold and i was not there to see it for sure…i will take it to someone else and have them to look at it agin…i think ill took it to at lest 7 shop and no one can find what’s wrong with my car…i just want to thank you guys very much for your help because i don’t know about car that much

how can i check maf sensor at home to see if it’s working right ?

This might help.

ok guys i thank i find it…i went outside to start the car up before i started the car up i unplug MAF and car run alot better…when the car was running i plug it back in and idle started to go back up and down agin. so what do you guys thank about that?


Your MAF is defective

No doubt about it whatsoever

When you ran the car with the MAF unplugged, the PCM used default values

If the car runs better with a sensor unplugged, the sensor . . . or the wiring circuit . . . is defective

Congratulations on diagnosing the problem!

Please let us know when the car’s running normally with the new MAF installed

ok guys i replace MAF sensor and car runs alot better…i just like to thank you guys for your help…and now my power steering Pressure line is linking where it goes to pump…so how do i replace that line and i got new pressure line…1996 ford taurus lx 3.0 v6 dohc

The line usually connects to the power steering pump at one end, the steering rack at the other end, and maybe a retaining clip or two or three along the hose run.

how hard is it to remove that line and been looking online and i can’t find anything how to remove it

The fittings should just be a standard metric hex head size. After they’ve been on there that long they can get a little stubborn, and access is often any fun. The best option would be if you have a flare nut wrench of the proper size. Other than that any old wrench can be tried. You just thread out the old, route and thread in the new. If the access is really bad you might need things like socket extensions and crow’s feet ends for them

i replace MAF senser and now i get code p0171 and p0174