I have a 97 taurus vulcan at 120k miles. Rpm will randomly jump to anywhere between 1000 and 2000, usually it jumps to about 1600 but it can be higher or lower. This is all while it's in park. It'll jump from regular of 800 to 900 to the above mentioned. In drive, if I let off the brake from a stop it'll sit at about 1200 without hitting the gas pedal. Now before anyone says IAC, I'm not completely ruling that out tho either, the iac in it is about a year and a half old. It is a motorcraft one, the electrical connector is about 2 months old (I replaced this because the latching part of it had snapped off). After initial replacement of the iac the problem had disappeared for about a year, plug was broken entire time, then the problem returned. After i replaced plug, the problem was gone for about a week. And now more recently I took the sensor off and cleaned it, replaced gasket, and cleaned the MAF. Problem was gone for a day and then returned. Lol it's driving me crazy. To temporarily cure the problem I'll go out and unplug then replug the iac and it'll return to normal for anywhere from 5 minutes to an hour. This used to only happen about once a day but now it's sporadic, anywhere from once a day to 10 times. Also worth mentioning, if I just let it go, the car will eventually unrev and go back to normal.
It seems this has gotten worse since it started getting colder out, also now that I think about it, this doesn't seem to start until car has reached operating temperature. I've looked for vacuum leaks but I haven't really tested for them other than watching fuel trims which stay close to zero cold or hot engine.
Anyways, why I'm wondering tps. Today I was watching values on my scan tool. At regular idle, tps is about 16 percent, which I've seen as normal elsewhere in the forum. But once it decides to rev, tps jumps to 21 percent. Long term fuel trim then jumps to about +8 on both banks, short term becomes sporadic jumping between -5 and +5. So I then unplugged iac while watching tps percent, it drops back to 16 percent with iac unplugged and then stays at 16 once plugged back in.
Another reason I think tps, when engine is hot and I start it. Occasionally it will instantly sputter and die unless I hit the gas and hold it at about 2000 rpm for about 10 or 15 seconds.
Sorry for the long post, this is my first post and I figured the more information the better.
I'm currently replacing pcv valve and grommet. I'ma see if that helps any, then if not, I'm considering using seafoam spray to clean throttle body and whatever else the spray reaches to see what happens.
Thanks for the help.
It seems this has gotten worse since it started getting colder out, also now that I think about it, this doesn't seem to start until car has reached operating temperature. I've looked for vacuum leaks but I haven't really tested for them other than watching fuel trims which stay close to zero cold or hot engine.
Anyways, why I'm wondering tps. Today I was watching values on my scan tool. At regular idle, tps is about 16 percent, which I've seen as normal elsewhere in the forum. But once it decides to rev, tps jumps to 21 percent. Long term fuel trim then jumps to about +8 on both banks, short term becomes sporadic jumping between -5 and +5. So I then unplugged iac while watching tps percent, it drops back to 16 percent with iac unplugged and then stays at 16 once plugged back in.
Another reason I think tps, when engine is hot and I start it. Occasionally it will instantly sputter and die unless I hit the gas and hold it at about 2000 rpm for about 10 or 15 seconds.
Sorry for the long post, this is my first post and I figured the more information the better.
I'm currently replacing pcv valve and grommet. I'ma see if that helps any, then if not, I'm considering using seafoam spray to clean throttle body and whatever else the spray reaches to see what happens.
Thanks for the help.
