Scott M.

86 951 90k miles: My idle will tach up to ~2k rpms occassionally, sometimes in the mid 1k's. Sometimes it comes back to normal...

Idle control valve or TPS??

buzzsaw

A buddy of mine had the same problem and said it was a vacuum leak issue. Apparently, he pulled the intake off and found lots of cracked/crispy hoses. Replacing/fixing them cured it.

Rip It

tps is easy, just unplug it and see what happens

jerome951

Likely not the idle control/stabilizer valve. It basically only kicks in when the engine is cold or when the AC is on. I don't think it can add enough air to raise the idle as much as you are seeing.

mclarenno9

Check your idle screw on the throttle body. I had the same problem and I noticed the screw was turned real far out. I turned it almost all the way down and stopped the problem all together.

95Juan

i have the same problem, i'm going to get my vacuum hoses changed out this week, so i'll let everyone know how that goes.

Scott M.

The odd part is that it is infrequent. I've seen the idle screw issue before and it was a constant high idle.
I notice some grime at the cover of the TPS, I'll pull it to see if it is nasty inside...

95Juan

yeah, 90% of the time, i idle perfectly, then i go up to 1k, then if i drive around for a while, every now and then it'll get stuck at 1.5-2k and then eventually drop down. i checked my tps and my idle screw deal, but i think it's vacuum lines....since i'm sure they're almost 20 years old.

951fan

I have been having the same problem. For some reason when I gave the ISV a good wrap it would kick the idle back down. I'm currently replacing the ISC and updating the entire vacuum system including the cycling valve delete. My cycling valve did not have one solid connection to it. That should certainly help things!

heybiff

And it's really starting to bug me. It only seems to happen after a lot of driving and combined with my rattling cat is VERY annoying.

I replaced my vac lines during the summer, and my idle screw is aactually sealed with epoxy ( thanks PO). I've contemplated disconnecting the ISV to see whatthat does. My ISV was replaced in the spring BTW, but I'm willing to accept it's bad.

Heybiff

RK951

what is the ideal idle for a 951?

jerome951

factory spec is 850 +-50

Chipster

I had the same problem a couple years ago. I replaced all the vacuum lines I could get to with the Lindsey kit. As I was doing so, I discovered the vac line hidden under the throttle body was off. I put a small zip-tie on it to make sure it didn't pop off again. Check your Blow-off valve while you're at it. If it's still the original, it needs changed. Take it off and try to blow through it. If you can, you need a new one.

Also make sure the TPS is set correctly. Open the hood and use your finger to slowly push the throttle valve off idle (with the engine off). You should here a small "click" just as it starts to move. If you don't hear ther "click" adjust the TPS (using the set screws) until you do.

This should solve the high idle problems - it worked for me.

If all else fails, you may need to check the fault codes. This is a whole other process and you need a fault code reader. I have a home-made reader that works great.

Hope this helps