NH911

I have a '99 996 with a tiptronic transmission. When the car's RPM's are around 1800, the needle will jump back and forth up to 2200 and back down to 1800. YOu can feel/hear the engine reving up and down when it does this.

I know I shouldn't be driving the car at that low an RPM but when I am in automatic mode and driving in traffic, I let the car do the work for me. Any thoughts on what might be causing this? It seems to have coincided with the 60K service where it wasn't doing it before I took it in but now it is.

Thanks ahead of time for your help.

djantlive

I would take the car back to where you got serviced. I suspect the plugs are not torqued tightly and you have a vacuum leak from there causing idle fluctuation.

gota911

With the symptoms you described, my first thought was a loose vacuum hose or leak, as djantlive stated.

nycebo

When warm, my car's idle fluctuates between 650 and 800 rpm in a slow rhythmic manner. Has anyone ever noticed this tendency or is it time for me to clean the MAF sensor and/or check the plugs?

Tool Pants

I call this hunting idle. http://www.renntech.org/forums/index...442&hl=hunting

We did clean out the car on this Box and a 996 at a work on cars day last year.

nycebo

Thanks Tool Pants.

NH911

The tech says that the transmission might be slipping and that is why I see the RPM's reving. He recommends starting with a transmission fluid flush and change. I find this hard to believe. The problem started when I had the 60K service done so it just makes more sense that it would be a vacuum leak or a plug not torqued correctly as indicated in an above post. If the transmission were slipping, why would it only do it at 1800 rpms? Thanks.

1999Porsche911

Unlikely transmission. What does your vacuum gauge read at idle and at 2000 rpm?

NH911

Tech spent an hour with the car and there are no codes reading on the computer. He took it for a drive when it was cold and said the transmission was slow and shifted hard. He somehow checked the fluid and it was low. I'll be getting complete transmission fluid flush and refill this week. He says this will fix the problem. It will run me about $350. Any of this make sense?