high rpm's

[bpgreer]

Well...The good news, is that my car is up and running. Timed, valves adjusted, new tires, etc. Bad news is that it is now remaining at high rpm's once I have been driving. It stays at 2000-2500 rpms when I am not pressing the accelerator. I'm not sure exactly what to think. I also recently replaced all of the vacuum lines. Any thoughts?

Brian

[SGB]

Underwear gnomes came in the middle of the night and messed with my accel cable linkage (the slack- or lack of it...) while I was doing my last valve adjust. After extensive time with feelers and TDC notches, I fired up and "RRRRR" revs zoomed up to 3k before I shut off. Actually, the car ran so much better after setting valves that the previous throttle cable setting was too tight. Check that before you go tearing things apart....

[Bleyseng]

Odds are you have hooked up the vacuum lines wrong and you have a vacuum leak that is causing the high idle.
Geoff

[bpgreer]

I agree that it is most likely a vacuum problem. I will double check all the lines. Are there any other common places for vacuum leaks other than the lines? BTW, my valves were all correct w/ the exception of #3 intake which was .002 loose.

The strange thing is that it was idling fine until it was on the road for a while (10min maybe).

[Dave at Pelican Parts]

Other places for leaks: The intake boots between the plenum and the intake runner pipes. Injector seals. Intake runner to head gaskets. Throttle body gaskets. The seam around the edge of the plenum. The top and bottom of the reinforcements inside the plenum. The AAR not closing all the way. The Decel Valve not closing all the way. The PCV.

--DD

[SteveStromberg]

Oring on oil Cap?

[Dave at Pelican Parts]

Hmm, good suggestion! I don't think it would contribute to high idle in a 73 2.0, though--the air in the crankcase has to go through the PCV to get into the manifold.

Definitely a suspect on the 1.8s, though!

--DD

[bpgreer]

I no longer think it's a vacuum problem. When it acts up, if I quickly press and release accelerator, it goes back to normal. I think the accelortaer cable is the culprit. Has anyone heard of that?

[Scooter311]

Try disconnecting it, have someone fire it up, and goose the throttle by hand - oh wait, can you do that on FI cars?
Nevermind me...

[Bleyseng]

Could be that the accel cable is wrapped around the clutch cable inside the tunnel. BTDT!

Geoff

[Dave at Pelican Parts]

Yup. Could also be that the throttle plate is hanging up in the throttle body bore. You can indeed goose the throttle by hand; all you do is grab the bellcrank that the throttle cable hooks onto and twist it.

You can remove the cable from the bellcrank to get the whole cable/pedal part of the system out of the loop; if it still hangs up then you know those aren't contributing.

Another thing to think about--advanced timing will raise your idle RPMs. Perhaps you have a vacuum retard that is sticking? Or the centrifugal advance is?

--DD

[bpgreer]

It was the accel cable. Replaced it last night and the problem is gone!!! Very easy replacement to boot. Of course now the car is "bucking" slightly at lower rpm's when I'm driving. It seems to get worse the longer it's on the road. Anyone had similar problem? It's not horrible, but it's definately noticeable. Hopefully this will be the last big "hiccup" in the system.

Brian

[Bleyseng]

If its at about 2500-3000 its the TPS.

Geoff

[bpgreer]

Could it be mis-adjusted? Or do you think it's bad? Thanks.

Brian

[silver2.0]

either/or
I replaced mine, thought it was bad, and it felt the same. Turns out you have to adjust them correctly. Go figure. I bought mine off e-bay for cheap. (cheap for a porsche, anyway)

[bpgreer]

It is definately the most noticeable around 2500-3000 rpms. It also gets more pronounced the longer it's driven. Any more thoughts???? I set the tps with an ohm-meter as per the pp tech article a week ago. I guess I could give it another shot. The car only has 62000 miles on it. I wouldn't think that part would wear out that quickly.

[Bleyseng]

They wear out fairly fast, say 15-20,000 miles.

[bpgreer]

I tried unplugging the tps and there was no difference. Any further thoughts on cause? If I accelortate fast, it's hardly if at all noticeable.