'86 911 engine revving question
Thread Starter
Three Wheelin'
Joined: Oct 2007
Posts: 1,911
Likes: 17
From: Ottawa, Ontario
'86 911 engine revving question
A strange thing happens when I am stuck in traffic. My engine idles at around 1k RPM, but sometimes, for no reason, it starts revving from 1k rpm to 1.1k rpm over and over again as if i were pushing on the gas pedal every second or so. If I rev the engine to 4k or 5k rpm it sometimes stops, but often it just starts again when the rpm's get back to idle. Anyone every hear of that or experience that before?
Burning Brakes
Joined: Mar 2002
Posts: 918
Likes: 1
From: Greensboro, NC
Yes, you can clean the ICV with isopropryl alcohol (or something similar), and make sure the "plunger" is moving freely inside when you shake it. When I cleaned mine sometime back, it did "help", but still wasn't 100% correct, and I ended up purchasing a new one form Pelicanparts after a few months. Idle is perfect now...hope this helps.
Keith
'88 CE coupe
ps: I'm not one for "throwing parts" at a problem, but the ICV is sort of like a DME relay imo...you're going to need one eventually, so I bit the bullet.
Keith
'88 CE coupe
ps: I'm not one for "throwing parts" at a problem, but the ICV is sort of like a DME relay imo...you're going to need one eventually, so I bit the bullet.
Burning Brakes
Joined: Sep 2002
Posts: 814
Likes: 3
From: Southern California
Before changing the ICV, be sure the mixture is adjusted properly. A bad mixture can cause the engine to surge. If that doesn't solve the problem, the next thing you should try is the ICV.
Legacy Flounder
Rennlist Member
Rennlist Member
Joined: Nov 2004
Posts: 3,439
Likes: 0
From: Cumberland, RI
It may not be the idle control valve. Mine does this, I replaced the valve, same thing.
My car's running a Weltmeister Chip too, and the running rich thing is a possibility - folks have told me that up-converting the DME to a later year chip pinout & increasing the memory (replacing the chip) can help this condition... Helloooooo Steve Wong.
FYI... The generic (Wells) valve I got from Autozone at a fraction of the price turned out to be a Bosch.
My car's running a Weltmeister Chip too, and the running rich thing is a possibility - folks have told me that up-converting the DME to a later year chip pinout & increasing the memory (replacing the chip) can help this condition... Helloooooo Steve Wong.
FYI... The generic (Wells) valve I got from Autozone at a fraction of the price turned out to be a Bosch.
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Racer
Joined: Apr 2006
Posts: 323
Likes: 6
From: Whittier, CA
My 88 Carrera had a similar symptom about a week ago...
So yesterday I decided to clean the ICV as mentioned. It also felt like the motor was not running smoothly when progressing from part throttle down to idle.
I used isopropyl alcohol then carb cleaner. When I started it up after cleaning, the idle jumping from 1K to 2K then back to 1K multiple times. I had confidence that it was just a temporary condition from the rich carb cleaner mixture.
Sure enough when I drove it today, it cured the un-smooth symptoms and the idle is perfect.
Thanks Keith et al.
I used isopropyl alcohol then carb cleaner. When I started it up after cleaning, the idle jumping from 1K to 2K then back to 1K multiple times. I had confidence that it was just a temporary condition from the rich carb cleaner mixture.
Sure enough when I drove it today, it cured the un-smooth symptoms and the idle is perfect.
Thanks Keith et al.
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