How to... TPS idle...
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
How to... TPS idle...
I'm in process to set the idle and the TPS on my 90 auto. I read the procedure on the C4 tech tips. (good explained)
"...with the IAC disconnected turn the adj. screw since you reach the 450 rpm readind in the tach....."
My tach is out abuot 200 rpm at idle!!!
My aftermarket tach read (with the IAC connected in Drive) 560 rpm.
The standard tach says 750 770 rpm.
(at 4700 rpm the stock tach says 6500!!!)
I have to follow the aftermarket tack or the stock inaccurate tach??
...And for setting the base timing?? I have to follow the aftermarket tach or the stock one??
-Beppe-
"...with the IAC disconnected turn the adj. screw since you reach the 450 rpm readind in the tach....."
My tach is out abuot 200 rpm at idle!!!
My aftermarket tach read (with the IAC connected in Drive) 560 rpm.
The standard tach says 750 770 rpm.
(at 4700 rpm the stock tach says 6500!!!)
I have to follow the aftermarket tack or the stock inaccurate tach??
...And for setting the base timing?? I have to follow the aftermarket tach or the stock one??
-Beppe-
Team Owner
Joined: Jan 2003
Posts: 20,326
Likes: 252
From: Summerland B.C. Canada
Re: How to... TPS idle... (conv90)
Back off the idle screw till the engine almost dies due to low idle speed. Now look at each tach and use the one thats reads closest to 450. Continue to adjust idle till that one reads 450. Chances are the aftermarket tach is correct. Good Luck !!! :cheers:
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
Re: How to... TPS idle... (AGENT 86)
I' pretty sure the aftermarket tach is absolutely correct...
My only concern is the Factory (GM) has all 'data' set by the stock tach....
-....Others suggestions???
-Thanks-
Beppe
[Modified by conv90, 7:35 PM 5/7/2003]
My only concern is the Factory (GM) has all 'data' set by the stock tach....
-....Others suggestions???
-Thanks-
Beppe
[Modified by conv90, 7:35 PM 5/7/2003]
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
Re: How to... TPS idle... (conv90)
The value you see on the factory gauge has little to do with what the computer sees as the real engine speed. As stated above, just keep backing out the screw until the engine almost dies. I know that my 90's tach is way off - if I used to calculate my rear ratio I get 4.11s or so and know that is not right. YMMV
I think the 450 number is more or less arbitrary. If I am wrong please correct me.
Dale
:cheers:
I think the 450 number is more or less arbitrary. If I am wrong please correct me.
Dale
:cheers:
