FAQ Frequenly Asked Technical Questions. This section is read only, and posts are made by the staff. If you have something to contribute contact any moderator.

rough idle with codes 21, 22, 26, 27, or 30 - TPS ISC

  #1  
Old 02-04-2008, 08:11 AM
stomper's Avatar
Tech Certified Members
Thread Starter
Join Date: Jun 2007
Posts: 2,701
Default rough idle with codes 21, 22, 26, 27, or 30 - TPS ISC


TPS & ISC replacement/adjustment
1980's cars

If the diagnostics are run after a Service Soon error is shown, and errors relating to the Throttle Position Sensor (TPS) and/or Idle Speed Control (ISC) are 21, 22, 26, 27and/or 30, it is likely that the TPS is worn.

A worn TPS will give an intermittent throttle position readout to the ECM, and can cause the idle speed to fluctuate and cause the above errors. The TPS is used to send the throttle position to the ECM, indicating to the computer the angle of throttle. It senses 0-90 degrees of throttle angle.

The ISC is controlled by the ECM and adjusts the idle speed dynamically according to load when the engine is at idle.

The airconditioning compressor cycling or moving the gear selector from Park/Neutral to Forward and Reverse positions will change the load on the engine, which the ISC compensates for. If either the TPS or ISC are replaced, they need to be adjusted together.

Factory Manual section 6D3-12

http://www.ht4100.com/Diags/HT4100ISC.pdf


 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
joez34
Tires and Wheels
1
01-10-2009 04:48 PM
2001slswhite
General Tech
1
05-21-2008 10:04 PM
touringsedan
General Tech
10
04-01-2008 07:10 PM
Stealth
FAQ
0
11-19-2007 11:01 PM
Adrian12
Cadillac Deville
4
09-03-2006 09:07 AM


Thread Tools
Search this Thread
Quick Reply: rough idle with codes 21, 22, 26, 27, or 30 - TPS ISC


Advertising
Featured Sponsors
Vendor Directory

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.