Idle problems often traced to air leak
Advertisement
Read this article for free:
or
Already have an account? Log in here »
To continue reading, please subscribe:
Monthly Digital Subscription
$0 for the first 4 weeks*
- Enjoy unlimited reading on winnipegfreepress.com
- Read the E-Edition, our digital replica newspaper
- Access News Break, our award-winning app
- Play interactive puzzles
*No charge for 4 weeks then price increases to the regular rate of $19.95 plus GST every four weeks. Offer available to new and qualified returning subscribers only. Cancel any time.
Monthly Digital Subscription
$4.99/week*
- Enjoy unlimited reading on winnipegfreepress.com
- Read the E-Edition, our digital replica newspaper
- Access News Break, our award-winning app
- Play interactive puzzles
*Billed as $19.95 plus GST every four weeks. Cancel any time.
To continue reading, please subscribe:
Add Free Press access to your Brandon Sun subscription for only an additional
$1 for the first 4 weeks*
*Your next subscription payment will increase by $1.00 and you will be charged $16.99 plus GST for four weeks. After four weeks, your payment will increase to $23.99 plus GST every four weeks.
Read unlimited articles for free today:
or
Already have an account? Log in here »
Hey there, time traveller!
This article was published 03/07/2009 (6031 days ago), so information in it may no longer be current.
QUESTION: I have a 1987 Chev Silverado, 350 engine with throttle body fuel injection. With the transmission in gear and stopped, it will idle for a few seconds and then stall. If I adjust the idle screw up it solves the problem, but the idle speed is too high. When I come to a stop light I just slide it in to neutral which is a bother or keep the accelerator pedal depressed a bit, which is not good for the transmission. I have had it to two or three garages but they were unable to find the problem. Any ideas?
ANSWER: Idle problems on these GM truck throttle body fuel injection systems could often be traced back to an air leak at the throttle body base gasket. If the throttle body mounting bolts are not torqued properly, the base gasket can be sucked in causing the air leak. Typically this happens slowly over an extended time period.
The fuel injection computer for this system controls idle speed with the idle speed control motor but does not have the ability to adapt to air leaks. Instead, it will control idle speed based on its program first and then try to control it after it sees rpm change. Usually this doesn’t occur fast enough and the engine either idles too fast or stalls.
A common (and incorrect) repair was to turn out the throttle plate stop screw to compensate for the air leak. This prevented the idle speed control from working properly, so engine stalls were then common. The proper repair is to fix the air leak. Then set the throttle stop screw with the air passage for the idle speed control motor blocked off. Initial RPM setting should be in the 600 to 625 range. With the idle speed control motor passage unblocked, the computer can now control the idle speed correctly and your truck should work properly.
Jim Kerr is an experienced mechanic, instructor of automotive technology, freelance journalist and member of the Automobile Journalists’ Association of Canada.
kerr.jim@sasktel.net