Re: Lack of Boost, '88 5ktq

["Scott Mo." <scottmo@teleport.com>]

>Russ Southerlin wrote:
>Sound like you simply have a tired wastegate spring if all other engine >functions are O.K.
> I had a same thing when I first got my car a year ago.It turned out to
> be nothing more than a tired (stock) wastegate spring.  I went the the
> local Ace Hardware and found a heavy duty spring that fit inside the
> diameter of the stock spring and then cut it to length by trial and
> error was able to get consistently 1.4 bar of boost.  

If the ECU boost control system and components are working correctly,
the ECU will add pressure on top of the Waste Gate (WG) diaphram using
the WG solenoid and will overcome a weak WG spring. Normally if the
boost is only controlled by the stock WG spring with the upper WG hose
removed, you will get 1.2-1.3 bar. With the ECU assisting, the boost
should be ~1.4 bar as is set by the boost map in the ECU EPROM. The
boost map values change slightly at different engine RPM values. 

Putting in a stiffer WG spring is only masking a problem or fault in the
boost control system. A defective throttle switch is a likely culprit
but, for details on things to check out which can cause low boost, check
out the ABC's of Running High Boost" at

http://www.teleport.com/~scottmo/boost.html

 I suspect that there are many 1986-90 5000/200TQ's driving around with
low boost due to faulty components in the ECU system.
HTH
-- 
Scott Mo.
1989 200TQ
http://www.teleport.com/~scottmo