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Re: 86 5kCSQ jerks when deacclerated


> I saw another post on the decel shutoff valve ... I'e never run into
> that one, but you could test to see if it was happening in your case by
> not completely removing your foot from the throttle.  

	It only happens when I removed the foot completely off the 

> The decel bypass
> is only enabled if the RPMs are above a certain value and the Idle
> Switch is closed.  

	The normal scenario for the jerk is while I am going around 
	20MPH, in 2nd gear, bar about 0.4 to 0.7, and if I take off 
	the foot completely. 
	My car idles around 1250 RPM, I am not sure if it is normal.
	I have ordered the service manual, and will look into this.
	By the way what is decal bypass?

> My thoughts were that the effect might be due to a
> high effective compression since you are on boost. 

	Excuse my ignorance on turbo, but if you mean by boost is 
	that the bar is 1.0 or higher, then I am not on boost.

> This would be more
> likely to be true if you quickly went from full throttle acceleration to
> foot off the gas.  

	Oh'  you are from San Jose. The scenario I am describing is when 
	at 6:00 PM you are going east on 237 in the right most lane to 
	take 880 north. If you are familiar with that area durring the 
	evening commute hours, you can imagine what a full boost will do. 

> Normally the turbo engine isn't great for engine
> braking due to the lower compression, but you can get a big spike of
> deceleration when the turbo is angry ... I don't think the '86 has the
> idle dashpot, so it is also possible for you to get a backpressure spike
> in the turbo and t\intercooler when the throttle is closed under high
> boost as well.  I don't know whether or not this will increase engine
> braking though ...
> HTH!
> Steve Buchholz
> San Jose, CA (USA)
> > ----------
> > 	Summary of the problem would be 
> > 	"Is hard engine braking normal to this car"

	Fremont, CA (USA)
	86 5kcsq