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Re: CIS: Really hard starting only at ski resorts?? Posted by Dana [Email] (#2822) [Profile/Gallery] (more from Dana) on Tue, 16 Jan 2001 20:29:03 In Reply to: CIS: Really hard starting only at ski resorts??, Todd 83-900T, Tue, 16 Jan 2001 09:34:55 Members do not see ads below this line. - Help Keep This Site Online - Signup |
We normally don't think about it much but the orginal CIS fuel/air mixture screw adjustment position can not remain the same over many years. This is because one does get wear on the modulating valve (leaks thru a bit more), the tip of the screw adjustment wears....etc. etc... Manual wants you to think that the closed loop control system will automatically adjust the ratio of the modulating valve on/off timing to allow for this long term wear...but I believe that eventually that under driving conditions the modulating valve on/off ratio may move closer to the limit of the control range of adjustment. As you move the car to an extreme change such as elevation, then this already marginal control is not enough.
As already mentioned below, I would recommend you start up the car, warm it up and take a look at pulse ratio...to see if it is still 50/50% modulating cycle under normal idling warm conditions. If it is not..and you have no air leaks, etc....it may be time to try a readjustment of the fuel enrichment screw (under the metal plug on the fuel distributor). I would suggest that you make sure the back pressure from the warmup regulator is within the normal cold start/warm run values first. I have found the warmup regulator can be cleaned by disassembly. It made a big difference on the 85 CIS. Then you can adjust the distributor fuel enrichment screw to give you a 50/50 modulating valve operation under normal warm idle. This will require a meter to read the duty cycle of the modulating valve.
But between the fuel pressure gauge kit for CIS from WC Whitney and the duty cycle meter...you REALLY have the tools to do the job right. The O2 sensor will end up being controlled at .5VDC all the time...the real point is it should be doing this with a 50/50% timing of the modulating valve under normal warm idle....thus there is control room from approx 20/70 to 75/25 for variations of climate changes.
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