Elvis If I may hazard a theory here, I would say that it all boils down to response time and integration. The ECU's (I just can't bring myself to call them "computers") are designed on old ideas using old components. They also don't communicate with each other. They simply chase inputs and don't have the response time to keep things stable when the engine is severely out of tune from fuel or ignition problems. I also believe these systems fight each other because they don't communicate. The idle ECU is only chasing RPM's without regard to emissions status and the Lambda ECU is trying to regulate emissions without regard to RPM'S. They don't care what each other is doing. Newer cars (I believe) are much more integrated in their control systems. Still...I wouldn't have it any other way. I enjoy trying to meet the conditions necessary to make all of these systems play nice with each other causing the engine run as it was designed. Notice I don't say "run better". I've seen engines that ran great, with good power, passing emissions and decent fuel economy but with half of the systems being bypassed. I want to have my cake and eat it too. Rich A. #5335 --- In dmcnews@xxxxxxxxxxxxxxx, "Elvis Nocita" <elvisnocita@xxxx> wrote: > > > And still - a good control loop can compensate any hunting of the idle, > especially the bad ones that let the idle vary with about 1Hz. > > There's absolutely no reason or explanation behind an idle speed hunting > between 900 and 1200rpm other than a badly designed control loop. > One cylinder firing better or worse won't affect the idle like that > at all, the other 5 will smooth it out ! >snip< To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/