SiriusBlack Posted September 15, 2019 Share Posted September 15, 2019 Alright here it goes. I have a 1986 Subaru BRAT GL. It has some incredibly irritating idle issues. It will idle fine just after start up and around town, about 700 RPM just like the factory manual says is the sweet spot. However after getting up to highway speed you step on the clutch to shift from third to forth gear, and instead of the engine speed dropping it shoots up to nearly 5000 RPM. If you need to slow down to turn off the highway, and you step on the clutch it will "idle" at around the 5000 RPM point again. It comes and goes, I can make a trip from point A to point B with it having this issue. Then when I make the return trip to town and have to go to lower speeds, sometimes it will begin idling correctly for no apparent reason. We have checked for vacuum leaks and believe we have eliminated all the lines as possible cause. Whoever worked on it last had replaced the high and low speed lines without putting in the required orfices, so we fixed that with high hopes and got nothing. I have done lots of research and have several other things to try. Such as cleaning the EGR valve, doing a complete rebuild as I know it likely needs it, and replacing the the whole entire Hitachi if when I pull it again the throttle shaft bushings are shot. I will keep experimenting, but any advice could help. As for the people that will likely insist the only solution is to chuck the Hitachi in a bin and get a Weber, I might do that in the future but I want to keep this car as factory as I can. Any help is appreciated. Quote Link to comment Share on other sites More sharing options...
DaveT Posted September 15, 2019 Share Posted September 15, 2019 (edited) I would be looking for something hanging up the throttle. Weak spring, sticky cable, binding throttle shaft. Stuff like that. Maybe the choke & high idle mechanism. Vacuum leaks and egr can cause problems, but I have never had or read of one causing idle to go to 5000rpm or even close. Those usually cause crummy idle, poor performance. Edited September 15, 2019 by DaveT Quote Link to comment Share on other sites More sharing options...
Steptoe Posted September 15, 2019 Share Posted September 15, 2019 It is not gonna rev at that speed unless the throttle is getting open or a bitch of an air leak. Sticking throttle mech, and check cable condition, floor mats , PCV and booster hose and function Quote Link to comment Share on other sites More sharing options...
SiriusBlack Posted July 5, 2020 Author Share Posted July 5, 2020 Well last winter after rebuilding the Hitachi twice, I got rid of the 5000RPM idle issue but then I ended up with really poor idle. So I finally went with the Weber and it runs like a dream, I changed the general conversion a little to make sure it isn't permanent. I have some small idle issues, but I am contributing those to the fact that my ignition system is kinda jurry rigged at the moment. As soon as I can afford the proper distributor I'm hopeful those will go away as well. 1 Quote Link to comment Share on other sites More sharing options...
Step-a-toe Posted July 5, 2020 Share Posted July 5, 2020 Good stuff New Weber or just as cruddy looking as your worn out and fiddled with Hitachi? Quote Link to comment Share on other sites More sharing options...
SiriusBlack Posted July 6, 2020 Author Share Posted July 6, 2020 Brand new, with a chrome air filter housing and everything :). Quote Link to comment Share on other sites More sharing options...
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