Guest darrenhopper Posted January 16, 2013 Share Posted January 16, 2013 Morning all, I've been a while trying to track down an issue on my project car & cannot find anyone with a similar problem on this forum or elsewhere. What it is doing when started is as follows: - Start after a couple of turns and idle smoothly at about 2900rpm - Roughly half a minute after startup the idle (still smooth) drops momentarily to about 1500rpm - Then it will cycle between ~1500rpm & ~2800rpm every second or two. What I've been looking for is any vacuum leak or an issue with the IACV. I think I've blocked all of the vacuum leaks & the behaviour doesn't change with the IACV off the engine entirely, port blocked & IACV still plugged in to the loom. What does make a difference is if I remove the vac hose that connects the MAP Sensor to the inlet. So with the MAP reading atmospheric pressure the idle drops to a steady but lumpy ~1200rpm. The engine does not have a catalytic converter or the 2-wire sensor that goes with it but is otherwise stock. I've wired the fuel pump to be on full time to eliminate it as an issue. The car does not have any auxilary systems, no air-con etc. Anyone got any ideas, I'll give any of them a go & report back. Quote Link to comment Share on other sites More sharing options...
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