Shiboh Posted July 17, 2020 Share Posted July 17, 2020 I have heard many times that these l28 EFI engine will stall if you remove the dip stick/ pcv hoses while the engine is running, however mine will stay running without any of those things in place. Does anybody know why that would be? I recently replaced the pcv valve to see if that was it but that made no difference. I've been told vacuum leaks will cause this however my manifold vacuum readings are proper through the whole rpm range. Starting to think it's gotta be piston rings or something... Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 18, 2020 Share Posted July 18, 2020 It will only die if the air-fuel ratio is about right, and that's when you remove the oil filler cap. If it's running rich then the extra air from removing the oil filler cap (not the dip stick tube), won't have any effect. The dip stick tube is a source of vacuum leaks through the PCV system, but it would probably only change idle speed a small amount if you pulled it. Try removing the oil filler cap and see what happens. Quote Link to comment Share on other sites More sharing options...
Shiboh Posted July 18, 2020 Author Share Posted July 18, 2020 @NewZed So then my engine would be running super rich, right? I have tried removing the dipstick, oil cap, and both PCV hoses. I have even tried removing all at the same time and the engine still ran. I don't notice any change when removing any or all of these things. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 18, 2020 Share Posted July 18, 2020 Define "super". The filler cap test is more of a confirmation that things are right. If it dies then the air-fuel mix at idle is about right. But it doesn't really tell you how bad things are though, if the engine keeps running. My engine used to run fine, and smell fine, not rich, with the filler cap off but would not pass emissions. I had to put an old factory AFM on to get it to pass. Quote Link to comment Share on other sites More sharing options...
Shiboh Posted July 18, 2020 Author Share Posted July 18, 2020 @NewZed Well I recently swapped to FAST's EZ EFI and am still working out the kinks. I know it runs slightly rich sometimes but to what extent I'm not sure at this point. I've blown injectors on previous tunes but I seem to have that figured out. My engine only smells rich on first startup. When warm there is no gasoline smell and a/f seems good. I am thinking that the electronic IAC supplied with the EZ EFI kit is compensating for the change in vacuum when removing the oil cap/ dipstick, etc. When I first got the car I removed the oil cap to check for vacuum leaks and it died, now with new EFI it doesn't. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 19, 2020 Share Posted July 19, 2020 Most "learning" EFI systems take multiple start, warmup, and cool-down/restart cycles before the parameters are properly set. They don't learn everything on the first pass. Rich is safer than lean so I'd expect them to start rich and lean things out based on O2 readings as time goes on. You could just drive it and keep a log and see where things go. Any changes you make will upset the learning process. Even on modern cars, you're supposed to start the engine cold and let it warm up fully, no throttle input, if you reset the computer. It's part of the learning process. Quote Link to comment Share on other sites More sharing options...
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