Guest 2slo4u Posted July 11, 2004 Share Posted July 11, 2004 Does anyone know the best ways to find a vacumm leak? I've tried: -using tubing to hear -spraying soap solution(wouldn't this just suck in and not make bubbles because engine is under vacumm?) -spraying wd40 to try to hear engine speed change, doesn't happen -don't want to try starting fluid, seems dangerous Any suggestions? Is there a way to pressurize the crankcase and rest of the engine safely to use soap solution and find bubbles? Can't seem to find why my engine idles too high (1100 rpm) AFTER warming up? Engine also misses a little at idle and at about 1500-2000 rpm seems to have a wall in acceleration, like lack of fuel. I've tried: -Adjusting afm tension, does not affect miss, only makes idle rich or lean -again can't find any vacumm leaks -valve lash within spec. -good plugs, wires, rotor, cap -timing 20deg. My car is 81zxturbo Any help appreciated mucho Quote Link to comment Share on other sites More sharing options...
datsunlover Posted July 11, 2004 Share Posted July 11, 2004 I believe the zx's computer is simmilar to the earlier systems (like my 75) and has a 'limp' mode. Mine did this when I got it. It idled a bit high, burbled a bit, reved good, but at about 2200 it would shut down. This is the computer going into 'limp' mode.. because it gets a bad/no signal from a sensor and it switches to a closed loop (I believe this is what it's called). I dono where to tell you too look thought man.. could be one of several sensors acting up.. check all the conections to the sensors/computer/ect... maybe try the 'tap' test on the computer; Take the panel off so you can see the computer (drivers side foot well) and with the car running, tap the computer box with your knuckles and see if the idle changes or the engine misses as you hit it.. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 12, 2004 Share Posted July 12, 2004 It is perfectly safe to use carb clean to check for vacuum leaks. Just spray it anywhere that you might think there is a leak and listen for a change in the idle. I dont know if WD40 works the same but I have never heard of anyone using that to check for leaks? Guy Quote Link to comment Share on other sites More sharing options...
datsunlover Posted July 12, 2004 Share Posted July 12, 2004 Yah, I've used WD40 and it works fine. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 12, 2004 Share Posted July 12, 2004 Doesnt WD40 kind of leave a mess though? Its more of a lubricate than a cleaner? Guy Quote Link to comment Share on other sites More sharing options...
dmyntti Posted July 12, 2004 Share Posted July 12, 2004 Another common approach is to use propane from a small propane bottle. Just attach a rubberhose to the end of the nozzle and use the other end of the hose to search for the leak. I find this works better than carb cleaner and have never had a problem with it. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 12, 2004 Share Posted July 12, 2004 The method I've been using (a lot recently too) on fabricated intercooler setups (most of them done poorly) is to made an adapter and pressurize the entire intake system with compressed air to ~20psi using an air compressor. While holding that pressure I use soap and water on all the connections to check for leaks. Usually people that don't think they have leaks are amazed by the amount I can find in their piping this way. Especially with a MAF/AFM system this can be a big problem. I made a simple round adapter that clamps into a hose coupling, and has a connection for my air hose on it. I usually remove the air filter and insert this adapter/coupling, clamp it on and test. Actually I recommend ANYONE running an IC to try this out, you'll be surprised with what you find. Quote Link to comment Share on other sites More sharing options...
Afshin Posted July 13, 2004 Share Posted July 13, 2004 Great idea Drax. Quote Link to comment Share on other sites More sharing options...
Guest 2slo4u Posted July 13, 2004 Share Posted July 13, 2004 I'll try pressurizing the engine. I was just afraid of popping crank seals out. I guess low pressure won't pop them out. I'll probably have to cap off the exhaust to keep a little more of the aire from leaking out during the test. Thanks we'll see what happens! Quote Link to comment Share on other sites More sharing options...
Tim240z Posted July 13, 2004 Share Posted July 13, 2004 I wouldn't pressurize the engine....... Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 13, 2004 Share Posted July 13, 2004 Pressurize the intake system... not the engine. Quote Link to comment Share on other sites More sharing options...
Guest stpdfst_in_TN Posted July 13, 2004 Share Posted July 13, 2004 i recently washed my stock motor in the 280z and it went into "limp" mode untill everything dried out overnight...never did find the actual cause. my mechanic friend has a machine that you hook up to the engine that makes smoke and pumps it into the crankcase...it helps you find vac leaks works very well...maybe you can find someone in your area that has one... they are alittle expensive for the do-it-yourselfer. http://www.industrialtoolstore.com/c/Champion-Engineering/-436148.htm Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted July 23, 2004 Share Posted July 23, 2004 How do you pressurise the intake but keep air from going out the exhaust? Is there a point where all the exhaust/intake valves are not open to exhaust? or do you plug the exhaust? I'm interested in trying this. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 23, 2004 Share Posted July 23, 2004 Just pressurize from your turbo outlet onwards. Don't worry about cylinders or valves, just keep your throttle plate closed and that will take care of it. I pressurize from the airfilter to the throttle plate usually and just check for leaks between those points. Air will only escape the system through vacuum leaks and any cylinders in valve overlapping position, which isn't much on a turbo cam at all. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.