bumble zee Posted May 2, 2003 Share Posted May 2, 2003 HELP!!!! I am stuck at 12 psi. I have a 76 280z, with a 81zxt engine. I am running the stock ECU and wire harness. I have Volvo IC. When i turned up the boost to 15 lbs once in a while in second gear the car would shake and backfire out the intake. it will do this like 1 out of 3 times accelerating. My a/f guage goes all the way into the lean. But why only sometimes.. and the other gears i can hold it out fine. I also have a turbo xs rlf bov... could that be leaking?? I have 2 washers shiming it. What could it be?? any ideas?? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted May 2, 2003 Share Posted May 2, 2003 If your BOV is venting all your boost, you will get too much fuel - this has the effect of cooling the O2 sensor enough to shut it down, and it looks lean, but it's really wet! Quote Link to comment Share on other sites More sharing options...
lifegrddude Posted May 2, 2003 Share Posted May 2, 2003 How's your fuel system? Stock injectors might be getting maxed out. Check the plugs to see what the problem is too. John 82ZXT Quote Link to comment Share on other sites More sharing options...
yo2001 Posted May 2, 2003 Share Posted May 2, 2003 Check and see if the if the BOV closing fast enough. I don't if that's the problem but could be the BOV is creating a small vacuum leak. Quote Link to comment Share on other sites More sharing options...
bumble zee Posted May 3, 2003 Author Share Posted May 3, 2003 i have 370cc injectors out of a svo mustang, and a alluminum fuel rail. i am running a 84 300zx fuel regulator. Quote Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted May 3, 2003 Share Posted May 3, 2003 Under wide open throttle the ECM does not respond to the 02. You do have a good hi pressure fuel pump in this car right? Add a fuel pressure guage and make sure your not loosing fuel pressure. If you have the SVO injectors it should go way rich all around. Sounds like your out flowing the pump. Let us what you find. Quote Link to comment Share on other sites More sharing options...
Len Posted May 3, 2003 Share Posted May 3, 2003 You were right. I believe Its you stock pop off valve. Mine did the same thing. You hit too much boost in 2nd gear at high rpm. I went ahead and installed a pipe plug where the pop off valve was. Also some of the ZXT's have a rev limiter at around 6000 rpm. Shuts everything down at that rpm. But sounds like you might just put another washer if not take the pop off valve off altogether. That is only if you feel secure with your boost adjuster not giving an overboost situation. my 2 cents. My disclamer is I am not responsible for any damage that may be caused following my reccomendations (especally after I had a few beers Len Quote Link to comment Share on other sites More sharing options...
bumble zee Posted May 3, 2003 Author Share Posted May 3, 2003 i have the stock zxt fuel pump. And i dont have a pop off valve... i am running my 76 intake. no air regulator, no emmisions what so ever. I turned my boost down to 12 tonight... i am going to try a few things tommarow. thanx for your thoughts!!! keep em coming Quote Link to comment Share on other sites More sharing options...
Len Posted May 3, 2003 Share Posted May 3, 2003 Is your BOV venting to the atmosphere? That could be a problem showing lean. Quote Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted May 3, 2003 Share Posted May 3, 2003 Forget trying anything else, replace that fuel pump. It was only designed to produce 180hp on a 25lb injector. It should have been the first thing you replaced. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted May 3, 2003 Share Posted May 3, 2003 Alex does have a point. I blow a head gasket with a stock fuel pump @12PSI. Quote Link to comment Share on other sites More sharing options...
Len Posted May 3, 2003 Share Posted May 3, 2003 True. But Before you do that run a liquid filled fuel guage into your cab. Do your WOT. See if you lose fuel pressure at max. boost to verfy your fuel pump is not up to job at hand. Your are pushing the envolope on fuel pump but seem to remember Scotty-miz running 18 psi boost on 370's using stock fuel pump (not sure). Although fuel pump would be a good upgrade for future. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted May 3, 2003 Share Posted May 3, 2003 Is your BOV venting to the atmosphere? That could be a problem showing lean. It would be RICH if it was venting under boost. And the O2 meter registers lean because it's cold and wet with fuel. Trust me on this if you don't believe me. It could also be your fuel pump crapping out as well - the stockers really do suck for flow at higher pressure. Quote Link to comment Share on other sites More sharing options...
Len Posted May 3, 2003 Share Posted May 3, 2003 Sleeper I was agreeing on your first post (seeing if BOV was venting in atmosphere) Quote Link to comment Share on other sites More sharing options...
bumble zee Posted May 3, 2003 Author Share Posted May 3, 2003 my friend fixed my problem for me... needed more washers in the bov... now it runs fine.. but have alot of boost spike... hits 15, then drops to 13... i am told that that could be the boost controller. Quote Link to comment Share on other sites More sharing options...
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