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Car starts but backfires and loss of power


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I have a 1977 280z, I have just finished doing body work and paint on the car and that will be in a later post. I am currently however having problems with a backfire out my tailpipe and what seems to be a vacuum leak. I have installed new injectors new plug wires distributor the list goes on and on. The car will be undergoing a engine transplant in the fall but I would like to be able to drive the car until then. I have posted a small 1 minute video of what the car is doing.

http://www.youtube.com/watch?v=9r2lZWDaTCs

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Have you tried spraying some carb cleaner (not the brake cleaner!) around and see when the RPMs will pick up? It sounds like the vacuum leak comes from the intake manifold gasket. I would also check the EGR valve which gets activated when the engine is hot (it should be closed at idle). FSM shows the tests how to check its operation.

 

You can also do the 'yogurt cup' testing that FastWoman used on classiczcars. Basically, you remove the intake rubber boot, put the yogurt cup with a small hole right into the intake opening, and pressurize your intake with compressed air (25-30 psi should do it). Then you just listen for escaping air. This is easier since the engine is off and there are no extra noises.

 

Regards!

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Thanks Darom bought a can of carb cleaner today and will be doing a vacuum test that way. On another note I seem to be having a problem with my front wheel bearings I have replaced them twice now and for some reason or another they keep chirping then the bearing eventually is no good. This is the second time I have replaced the bearing in a week. I am torquing the spindle nut to 25lbs of torque according to my fsm. Has anyone else had problems such as this before? I have been over to atlantic z and looked at the tutorial for changing them over there.

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I dont know about your engine trouble, but your bearings are WAY too tight if you torque the spindle nut to 25 FT/LBS and leave it at that! You have to torque it to 25 ftlbs then back it off an 1/8 to a 1/4 of a turn. You should be about to spin the disc/wheel freely. If there is ANY drag you will go through this again and again. Good luck.

Edited by fastzcars
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