QuestionQUESTION: Thanks, this nissan idles rough/misses. I have tried the following: plugs,wires,rotor,cap,dist,throttle sensor,oxy sensors,idle air valve,intake sensor,fuel pump, cleaned the throttle body,timing good,replaced 1 injector on #4 cyclinder. No drastic improvement. Nissan dealership say the fuel pump is bad cause the return line is pinched and it idles smooth.I did the same after the 2nd fuel pump and it smoothes a bit, but still idles rough. I tried throttle spray in the intake one side and then the other of the intake while the engine is running and the engine really idles smooth. With the service light on, the vehicle scans multiple cyclinder misfires.
Could it be a bad intake gasket, tried to tighten them a bit but no improvement.
ANSWER: Yes an intake gasket is most likely at fault, this intake leak usually sets a code for # 4 cyl misfire. It uses a paper gasket and it will suck it in near the #4 cyl. Its the gasket between the head and lower intake. Its a time consuming job ,and you might as well replace the knock sensor while you have it off. The knock sensor is on the back side of the block ( passenger side) it has one bolt securing it directly to the engine. As you noted above regarding the spray, a carb clean, or throttle spray you are using should work. With the engine missing, use the straw supplied with the spray, and spray in the area of the #4 cyl intake to head mating area if the miss goes away or idle fluctuates you will need to replace that gasket. Do not use any extremely flammable chemicals as they may ignite and start a fire!!!! Also, use factory gaskets as they have now been improved. Good job! not to many people understand the basics, if the gasket is sucked in thats a vaccum leak after the mass air flow sensor. Any extra air after that sensor will cause false computer readings. Good Luck
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QUESTION: would it be normal for the engine to be difficult to start after the intake gasket replacement. The fuel pump is new and it delayed for the initial start up. The engine runs smooth at idle and on the road. Set the timing at 20 and set the idle back down to 750-850.
This solved the problem, thanks for the information.
AnswerIf you disconnected the fuel line then yes. It will take a little time for the pressure to build-up to properly flow out of the injectors. Also, always double check your work! Make sure that the intake hose is tight and fully seated all the way around the throttle body. I have seen the hose rolled underneath where it is hard to see causing a leak. Good job!
