Clattering Valves??

[Libraman2k1]

I recently posted some concerns about my engine clattering at cruising speeds and now I have an answer from Infiniti--they found that my car fuel pressure is fine at idle but drops off below specs at acceleration which causes my valves to clatter from a lean air/fuel mixture--what do u guys think?--fuel pump or fuel pump control mod?--the fuel pump is humming louder than usual when the car is running and my valves dont start clattering unless the car is warm--if u guys think the FP modulator is the problem--where can I get used 1?--thanks

[DAEDALUS]

Probably the pump. I'm missing something here...maybe something really basic. How does low fuel pressure feed back to clattering valves?

[vanmeter]

sounds like oil pressure dropping off not fuel;fuel should not effect valves enough to make that much noise and car would lose power as well

[911/Q45]

I think you've mistaken knocking for clatter, that could be caused by a lean mixture, especially when it's hot. I'd replace the pump.

[Q45tech]

25 psi when the ecu expects 43.4 psi would be 25% less fuel per injection squirt............that would equate to around 15:1 AF enough to cause a lean acceleration miss.......knock.

[Libraman2k1]

ok guys- i think that i am speaking of valve "clatter" or "knocking" caused by a lean mixture--valves were checked by Infiniti--they seem to be ok--just a lean air/fuel mixture--I will try the fuel pump before I try the fuel pump controller-btw, if anyone knows where I can get a used FP control modulator, let me know--thanks--Reggie

[Mayhem_J30]

Check with one of our sponsors, http://www.infinitipartsusa.com for parts you need.

[Q451990]

I wouldn't worry about the fuel pump controller yet, until you've replaced the pump. The usual failure mode on the controller is that the connectors or leads on the circuit board will overheat and cause cold solder joints... you should be able to visually inspect it for problems.

How did the dealership diagnose the lean mixture? Have the injectors been flushed recently? If not I'd lean toward the pump, then have the injectors flushed and filter replaced. Do a search on the "power balance" test with Consult for how you can see your results after you're done. Each cylinder should have the same or no more than 12RPM variance when everything is perfect!

Heath

[Libraman2k1]

I appreciate it chris and heath--will put that pump on this week--thanks again--