Relay clicking sound when decelerating under load

[Mliving1980]

My 2001 QX4 is making a clicking sound similar to a relay sound when I let off the gas pedal after I have had to use heavy/high rpms (typically going up a hill, under load while towing and when I shut the car off from "coming in hot/fast" not sure what the issue is. Going to try switching the fuel pump relays and seeing if that helps.. also get the same type of clicking from the headlight ballasts (I think). It's mind boggling and numerous shops are all completely clueless. Could use a little help on this one! Thanks. Also, I'm available for any questions on anything as I have bad 3 different qx4's ranging in years frim 2000-03 and several engine swaps and encountered many issues all of which I have troubleshoot myself. In short, I know alot about the Q, but she never seems to quit stumping me with something new!

[mdmellott]

I'll take a swag at it. With little or nothing to go on, I will guess that your EVAP purge valve is freaking out, trying to stay open to suck up fuel vapor from the canister, in order to compensate for the lack of throttle command, to increase fuel demand when you let off the gas pedal but are still under a high load. Still freaking out, it does not want to stay closed as it should when you shut off the engine.

This is just a crazy guess. Imagination is a terrible thing to waste.

[Mliving1980]

I'm changing out purge valve solenoid as we speak. Ordered part last week (they sent wrong one, production months mistake) and will install. Hopefully you're right, I'll let you know of course and give you the credit on it . I also ordered a new fuel pump. Between the 2 parts, I think I should have a fix! Purge valve will go 1st! Thanks bruddah

[mdmellott]

If we made a lucky guess and it is a faulty EVAP purge valve that needs replacing, then it's a purchase well made. If it is an EVAP purge valve issue effected by an external electrical issue, intermittent or otherwise, there may be regrets on the purchase. The factory service manual can guide you through testing this. https://www.nicoclub.com/service-manual ... 5%2Fec.pdf I spend a lot more time reading these service manuals and other tech resources to figure out a solid direction to follow than I do with auto parts suppliers.