Piston Slap: Tapping and Clicking Fuel Injectors?
Walt writes:
Sajeev,
I wrote to you five years ago about a frozen Ranger parking brake, and later on about the incredibly dumb idea of purchasing a vintage Mustang with a loan. Thankfully, the former resolved itself, and the latter remained a pipe dream. What I did do, however, was buy a ’14 Mustang GT with a 5.0-liter Coyote V8 and six-speed manual. It now has around 9,800 miles.
At around 3,000 miles it developed a clicking noise at idle, audible with the driver side window rolled down and a curb or jersey barrier to bounce the sound back at me. The frequency of this click increases with engine revs. Existence of this issue with the 5.0-liter Coyote is well documented on F-150 and Mustang forums alike.
Theories range from “don’t worry about it,” to noisy fuel injectors, to normal operation of the variable valve timing system, or camshaft problems.
I haven’t noted any power loss or additional malfunctions, just the click. The only thing I have seen is oil consumption; about 3/4 of a quart over the last 5,000 miles or so. With forum posts that report anything from zero oil consumption to rates similar to my own, I don’t know what to make of it.
There doesn’t seem to be any technical service bulletins for such a problem. I am somewhat hesitant to take it in for unnecessary diagnostics and tear-downs if it’s a non-issue. However, if it truly is a ticking time bomb, I want to take care of it while the warranty is still in effect.
I would appreciate any insights you or the Best and Brightest may have to offer.
Sajeev answers:
Yeah, my 2011 Ford Ranger makes that fuel injector clicking sound too. It comes from the disc design (?) of newer fuel injectors, combined with the fact that computers normally dump extra fuel to keep a cold motor running. It’s the only logical reason I’ve seen for this phenomena, as it does cover a variety of makes and models over the last decade-ish.
I reckon you could disconnect a fuel injector when idling to see if the sound changes. It won’t hurt anything, as the old school EFI cylinder balance test has done this for years.
Speaking of old school, I was worried my 1988 Mercury Cougar would start that late-model tick after ditching the old pintle injectors for the discs (?) from a 2004 Mustang GT. Thankfully, they are silent — or perhaps Sanjeev got lucky after getting an old Cougar drunk late one night?
(BTW, this is what happens when you can’t find your roll of painter’s tape.)
[Images: Ford, © 2016 Sajeev Mehta/The Truth About Cars]
Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.
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I'm not a mechanic but I've been doing IT work for a small chain of auto repair shops for 20 years or so. I'm out in the shops very very often keeping the Tech 2's, IDS's, DRB 3's and Can scan tool stuff working. I see a lot of cars. Mostly broken cars. Seems to me that almost all modern engines, regardless of make, have injector noise. The quieter ones all have some miles on them. 80k or so. There's a sweet spot in there mileage wise when most engines seem quiet. I own two Town Cars. One has 147K on it and the other has 54k on the odo. The low mileage car has a fair amount of injector noise. Nothing overly objectionable but it's there. The 147k car is quiet as a mouse. You can hardly hear it idle at all. Never had the injectors serviced. They seem to "wear in" for lack of a better term. I don't know the how or whys but that's the casual observer take for what it's worth.
My Pentastar Challenger did this since brand new on the dealer's lot. I don't think much of it because my Crown Vic did it a lot louder.