Pinging issues

[weeves]

My 2006 LS developed pinging issues a couple of weeks ago and I can't figure this one out. It pings on medium/heavy loads when the engine reaches normal operating temp and sounds terrible at 75%-100% throttle.

I first noticed it after filling up at a gas station with 91 octane and thought it was due to bad gas. It could have been pinging before that because my stereo is usually cranked all the way up. I found one of the few gas stations in my area that sells 93 octane and filled up 3-4 times with no improvement. The only work I did prior to the pinging issue was installed a K&N drop-in filter, replaced DCCV and disconnected the battery.

I noticed a high pitched noise which sounds like it's coming from the throttle body area (assume normal?) which is more apparent when the engine is cold. I've sprayed carb cleaner all over the intake and vacuum lines with no change in idle. My buddy has a smoke machine which I want to use but he lives 2 hours away.

I've got no codes, average 23 mpg city/highway, coolant/air temp are normal, timing appears to be fine, o2 sensors are cycling back & forth like normal but it appears to be a little slower than my other car which may be due to the slower baud rate of my scanner. Vacuum holds steady at 23 in/hg. I inspected the plugs and the electrodes are a normal tan-ish color. Maybe a couple of them appeared to be running a little lean.

Thing's I've tried:

-RedLine SI-1 fuel injector cleaner (3 bottles)
-SeaFoam (Intake)
-NGK Iridium Spark Plugs gapped @ 0.040" (old Plat. plugs still looked new)
-New Ignition Coils (8)
-New Motorcraft Fuel Filter
-New Motorcraft Air Filter
-New MAF sensor
-Cleaned EGR valve

While I had the EGR off, it had minor carbon build up and the valve moved freely. However, I couldn't get the valve to move while applying vacuum to any of the ports. Is the EGR valve electronically activated? It looks like there is a MAP sensor mounted on top of it - is this right?

I'm thinking about buying a new EGR valve, knock sensors, and primary o2 sensors but honestly I don't know if those things will fix the pinging at all.

Thanks.

 

[joegr]

There is an electric solenoid valve built into the EGR assembly. The EGR valve won't move unless the solenoid is powered and vacuum is applied.

 

[weeves]

Ah, now that makes sense. The EGR valve's I'm familiar with, the vacuum source comes from the EGR solenoid. On the LS, it comes directly from the intake manifold.

The top vacuum port on the solenoid, it doesn't hold vacuum. Is it suppose to hold vacuum?

 

[weeves]

Update: I disconnected both the primary (upstream) o2 sensors and the pinging is 90% gone. Made a few WOT runs without any pinging but I noticed it a couple of times where I accelerated quickly while cruising. New Motorcraft o2 sensors are on the way.

 

[weeves]

Fixed!

I replaced both o2 sensors and it made no difference. I did, however, notice that the o2 sensors cycle a bit faster on my scanner. I still don't understand why the pinging virtually disappeared right after disconnecting the o2 sensors. The next morning, it was pinging like a sieve.

These ended up being the culprit:

I looked through the service manual but couldn't find anything regarding troubleshooting the VCT (variable cam timing) solenoids . So I ended up checking the resistance and they were both around 7 ohms which was probably ok. However, after I disconnected the solenoids, the pinging was 100% eliminated. I thought about throwing my old ones in my ultrasonic cleaner thinking it may have clogged oil passages/screen but R&R of the D/S valve cover is a major PITA so I decided against it and bought new ones from RockAuto.

The new solenoids finally arrived yesterday and I installed them right away. No more pinging and now I can finally drive my car again.

 

[joegr]

Thanks, good to know.

 

[scjmc]

Yes, thanks for actually posting the resolution like so many others do not.