: Pinging above 3000RPM with 93 octane

02-16-08, 11:28 PM
I just purchased a 2007 Cadillac DTS with 30,000 miles (Cadillac Certified). I took delivery of the vehicle with regular 87 octane fuel. There was noticeable pinging, so I went with higher octane fuel at the next fill up. I have now gone through 3 tanks of 93 octane Shell with Chevron Fuel System Cleaner - there is less pinging but it is still noticeable.

At above 3000RPM and more than 25% throttle, I hear the pinging. Less throttle or fewer revs and I can not hear it. It does not seem to vary with engine temperature (it occurs hot and cold).

I have spent some time thrashing the engine, but the pinging has not improved.

This doesn't seem to fit the carbon knock that I have read about. Or does it?

Any recommendations?

02-16-08, 11:34 PM
I run 87 and no pinging.

That is not cold carbon rap.

Since it is certified, take it in. might be a bad knock sensor. Have you checked the DTC's?

02-16-08, 11:49 PM
I checked - no DTC's at all.

Crown Vic Owner
02-16-08, 11:56 PM
Take it in. Also, i am not sure about this, so dont take my word on it, try pulling the battery overnight to let the PCM relearn fuel trims and reset, it helps reset everything.My bet is bad gas (go to the same station by chance?), bad plugs, or a bad knock sensor.

I guess if they cant fix it, throw some seafoam in via the PCV vacuum line.

02-17-08, 11:46 AM
"Bad gas" is pretty far fetched, considering you said you're running Shell 93. Even if it were "bad gas", the knock sensor would retard timing to prevent detonation. The engine is rated to run on 87: my car runs to 132 on 87 and not a ping, so should yours.
The spark plugs are double platinum tip/electrode and are guaranteed for 100,000 miles.

If your car is GM Certified, let them deal with it. Do not dump seafoam or any other snake oil in the engine. If the dealer gets wind of that, your warranty is out the window. Read your warranty. Additives and potions are a no-no.

If the knock sensor is still under the intake manifold (as on earlier N*'s), let the dealer determine if something's wrong.....you take it apart, and see warranty, above.

02-17-08, 12:18 PM
I have filled up with Shell 93 at two different Shell stations that I trust, so bad gas is out.

Is valve adjustment problems common at all with N*?

02-17-08, 03:19 PM
Valve adjustment is a non-issue on a N* unless you have a collapsed hydraulic lash adjuster, which would make a rattle that would wake the dead.

Don't get creative: Take Ranger's advice and take the car back. Tell (TELL) the service rep that something is wrong, you're not happy, and fix it. You paid good money for the car and don't deserve to be jerked around !!

If you start fooling with it at this time, you'll very likely mess up your chance for a warranty fix.

02-17-08, 05:37 PM
Really, the only way you would be pinging above 3k running 93 is if you are running severely lean. It is likely fuel pressure related (fuel pump, clogged fuel filter, FPR, etc). Let them fix the problem. Don't romp on it until you get the problem fixed. I think it would be better if it blew up while in their hands.