Preignition on 2007 Tacoma, 2.7

I have 235,000 miles on my single cab, great truck, but lately, getting a lot of preignition when the engine is under demand, prior to downshifting. Even sometimes when downshifting. Don't have any codes. I checked the catalytic temps with an OBD II tester. At idle CAT11 - 692 and CAT12 - 624. Also O2 sensor readings: O2S12 - 0.680, and O2S11 - 3.285. Lacks power at times at speed, feels like it's under a load. Any ideas?

 

With that many miles you could have carbon buildup on the pistons causing a higher compression ratio and subsequent detonation. Check the compression and/or do a SeaFoam torture test.

 

Will the seafood torture test burn off the carbon if there is a buildup? The other thing I just remembered is a heavy exhaust/gas fumes at times right after you start it up.

 

How old are the plugs? And what kind? Have you checked to make sure they are all within spec and the coils are good? Seafoam should break up carbon build up and couldn't hurt even if thrre are other issues.

 

Ha! I just looked and saw that the auto spell checker changed my last post to "seafood" torture test. Anyway, I did the seafoam, but I still have pre-ignition. And yes, my spark plugs are from Toyota and for my truck. I still suspect the catalytic converter. But next, I am going to troubleshoot the knock sensor. Because if it's not working, it will not adjust the timing when it detects pre-ignition.

 

If you have an obd2 tester, you can see the timing in real time. Might be an easy diagnosis if you can get it to a parts store.