My engine is detonating at around 2300rpms under moderate acceleration. The senario is this I drive from work (45min on the hwy), stop at the store for 20mins or so, stopped at light on a hill, accelerate moderatly heading to 50mph, when I get to 2300rpm the car detonates. I let off the gas and thn accelerate again no detonation. Any ideas?

My car:
95 GLE 131K, 120k service done, new knock sensor, no check engine light, 93 octane in tank.

 

Things that cause detonation in our cars:

Bad coil packs
Excessive carbon build up
Faulty or leaking fuel injectors
Spark plugs (please use NGK)
Dirty air filter
Bad gas - try another brand.

 

Thanks for the suggestions

Some more info:
Carbon - ran a tank of BG 44K car still detonates
Spark plugs - OE Nissan platium so they are NGK
Air Filter - New at 123K
Gas - 93 Texaco (use same gas in my Z no issues)
Fuel injectors - how do I tell if they are leaking?
Coil pack - if bad wouldn't the SEL be on?

Thanks
Chris

 

Check your ECU for the 0304 knock sensor code.

 

oops...missed in my last post...ECU code 0505...no failure

 

What Octane Gas do you use???

 

Always 93 octane

 

at least it dont BLOW UP

 

i had detonation in a ford ranger that was caused by the MAF sensor....but ford used MAF for determining their fuel delivery in that vehicle.

make sure your crank position sensor isn't damaged...it mounts directly to the oil pan so can't really shift, but maybe got hit by a stone. Make sure the knock sensor tests ok. Did the dealer give you the right heat range plug, should be a 5? Maybe try a BKR6e-11 and see if that helps. if you aren't throwing any codes i would guess that O2 sensors are good.

I had another vehilce with severe detonation and the mechanic ran a carbon cleaner (Motocraft "tune up carburetor cleaner") through it....you actually let the engine suck it in through a vacuum line until it stalled. let it sit for 1/2 hour then fire it up again and feed in a little more...then drive the pants off it...smoking like crazy the whole time. made a huge difference in that case. i think some service centers do something similar called a "motor-vac", which is different than a fuel injector cleaning....either might help

good luck.

 

3M makes an intake system cleaner similar to what your describing. It's a 3 step system that cleans the entire intake plenium with a foam, then suck another car via a vacuume line into the combustion chambers. It's new on the market and you need kit to adapt it to your vehicle. Ask around at some local service stations to see who has this system. Excessive carbon build up in the intake and combustion chambers will cause detonation. A simple fuel additive is really not going to clean that up, it's more of preventitive maintenance.