detonation

[James]

I need some help on detonation (pinging). My 95ti is starting to ping more and more during hot summer days on heavy load 1st and 2nd gear (using Ultramar 91 Octane). I went to my mechanic last week and spent the entire afternoon (3 hours) and to this day, the mechanic and myself are still puzzled from this problem. We have changed the plugs from BOSCH platinum 4 to good NGK something (don’t worry there good ones, I just don’t remember). Went for a test drive, still detonation on heavy loads on 1st and 2nd. Even went to the local BMW dealer to have a discussion with the other mechanic about this engine ((hey guys this is a good one for the 318ti) comments from the dealer mechanics, this engine is trouble free, it’s one of the best engine ever built form BMW)
O.K. that does not help my detonation problem but it’s good news. We have in Canada a 94 Octane from Sunoco, guess what, it kind of solved my problem.

Does anyone know anything else that could cause this detonation, 94 Octane is my current fix.

See ya

[ZeroG]

Originally Posted by James

I need some help on detonation (pinging). My 95ti is starting to ping more and more during hot summer days on heavy load 1st and 2nd gear (using Ultramar 91 Octane). I went to my mechanic last week and spent the entire afternoon (3 hours) and to this day, the mechanic and myself are still puzzled from this problem. We have changed the plugs from BOSCH platinum 4 to good NGK something (don’t worry there good ones, I just don’t remember). Went for a test drive, still detonation on heavy loads on 1st and 2nd. Even went to the local BMW dealer to have a discussion with the other mechanic about this engine ((hey guys this is a good one for the 318ti) comments from the dealer mechanics, this engine is trouble free, it’s one of the best engine ever built form BMW)
O.K. that does not help my detonation problem but it’s good news. We have in Canada a 94 Octane from Sunoco, guess what, it kind of solved my problem.

Does anyone know anything else that could cause this detonation, 94 Octane is my current fix.

See ya

Do you have any performance mods? If so that could be part of the issue, if not here are some idea's. Detonation is caused by preignition in the cyl. so on the upstroke the fuel is ignighting cause a ping or a knock.

Now there are a few things that could be going on. You said that the 94' Octane reduced the issue, so you most likely have too much ignition timing during acceleration in first and second gear. Have you hooked up a OBD scan tool to the car? If so do you the knock sensor working correctly when the car begins to detonate? (As soon as you hear it, the OBD tool shoulc flash the word knock on the read showing you that the timing is being retarded to compensate.

On a hot say you are bound to have detonation everyone does. The excess heat just casues the car to run leaner and the only way to stop is to have some kind of cooler for the intake tempeture (Water Injection) or to run higher octane fuel. I would also check out the rest of your fuel system why your at it. Pump, Filter, Injectors...

Good Luck,

-Chad

[James]

I have no modification on this Ti, everything is stock. We did do try to test the knock sensor but I'm not sure it was efficient. Very primitive I would say, a few knocks from a hammer on the sensor and some type of light gyroscope to see if the belt would change it's timing. My mechanic was not sure if the BMW cpu was smart enough to detect a hammer, but it did not associate a hammer to knocking because there was no change on the gyroscope light on the belts.

Another indication that the knock sensor is possibly still good, I've got no engine codes. I've previously had an engine light for knock sensor about 4 years ago and we since installed a new one.

I guess I will take your advice, as soon as I have the chance I will hook up an OBD scan and maybe find the answer. Until then, I use Sunoco 94 Octane, and have no detonation.

Thanks
James

[sacramentophil]

Nothing is more aggravating to me than pinging. Well, interior rattles are a close second, but at least they're not going to destroy the engine.
Here are a few things I can think of off the top of my head...
-Carbon build-up in the combustion chambers (how did your old spark plugs look?) This will increase compression ratio and can cause detonation.
-Vacuum leak somewhere on the intake side. This will cause the engine to run lean.
-As Chad mentioned, check out the fuel system. Clogged injectors or low fuel pressure will cause a lean condition.
There are many more things that can cause pinging...I have a great website about it bookmarked on my other computer, I'll post back with a link.
I'm not yet familiar with any of the specific details of these engines, but I'm guessing that the ignition timing is not adjustable...is it?
How about a malfunctioning EGR valve?
If the 94 octane gas is helping, then by all means you should keep using it. But, remember that it's only a mask and you have a problem that really needs to be rectified.

Good luck,
Phil

[Jeff Spooner]

BMW's do not use a EGR valve persay. they use a Vent valve which is located on the back of the intake with a hose that runs from it to the valve cover. The valves are famous for failing and the hose spliting right where you cant see it. If your local shop has a smoke machine have them test for vacume leaks first. the vent valve will make a high pitch squealing noise most of the time when it goes bad.

[sacramentophil]

Here's that link regarding detonation & preignition: http://www.misterfixit.com/deton.htm

[Freedy]

If the car was running rich during that period the knock sensor was busted, there is a possibility that you have alot of carbon buildup in the chamber. This will cause pre-ignition due to the increased compression ratio. Has your car been noticeably more peppy than other stock Ti's?? You might consider trying a fuel additive that advertises chamber cleaning.